TESTING PRECIOUS METALS

Gold, Silver, Platinum Metals

Identifying - Buying - Selling

A Handbook for the Jeweler, Dentist,

Antiquarian, Layman

By G. M. HOKE

Author of Refining Precious Metal Wastes

THIRD EDITION

T H E JEWELERS' TECHNICAL ADVICE COMPANY

New York, N. Y.

COPYRIGHT 1946 BY C. M. HOKE

All rights reserved. This book, or parts thereof, may not be reproducedin any form without permission of the publishers.

The First Edition was originally published inThe Brass World—Plating—Polishing—Finishing

of New York

Parts of the Third Edition were published inThe Jewelers* Circular-Keystone

of New York

PRINTED IN U. S. A.

THE JEWELERS TECHNICAL ADVICE COMPANY was founded in1912, when platinum was first coming into use as a jewelry metal.

Its manager, Sam W. Hoke, was a pioneer in the technology ofplatinum. He patented a series of oxygen-gas torches, used formelting and welding platinum, soldering gold and platinumjewelry, melting quartz glass, etc.

In 1912 the melting of platinum was possible in only a fewplants in the whole world; today it is a commonplace in even thesmaller jewelry factories.

C. M. Hoke, the writer of this book, has a background of uni-versity training in chemistry and biology, as well as experience inthe teaching of chemistry. For years she has devoted her time toinstructing jewelers and others in refining, melting, salvaging andfinishing the precious metals, and in developing equipment forthe control of compressed gases.

Foreword

The precious metals are always interesting—even the prosaictasks of testing, refining, working, and selling them command aperennial interest. For many years the writer has been concernedwith these matters, and the following pages are designed to answerone group of questions that has arisen time and time again.

If you are handling precious metal articles, you will often needto distinguish, for example, between a piece of 18-karat and apiece of 14-karat gold, or to decide whether a given article is whitegold or platinum. If you are buying or selling old jewelry or den-tal golds, you will often wish to know the approximate value of apiece, without taking time for an assay, and possibly without in-juring the article itself.

The purpose of this book is to describe methods, particularlythe touchstone method and its variations, that will give this in-formation.

The idea of testing gold with a touchstone is very old. We aretold that the Lydians used it in 500 B.C., rubbing the metal againsta smooth stone, then comparing the streak with similar streaksmade by metals of known composition. When during the MiddleAges men learned to make strong acids, the method became moreexact. During the last few years, with the introduction of themany new metals and alloys and combinations that now character-ize the precious metal industries, the method has been greatly am-plified. In the hands of a careful worker it yields quickly a largeamount of useful information.

These chapters will first describe the touchstone method as usedon the ordinary yellow gold alloys that have been in vogue sincethe days of our grandfathers. Then we shall cover silver, and thewhite golds and platinum alloys that came into use at about thetime of World War I.

Some other methods of identification that do not employ thetouchstone will also be described, and full attention will be givento those new alloys and combinations, including the ruthenium al-loys, which appeared during World War II.

The book does not discuss assaying (which is the chemical an-alysis of a small weighed sample) and it gives only a few paragraphsto the problems of the prospector. Its purpose is to assist thejeweler, antiquarian, metal buyer and layman to identify preciousmetal articles and estimate their value. A knowledge of chemistryis not required.

One chapter is devoted to quality stamps and karat marks. An-other contains advice not only for the layman with some jewelryto sell, but also for the jeweler or refiner who might buy it. Itoutlines the evolution of the gold-buying industry, calls attentionto the laws under which it operates, and suggests the problems,profits, and responsibilities that accompany it.

C. M. HOKE.

Palisade, New Jersey, 1945.

Contents

Foreword 7

Chapter I. The Old Touchstone Method and the Yellow

Golds 11

Chapter II. Silver and Some Other White Metals 18

Chapter III. The Quality Stamp—"Let the Buyer Beware!" 29

Chapter IV. The Platinum-Group Metals and the WhiteGolds 39

A. New Metals; Old TestsB. New Metals; New TestsC. Some Other Tests

Chapter V. Buying and Selling Old Precious Metals 63

Chapter VI. Some Paragraphs for the Prospector 78

Appendix 83

A. A List of Equipment.B. When Handling Strong Acids.C. How to Determine Specific Gravity.D. A Table of Metals, their Melting Points and Specific

Gravities, and their Responses to Acids and to theOxy-Gas Flame.

E. Some Definitions and Formulas.

Index 91

CHAPTER I

The Old Touchstone Method and the YellowGolds

THE equipment for testing ordinary golds is shown in thefrontispiece, though most workers will add one or two more

acid bottles. There is the smooth, flat stone, of slate or fine-grainedbasalt; there are the so-called needles—pointed bits of yellow goldof various finenesses, each marked with its quality; a small triangu-lar file; and the acid bottles. The gold buyer will need in additiona scale and a set of weights.

Our first task is to make sure that the article to be tested reallyis gold. We then determine its quality by rubbing it upon thestone so as to make a mark or streak, and comparing this streakwith streaks made by the standard needles. This in one paragraphis the whole story of the touchstone tests.

Let us first acquaint ourselves with the ordinary, old-fashionedgold alloys of a golden color, postponing our examination of whitegolds, silver and the platinum metals until later. For your firststep, obtain several articles of different types, but of whose qual-ity you are sure; for example, a genuine gold coin or a piece or twoof high-grade jewelry made and stamped by a reputable manufac-turer; some moderately-priced articles; a handful of very cheapnovelty jewelry that is finished to look like gold; and finally, forcomparison, a piece of clean brass. The more articles, and thelarger their variety, the more quickly you will learn to identify andappraise the "unknown" articles that will come to you.

THE FILE

The experienced gold-buyer always begins by filing a deepnotch in the article, in order to penetrate any outer layers, and hemay learn immediately that the gold is only skin deep. Medium-priced jewelry—rolled-gold or gold-filled goods—consists of a coreof inexpensive metal to which an outer layer of karat gold has

been affixed. The core is usually brass; occasionally it is a gold al-loy of lower karat; and during World War II use was made of asterling silver core, instead of brass, because wartime regulationsforbade the use of brass for jewelry manufacture. Low-pricednovelties are apt to be electroplated and their surface film of pre-cious metal is very thin indeed.

Most high-grade articles are flash-finished with a light electro-deposit of pure gold, and when new may be further protected bylacquer. While these latter films can be removed by a few strokesof the file, the heavier coatings, such as those found in gold-filledor rolled-gold goods, are pierced only by a deeply-filed notch. Ac-cordingly, as we said, the experienced buyer always begins byfiling a deep notch.

NITRIC ACID

The first acid bottle contains chemically pure (C.P.) nitric acid,full strength, which can be bought from a drugstore or supplyhouse. This acid attacks the majority of metals, and will destroyskin, clothing, woodwork, and so on, and therefore must be han-dled with care. If you should get acid on your skin or clothing, im-mediately wash it off with much water—hold your hand under thefaucet and let the water run on it freely—and very little harm willbe done. If no running water is nearby, provide a basin of waterfor immediate use if needed.

Note that the glass stopper of the acid bottle is extended into along tongue. With this tongue, apply a small drop of nitric acidto each of your metal articles, on a clean surface or in a freshly-cutnotch, and watch the results, noting the color changes, if any. Aftera half minute, rinse the acid off with plenty of water, dry, and seeif the metal has been attacked.

Brass or copper boils up instantly and the acid turns green. Goldof 6-karat# or lower will be attacked almost as promptly, and willshow a green color, due to the copper with which it is alloyed; 10-kwill darken; ordinary gold of 12-k or better will show little or noreaction.

* The term karat means a twenty-fourth part, and expresses the proportionof gold in an alloy. Thus pure gold is 24-k; 6-k gold is 6/24ths (or i/4) gold, theremaining i8/24ths being some other metal or metals. Pure gold is also de-scribed as "fine" gold, or as being "1000 fine," and 6-k gold is sometimes spokenof as "250 fine."

In general, any metal of the yellow color of gold that will standthis nitric acid test, may be assumed to be gold or a gold alloy.Note that we say of yellow color, for there are several white metals,such as platinum and stainless steel, that resist nitric acid.

If possible, get a friend to hand you some unstamped articles ofwhose quality he is sure; examine these "unknowns" and reportto him regarding their character, repeating the tests until you havelearned how the various metals and alloys respond to the acid test.

DETERMINING THE KARAT

When the acid test has convinced you that an unknown is indeeda gold alloy, your next step is to determine its karat, using thestandard needles and the touchstone. Rub first one needle andthen another upon the stone, thus making a series of streaks uponthe smooth surface. Each streak is a thin layer of metallic mole-cules—molecules of gold and molecules of base metals. Now withthe stopper of your acid bottle, draw a little nitric acid across eachstreak.

As you would expect, the base metal molecules, thus exposed tothe acid, will dissolve promptly, while gold molecules remain un-changed; hence, streaks made by the lower karat needles will al-most disappear, but those of higher quality will show little or noresponse.

Returning then to your unknown, rub it hard against the stone,making a streak. Suppose you suspect that it is about 10-k quality,maybe less. Beside the first streak make two others, one with the10-k needle, another with the 8-k needle. With the stopper ofyour acid bottle, draw nitric acid across the three streaks of metal.

Watch the way in which the acid works. As soon as you find astandard streak whose response is the same as that of your un-known, then you have found the approximate fineness of the un-known. By "response" we mean the speed and completeness withwhich the streak is attacked.

But suppose your unknown is of such high quality that it is notaffected by plain nitric acid. We must now turn to the secondbottle, which contains chemically pure hydrochloric acid, and weshall make up some aqua regia.

AQUA REGIA

Aqua regia is a mixture of nitric acid and hydrochloric acid.The name means royal water, and was used by the ancients be-cause the mixture dissolves gold, the noble metal. Practically thesame results are obtained by adding a little table salt to diluted ni-tric acid. When aqua regia is first made up, chlorine is evolved, anoxious gas which attacks metals and should not be permitted toreach machinery, balances, and so on. Nor should the mixturebe kept in a stoppered bottle, for the evolving gas might break thecontainer.

Because of this (and also because it spoils on standing) aquaregia should be made up only as needed. Mix it the same wayevery time; the exact proportions are not important, but get ac-customed to a certain mixture and continue to use it.

It is possible to mix the two acids right on the stone, after mak-ing the streaks; that is, draw a little nitric acid across the streaks,then add a little hydrochloric acid, letting the two acids run to-gether. This is not good practice, however, because each stopperbecomes contaminated with the other acid, creating confusion.

A better plan is this: With a medicine dropper measure out tendrops of nitric acid into a tiny bottle; add ten drops of water, pre-ferably distilled; then using a clean dropper add two drops of hy-drochloric acid. This gives you enough aqua regia for about adozen tests. Wash your medicine droppers after every usage.

Returning then to the streak that was not affected by plain nitricacid, wash and dry the stone, and apply aqua regia with a smallglass rod or a clean medicine dropper. Even fine gold is attackedby aqua regia. By comparing the response with first one standard

needle, then another, you can determine the quality of your un-known.

This test differs slightly in principle from the nitric acid test, inthat aqua regia dissolves the gold molecules as well as those of mostbase metals.

Some workers make up their aqua regia with even more waterthan above, because the reactions proceed more slowly with thedilute mixture and therefore are easier to compare. Some workersuse a different proportion of hydrochloric acid.

Note the color changes. Fine gold when dissolved gives a yellowcolor, but this is usually masked by the green color of the copperthat is almost always present in gold alloys. Nickel, used in mostwhite golds, also gives a green color. Silver when treated withaqua regia, forms a cheesy white substance on the stone which maywell confuse a beginner. Because of the influence of the alloyingelements, it is well, if possible, to use yellow gold standard needleswhen testing yellow gold unknowns, green gold needles with greengold unknowns, and so on.

GREEN GOLDS

Green gold alloys, especially those of high quality, contain con-siderable silver and little or no copper. The response of silver toaqua regia is peculiar, as we shall find in a subsequent chapter.Green golds respond more slowly to aqua regia than yellow goldsof the same karat, and may lead you to think that they are more

Standard needles for testing the quality ofwhite golds and green golds.

valuable than they are. Therefore, we repeat, when testing greengolds, use standard needles made with green gold points.

RED GOLDS

These alloys contain more copper and less silver than the yel-low golds of the same karat, and respond slightly more rapidly toaqua regia.

WHITE GOLDS

A white gold is an alloy that contains enough of some whitemetal to destroy the yellow color. There are two whiteners in gen-eral use—nickel and palladium.

Most inexpensive white golds consist primarily of gold andnickel, to which copper and zinc may be added, sometimes othermetals. When testing them, use the same procedure as with yel-low golds, but it is wise to use standard needles made with pointsof white gold.

Many better quality white golds consist of the same elements,gold, nickel, and small amounts of other base metals. However,many white golds of especially fine quality, including many dentalalloys, are whitened with palladium.

Now there is considerable difference in the value of gold-nickeland gold-palladium alloys, assuming that the proportion of goldis the same. Hence your concern, after deciding that a given ar-ticle is white gold, is to learn what kind of white gold it is—nickel-gold or palladium-gold. This takes us to a later chapter of thisstory, in which we cover palladium and nickel.

DENTAL ALLOYS

There are dozens of dental alloys in use, ranging in value fromiridio-platinum pins, through the wrought and casting golds andhigh-karat solders, down to the amalgams, base metal "technic"alloys, and occasional pieces of stainless steel and aluminum thatmay find employment in dental work.

Some dental fillings are almost pure gold. If a piece of yellowmetal has been in use in the mouth for some time and still presentsa tarnish-free surface, it probably is gold of good quality, andshould respond to the acid and touchstone tests in much the samemanner as the jewelry alloys. Do not be deceived by the word

solder as used in dentistry; it may refer to a gold alloy of high value,used to join together the parts of a denture.

The tendency today is away from the conspicuous yellow goldsand toward the white alloys—white golds and alloys containingplatinum-group metals—which will be discussed fully in a laterchapter.

Dental golds do not carry the quality stamps that are commonlyfound on jewelry, hence gold buyers who distrust their own abilityto appraise metals often refuse to quote on dental alloys. For thatreason the buyer who can appraise properly, will find excellent op-portunities in this field.

Clean the stone frequently to remove all marks, perhaps by rub-bing it with fine pumice, or by covering the spots with a little aquaregia. Wash it free of acids before putting it away, or the traces oftoday's tests may confuse you tomorrow.

A list of the equipment used in these tests will be found in theAppendix.

The Appendix also contains a table of metals with their meltingpoints and specific gravities, as well as their responses to nitricacid, to hydrochloric acid, and to the oxy-gas flame.

CHAPTER II

Silver and Some Other White MetalsT^HIS is the group that offers the greatest challenge to the pre-J- cious metal buyer, and can offer him the greatest profit. It

includes on one hand the silver alloys, the white golds and theplatinum metals, and on the other hand a vast array of alloys likestainless steel, which, though handsome and useful, are not pre-cious metals. The purchaser wants to be able to separate out,from a trayful of white metal articles, precisely those that are valu-able to him, and to do it with speed and assurance. These chapterswill present him with tests that should give him this assurance.

There are about seventy metals known to science (the numberis uncertain because some are on the borderline between metaland non-metal), and of this number all except gold and copper aredescribed as white. When the student contemplates all the possi-bilities of composition and value that are presented by the words"a white metal" he must realize that the task calls for care, knowl-edge, and patience.

Fortunately for our purpose, most of the seventy-odd whitemetals are quite unsuited to jewelry making. Thus mercury isliquid at ordinary temperatures; tin is much too soft; potassiumreacts violently with plain cold water; radium gives off rays thatdestroy the flesh; and so on.

Our attention therefore will be placed primarily upon thosewhite metals that are precious, and upon those that are associatedwith them, or are apt to be confused with them.

THE MAGNET AS A DETECTIVE

Gold buyers often use a magnet to locate such things as steelsprings in bracelets. If a piece of metal is strongly attracted to amagnet it is probably iron or steel. However, certain nickel andcobalt alloys and some kinds of white gold also respond to the mag-net, which therefore should not be relied upon too implicitly, es-

pecially as some of the stainless steels are attracted only feebly ornot at all.

Other metals besides iron respond tothe magnet; some stainless steels do not.

THE FLAME TEST

If you can turn the flame of an air-gas or oxygen-gas blowpipeon a piece of suspected metal, you can, within a few seconds, ob-tain an excellent idea of its nature. Nickel, chromium, brass, andmost other base metals promptly turn black. Most base metalswill melt, forming oxides of characteristic color and form. Whitegold alloys will melt promptly in the oxy-gas flame; more slowly inair-gas. Or, if the flame is removed before actual melting occurs, adefinite darkening is visible. This is also true of sterling silver.

Fine silver when molten absorbs oxygen, and on cooling expellsit with violent spitting and "crabbing". This tendency is less con-spicuous with sterling and coin silver.

Stainless steel soon shows a darkening; if heated further it willignite and burn with a hissing and sparkling flame; the final resultwill be a shapeless lump of black oxides.

Tungsten, tantalum, and molybdenum change color at low tem-peratures, and soon begin to burn in the oxy-gas flame, though theywill not become actually molten.

The response of platinum and its high grade alloys to a flameis highly characteristic. (By high grade alloys we mean iridio-platinum, or others in which only precious metals are present.)Suppose you bring the metal to a brilliant red heat, then removethe flame. There will be no darkening whatever. Heat it still fur-ther using an oxy-gas flame, and melt it; it melts smoothly andcleanly, without forming any oxide or crust. When the buttoncools, it will be white and smooth. Base metals, treated in thatway, become a mass of clinkered oxides.

Palladium and alloys rich in palladium show colored oxides atabout 4000 C, but when heated further these disappear, and ifthe metal is cooled quickly they will not have time to form againand the cooled button will be free from tarnish.

Molten palladium absorbs very large volumes of gases, and ifthe flame is removed suddenly the gases are expelled violently. Thebutton that remains will be distorted and honeycombed withbubbles.

Low grade platinum alloys when heated strongly will darken,in proportion to the base metal present.

Fine gold, heated to redness, will cool without changing color.But if even small amounts of base metal are present, the surfaceafter cooling will show a film of oxide.

The oxy-gas flame, if properly handled, is thus one of the mostilluminating of all quick tests, and the air-gas flame is almost asuseful. This test will be discussed again in Chapter IV, and achart showing the responses of several metals to the oxygen flame isgiven in the Appendix.

SPECIFIC GRAVITY

In general the precious metals are heavier than base metals, andthe experienced worker can obtain a hint as to the value of anarticle merely by "hefting" it in his hand. This ratio between thebulk and the weight of a substance, called its density or specificgravity, is often helpful in identification. The student soon ob-serves that platinum and its high grade alloys are somewhatheavier than the white golds; while steel, nickel, silver, and mostof the base metals are so much lighter than platinum that thereis small excuse for a mistake.

Tungsten and tantalum are two base metals of very high specificgravity, comparable with that of platinum. However their leadencolor, and the fact that they ignite under the oxy-gas flame andform colored oxides, reduce the chances of confusion.

This method of identification, which has both its advantagesand its limitations, will be discussed again in Section C of ChapterIV, and in the Appendix.

How SILVER REACTS

As in Chapter I, the first step is to provide yourself with severalarticles of whose composition you are sure, then apply to them thevarious tests, in turn, and observe the results. Obtain a piece ofgood quality sterling silver, something made recently and stamped

by a reputable manufacturer; a silver coin; perhaps a bit of somelower-grade silver alloy; and some stuff that you know to be silver-plated.

First remove any surface coat, such as lacquer, and to each ar-ticle apply a drop of nitric acid. Let it remain for thirty secondsor so, then rinse it off and see if the surface of the metal were at-tacked. You will find that nitric acid reacts with silver, even thehighest grade, turning dark and making a gray spot on the metal.

Fine silver, when dissolved in nitric acid, gives a colorless solu-tion that darkens after exposure to light. Sterling silver and coinsilver show some green color, the green being due to the copperwith which they are alloyed.

To confirm silver, place a fresh drop of nitric acid on a cleansurface, let it react for a half minute, then with the point of a pen-knife drop in a single small grain of table salt. A white substancewill appear—silver chloride—of a cheesy consistency. This is char-acteristic of silver. Instead of the grain of salt you could use a tinydrop of dilute hydrochloric acid.

In effect this is almost the same as applying a drop of aqua regia.We think of aqua regia as a powerful solvent since it will dissolvegold. However, it is surprisingly slow to attack silver. Make thetest and see; note that the nitric acid in it will eat into the surface alittle, but very soon the white cheesy stuff forms, and protects themetal from further attack. Wash the metal and you will find thata whitish spot remains, difficult to remove.

This will help to explain why green gold, which contains muchsilver, responds more slowly to aqua regia than does yellow gold

of the same karat. Some of the high-karat green golds are almostinsoluble, even in hot aqua regia.

Here is another way to establish silver: In another bottle mixup nitric acid and a few crystals of potassium dichromate. Placea drop of this solution on the suspected article (after getting ridof lacquer, etc.) and note the color effect. Silver will show a verystrong, definite red, through the formation of silver dichromate.

SlLVERPLATED GOODS

The recognition of silverplated ware is usually easy. File a deepnotch and apply nitric acid to the cut, and note the difference inappearance and behavior of the silver surface and the base-metaltains no silver at all. Sometimes a brass core is found. Both ofthese core materials react quickly to nitric acid, causing it to bub-ble and turn a deep green.core. The favorite core material is a copper-nickel-zinc alloywhich is called "nickel silver" or "German silver/' but which con-

Ordinary silverplated ware is of such small value that refinersand gold buyers normally refuse to buy it, so it is important to beable to recognize it every time.

GOLD-ON-STERLING

In Chapter I we mentioned "gold" jewelry which was found toconsist of a sterling silver core to which a thin surface layer ofgold has been applied. The wearer may think of such jewelry asgold, but to the buyer it is silver. At present silver prices it is not to

Thin sheets of karat gold are welded to one or more surfaces of a thickbillet of less expensive metal—usually brass or a nickel alloy, sometimessterling silver—and the whole is then rolled very thin. The resulting thinsheet is used in making gold filled or rolled gold plate jewelry. In order tomeet U. S. standards the gold layer must be of at least 10-k quality. If theweight of the karat gold is more than 1/20 of the total weight, the jewelrymay be stamped "gold filled" The term "rolled gold plate" is used when

the gold layer is thinner.

be ignored, and sometimes there is enough gold present to add alittle to the buyer's price.

This combination is normally recognized in the preliminarytests involving nitric acid and a deeply-filed notch. Fresh, well-made goods present a handsome gold-like appearance, but if thegold film is thin, the silver soon tarnishes underneath the gold.

This combination attained special vogue during World War IIat the time when silver and fine gold were available, while copperand nickel—the metals so generally used in the cores of inexpensivejewelry—were subject to wartime restrictions. The fact that silverresponds only feebly to aqua regia has led some careless buyers tomisjudge the value of this combination, to their loss. Fortunatelyfor them, it is apt to be clearly stamped "Sterling." Sometimesthe outer layer of gold is of sufficient thickness and quality to classthe goods as "rolled gold" or "gold filled"; but these goods aregenerally stamped with a quality mark; e.g., "Rolled Gold Plate onSterling" or "Sterling -f- 1/20— 12K."

THE VARIOUS SILVER ALLOYS

Pure unalloyed silver, called "fine silver," is so soft that it hasfew practical applications. The most important alloy is sterlingsilver, which contains 925/ioooths fine silver, the remainder us-ually being copper. The word "sterling" goes back to the twelfthcentury; it seems that five towns in eastern Germany were bandedtogether in the so-called Hanseatic League; they were free citiesand maintained their own currency. The British soon learnedthat their coins, called the coins of the Easterlings, were depend-able; hence the term "sterling" as a stamp of quality.

Coins of the United States of America are 900/ioooths silver, theremainder being copper. Much jewelry and tableware used to bemade of this alloy, and may be stamped "Coin" or "Coin silver."

Alloys of lower silver content are often encountered, not onlyin the coinage of several foreign countries, but also in articles ofcommerce, but the designation "silver" cannot now be used legallyin connection with them in the United States. Imported goodsmay be encountered, stamped "Silver," which on assay may proveto be of very poor quality indeed.

It is sometimes desirable to make simple tests to distinguish be-

tween sterling, coin and lower grade silver alloys, but most ob-servers have found that it cannot be done with the same assuranceand satisfaction as with the gold alloys. Sterling silver and coinsilver differ by only 25 parts per 1000, or 2]/2 percent, and when werecall that both the silver and the copper are soluble in nitric acid,we can see why the acid test has its limitations. However, by hav-ing both surfaces clean and smooth, and by applying equalamounts of acid to both surfaces and exposing both together tothe light for the same length of time, and noting the color changes,the difference is detectable.

Silver of lower grade, if alloyed with copper, can easily be dis-tinguished from sterling silver in the same way. Unfortunately,these lower grade silvers may contain a variety of alloying elements—more or less nickel, or zinc, or cadmium—to fit them for differentpurposes, and unless you have some knowledge of the alloying ele-ments, these simple spot tests can be misleading, and experiencedworkers advise against their use.

SILVER SOLDERS

Silver solders, also called silver brazing alloys, are of manyformulas, containing from five percent to about eighty percentsilver, the balance being copper and zinc and perhaps some cad-mium. Large amounts of these alloys have been consumed inrecent years, in dozens of applications, not only in the manufac-ture of jewelry, but also in such jobs as the assembling of incendi-ary bombs, the repair of ice-cream freezers, the construction ofequipment for the chemical industries, and many others. Whilenot of high intrinsic value, these silver brazing alloys should notbe ignored by the metal buyer, especially as they may often befound in large quantities.

SOME WHITE BASE METALS

Many base metals are attacked and dissolved by nitric acid, butby no means all. Obtain scraps of various metals, such as lead,tin, pewter, Britannia metal, tungsten, stainless steel, aluminum,chromium-plated and nickel-plated ware, and so on. Clean themwell to remove any surface grease or lacquer, then touch each witha drop of nitric acid. Let it act for a half-minute or so, while you

observe any color changes, then wash well and notice if the surfacewere etched or spotted. To describe all the effects fully wouldtake more space than is here available; moreover, a few minutesspent at such tests will teach you more than hundreds of words. Sowe repeat: practice with pieces of metal of whose nature you aresure, exposing them to various tests and comparing results.

For instance, we suggest that you try the dichromate mixturementioned above, on other white metals beside silver. Lead showsa yellow color; Britannia metal turns dark. Platinum is not affectedin the least, nor is high-grade white gold, but palladium will bedarkened and will show a spot.

NICKEL-SILVER

The terms "nickel-silver" and "German silver" are applied toan important series of white alloys in which copper, nickel andzinc are the principal components. Both terms are highly mislead-ing, since no silver at all is present, and many other names havebeen suggested, including "nickel-brass" and synthetic words like"Cunizin" and "Nicuzin," none of which have received generalfavor.

Tableware and hollow-ware made of nickel-silver and electro-plated with silver, nickel, or chromium, have been made in enor-mous quantities. Rolled and filled gold jewelry, especially thatwhose outer layer is white gold, is generally made on a nickel-silverbase; and there are dozens of other applications.

Accordingly it is important that the gold buyer be able to recog-nize these nickel-silver alloys wherever found. They are attackedvigorously by nitric acid, showing a strong green color because ofthe copper and nickel content. When heated strongly theydarken; under the oxygen flame they ignite and burn to a blackclinker, meanwhile conferring a green color to the flame.

STAINLESS STEEL

This handsome but inexpensive alloy, stainless steel, has hadquite a vogue for sports jewelry, men's belt buckles, wrist watches,etc. In appearance it resembles white gold or platinum. Oddlyenough it is not readily attacked by nitric acid nor by aqua regia,

and for that reason it has occasionally deceived unwary appraisers.As we have indicated, some kinds are attracted to the magnet, someare not.

It is considerably lighter in weight than either white gold orplatinum, and most jewelers will at once notice this lack of "heft".As we mentioned above, it darkens under the oxy-gas flame, thenignites and burns to a dark clinker.

But if you are in doubt about any article of white color andnoticeable hardness, which resists the action of nitric acid and ofaqua regia, pause a moment and then test it with plain hydro-chloric acid.

If possible, heat either the article or the acid somewhat; hydro-chloric acid attacks the stainless steels promptly, making a definitespot or dissolving the streak in a short time. Sulphuric acid also at-tacks stainless steel; so does a solution of ferric chloride. None ofthese affects white gold or platinum.

RESISTANCE ALLOYS

There are dozens of more-or-less white alloys on the market,which though not stainless steels by definition (since they containlittle or no iron) are often confused with them. We refer to thoseheat- and corrosion-resisting alloys of which Stellite, Nichromeand Illium are only three examples of a long list. Chromium,cobalt, nickel, tungsten, silicon, manganese and other elementsmay be present, and the number of formulas is legion. Occasion-ally such alloys present an appearance that might confuse themetal buyer, and many of them resist nitric acid surprisingly well.But mostly they are lighter in weight than platinum or white gold,and their crystalline structure and their "feel" under the file givesufficient warning. Their melting points are high, but under thestrong heat of the oxy-gas flame they will ignite and burn, after themanner of other base metals.

SOME LESS COMMON METALS

Tungsten, tantalum and molybdenum are three of the semi-raremetals that have found growing commercial importance during

recent years. In color they are somewhat dark, and are tough,heavy, strong and hard. Their carbides are extremely hard, andare compacted and sintered into points or blades for drills, cuttingtools and the like, for which purpose they rival the diamond.

These metals all possess remarkable resistance to nitric acid,aqua regia, and most other reagents, and accordingly have sometimes been confused with the platinum metals. But above redheat they all oxidize readily, and under the oxy-gas flame they ig-nite and burn to form colored oxides.

CONTACT POINTS

Electrical contact points must have high heat and electricalconductivity, hardness, strength, and resistance to corrosion atthe high temperatures of the electric arc. Many metals and alloysare being used in their manufacture—silver, copper, platinum-group metals, tungsten, tungsten carbide, cobalt, and others. Some-times a point consists of two alloys welded together, the combina-tion then being brazed or welded to the device of which it is apart, and many of the alloys involved are quite complex.

Old contact points can be quite a problem to the metal buyer.Knowing that much platinum and iridium go into this market, heis tempted to buy the things, even after experience has taught himthat he is more apt to lose than to profit when handling them.The task of appraising them and recovering the precious metals,if any, is difficult, and many professional refiners refuse to buythem. Accordingly the beginner is advised to approach thismarket with caution.

CHROMIUM PLATE

Chromium is a hard white metal, unusually resistant to mostcorrosive agents. Chromium plate, when properly applied, is ahandsome finish and sometimes is used on cheap white goldjewelry, as well as on many base metal articles.

It resists nitric acid, and therefore is sometimes mistaken forwhite gold or platinum. However, it is attacked readily by hydro-chloric acid, and by sulphuric acid. When heated under the air-gas or oxy-gas flame, it blackens promptly.

RHODIUM PLATE

Rhodium plate is also deceptive. Rhodium is a metal closelyrelated to platinum, costing more per ounce than platinum itself.It can be deposited electrolytically in a very thin layer, on silver orbase-metal articles, to give them a handsome appearance, free fromtarnish. Rhodium is not attacked by nitric acid, aqua regia, norany other single acid. It is fairly hard to the file—almost as hard aschromium plate. But the deposit is always so thin that a fewstrokes of the file will expose the metal below. For that reason itshould not cause any great confusion to the buyer of preciousmetals.

WHITE GOLDS

The tests described so far, when applied to most white golds, willbe suggestive, but not always conclusive. You may still be uncer-tain as to whether the unknown is white gold or a platinum metalalloy of some kind. We shall therefore return to the white goldsin a later chapter, with conclusive tests.

THE PLATINUM METALS

These metals and their alloys are so important, not only injewelry and dentistry but in many other applications, that an en-tire chapter will be given over to them.

For the moment we shall content ourselves with rememberingthe facts we have recently noted: that platinum is not attacked bynitric acid nor by hydrochloric acid; that its melting point is veryhigh; that it melts cleanly under the oxy-gas flame and coolsagain without the formation of visible oxide; and that it is notice-ably heavier than most other white metals.

Palladium is the one metal of the platinum group that is at-tacked by nitric acid. It dissolves promptly to give a deep brownsolution. It is much lighter in weight than platinum. Palladiumelectroplate is sometimes used to give a handsome non-tarnishingfinish to jewelry or scientific instruments. Alloys in which goldand palladium are the main constituents are important in dentis-try, also they form one kind of white gold. All of these, and others,will be discussed more fully in Chapter IV.

CHAPTER III

The Quality Stamp—"Let the Buyer Beware!"Since gold and silver have been used in coinage for many cen-

turies, it is natural that their stamping or marking should be reg-ulated by law. Such laws are not only a protection to the pur-chaser, but are of equal value to the manufacturers because theysustain public confidence in the industry. Regulations for theplatinum metals are of more recent date.

Everyone who handles precious metal articles should under-stand these laws thoroughly. Thus the manufacturer must keephis alloys high enough to meet the law, but not so unduly high asto jeopardize his profits. The retail jeweler, who is equally liablebefore the law, does well to check the goods he sells and to giveattention to the reputation of the manufacturers from whom hebuys. The metal buyer, in his turn, has good reasons for observ-ing and interpreting the various stamps. For example, if an ar-ticle is marked "10-k," he need not waste time testing it againstthe 12-k needle. Also, he should familiarize himself with thetrademarks of the various manufacturers, and observe which, ifany, are associated with sub-standard goods. Finally, all groupsmust understand the meaning of "tolerance" in marking, whichwill be explained shortly.

BRITISH HALL MARKS

The marking of gold jewelry began in England in the four-teenth century. The Goldsmiths' Company, incorporated in 1327,and certain other Guilds, found it necessary to organize for theprotection of their craft and of the public against fraud. Theyhad, among other functions, that of testing gold and silver articlesat their several Halls. A small sample was cut from each pieceand assayed, and the article then received four or more stamps,including the quality mark, a town mark, a date letter (changedeach year) and a maker's mark. Various symbols were used, such

as a leopard's head, a crown, a lion, and the like. Goods madebetween 1784 and 1890 also carried a duty mark indicating that acertain tax had been paid. Stamping was not compulsory, andsmall articles were not always marked. It should be noted that

13 CARAT GOLD.

9 CARAT GOLD.

STANDARD SILVER.

Some British Hall marks. These were usedby the Birmingham Assay Office.

these marks were impressed not by the maker, as in the UnitedStates of America, but by the Guild Halls, after assay. Hall mark-ing has been the subject of a considerable literature, which is wellworth the study of the antiquarian and historian.

AMERICAN LAWS AND STANDARDS

In this country the manufacturer himself, subject to law, is per-mitted to affix quality marks and trademarks to his goods. TheUnited States National Stamping Law, covering falsely or spur-iously stamped articles made of gold or silver or their alloys, wasenacted June 13, 1906. The text may be found in almost any lawlibrary or big public library. (Ask for Rev. Stat. U. S., vol. 34, pt.1, p. 260, 59th Cong., 1st Sess., Public Law 226.)

Handy and Harman, silver dealers at 82 Fulton Street, NewYork, sell a reference book called Handy Book for Manufacturers,which contains, among other useful facts, the full text of the lawjust mentioned, as well as summaries of the laws affecting plati-

num, of the several Commercial Standards which now have theeffect of law, and of the Canadian law applying to the marking ofprecious metals. Another most useful volume is Trademarks ofJewelry and Kindred Trades, published by the Jewelers' Circular-

Some American stamps. They consist of the quality stampand the maker's registered trademark.

Keystone, 100 East 42nd Street, New York. This book illustratesseveral hundred trademarks, and in addition summarizes thestamping laws and explains their application.

The manner in which the various silver alloys may be stampedhas already been discussed in this book—see Chapter II.

"TOLERANCE"

Our lawmakers have assumed that jewelers and silversmiths aresubject to human error, so they allow a "tolerance" between thequality indicated by the stamp and the actual quality as deter-mined by an assay. The law also allows for solder, and requiresthat the article, solder and all, must approach within a certainpercentage of the stamp. Thus the law of June 13, 1906, as sum-marized in the Handy Book, provides that:

"If an article is made of gold and is stamped gold, it must also bear aquality mark such as *io karat' (10-K), '14 karat' (14-K).

"If an article of gold is given a quality mark, the fineness by assay mustnot be lower than:—

Watch Cases and Flatware .003 less than stamped quality.Other articles, not including solder 0208 (i/2 karat) less than the

stamped quality."However, the assay of a complete article, including solder, must not be

more than .0417 (1 karat) under the stamped fineness per karat."For example, the gold in a 14-karat watch case, free from solder, must

be at least .5803 by assay. The entire case, including solder, must assay atleast .547 (13 karat). A gold ring, not soldered, stamped '14-K' must assayat least .5625 (13I/2 karat). The gold in a brooch stamped '10-K' must as-say at least .3958 (gi/2 karat) and the entire brooch, solder and all, mustassay at least .3750 (9 karat).

"The silver in any article stamped 'Sterling Silver' should assay .925,and the silver in an article marked 'Coin Silver' should assay .900. Thesilver in an article, not including solder, must not be less than this bymore than .004. For example, an article marked 'Sterling Silver,' free fromsolder, must assay at least .921.

"Soldered parts must not reduce the assay of the entire article, includ-ing solder, by more than .010 under the standard assays of .925 and .900,respectively, for sterling silver and coin silver. For example, an articlemarked sterling silver when melted, including solder, must assay at least

Most manufacturers make their goods as close to the limit oftolerance as they dare. Many of them, either wittingly or unwit-tingly, go below this tolerance. The buyer must keep this pos-sibility in mind when he is calculating the value of a precious metalarticle.

LAWS FOR STAMPING PLATINUM

For some years after the introduction of platinum as a jewelrymetal there was confusion regarding its marking, and much mis-branding, adulteration and fraud took place. Three of the Statesin which considerable platinum jewelry was manufactured—NewJersey, New York, and Illinois—passed laws regulating the stamp-ing of platinum and its alloys. And finally, on June 20, 1938, theNational Bureau of Standards made effective a series of regula-tions, based on these State laws, that cover the entire nation. Thefull text of the New York State law will be found in the HandyBook. Copies of the new National Standard, known as CommercialStandard 66-38, may be obtained from the Superintendent of Doc-uments, Washington, D. C, for 5c. Briefly its main provisionsare as follows:

Articles may be stamped "platinum" or "plat," provided all parts ofthe article purported to be of platinum shall constitue at least 985/1000parts platinum. If platinum assaying 985/1000 parts pure has been com-bined with gold the article must be stamped with the karat mark indicat-ing the fineness of the gold in conjunction with the word or abbreviationof platinum, as "14K & Plat." When platinum is alloyed with iridium,palladium, ruthenium or osminum, these articles must be marked infractions designating the content of these metals. Merchandise bearingquality marks must also be stamped with a registered trade mark.

Since the rules regarding the stamping of platinum alloys arenew, a great deal of platinum jewelry now in use was made beforethese controls were drafted. Accordingly some of the marks onplatinum jewelry are misleading now. For years palladium wasmore expensive than platinum; therefore it was accepted practiceto use palladium with platinum, without mentioning the fact.Later the price of palladium fell below that of platinum, and ametal that had once enhanced the value of an article became acheapener. This situation is only one of the reasons why the pur-chaser should test platinum articles with extra care.

OTHER COMMERCIAL STANDARDS

The National Bureau of Standards, in co-operation with theprecious metal industries, has formulated several other "Com-mercial Standards" that may be of interest. These Standards havetheir origin in the Bureau, rather than in the legislative halls,and are a crystallization of trade practices. They are subject toamendment when an interested industry feels that changes are ad-visable, and they are enforced by the Federal Trade Commission.Copies may be obtained from the Superintendent of Documents,Government Printing Office, Washington, D. C, at five cents each.Other standards may possibly be adopted in the future. The fol-lowing are now effective:

Marking articles made of silver in combination with gold—Com-mercial Standard 51-35.

Marking articles made of karat gold—CS 67-38.Marking of gold filled and rolled gold plate articles other than

watchcases—CS 47-34, with amendments of February 25, 1939. Bui-

letin TS-1942, of July, 1933, defines the terms "Gold filled" and"Rolled gold plate."

Marking of jewelry and novelties of silver—CS 118-44.

ENFORCEMENT

While the marking of precious metals has, as we see, been sub-ject to law for centuries, obedience to these laws is not yet perfect.But the fight for honesty in marking and in advertising is beingcarried on actively by a number of organizations, some of themmaintained directly by the precious metal industries. The readerwho finds instances of fraud or misrepresentation would reportthem at once to the Better Business Bureau of his city; or, he or hisjeweler should communicate with the Jewelers Vigilance Commit-tee, Inc., New York 19, N. Y. These groups, in co-operation withthe Federal Trade Commission and the National Bureau of Stand-ards, have accomplished much, not only in the enforcement ofpenal laws, but also in obtaining official condemnation of variousborderline cases. Also the American Gem Society of Los Angeles,through its members, has done a great deal toward clarifying theadvertising and labeling of diamonds and other gem stones.

STANDARDS IN FOREIGN COUNTRIES

Each nation has its own standards, not only for the alloys usedin coinage, but also for silverware and jewelry. In Chapter II weobserved that the word "silver" on a piece of jewelry does not meanthe same thing in all lands. To give the details of all these varyingstandards would not be profitable here, inasmuch as the buyerrarely is sure of the origin of the old metal he buys. The wise prac-tice is to confirm all stamps by one or another of the methods de-scribed in these chapters.

"LET THE BUYER BEWARE!"

If every article made of precious metal was truthfully stamped,there would be little need for a book like this. But many articlesare never marked at all—dentures and chemical ware, for example.And the antiquarian handles articles made before the present lawswere framed. An article can be truthfully marked when made,

then, perhaps because its thin outer layer is worn off, or becausesome repair job added considerable solder or even an additionalpart of a different composition, the old mark may have becomemisleading. Finally there is always the possibility of fraud. Thusit is clear that the buyer of old precious metals must indeed bewary. One well-known buyer says, "Never believe a karat markunless it is accompanied by a reputable trademark, and sometimesnot even then." If there is no trademark, the stamp may well bequite meaningless.

Chains and mesh are probably the worst offenders. It is recog-nized that considerable solder is needed in making some kinds ofchains, and the wise buyer will assume that even more than that ispresent. Links that test say 12-k on the stone, when melted downand assayed may turn out to be 10-k or less; chains that test 10-kon the stone may assay 8-k. And so on.

SOME PRECAUTIONS

If an article consists of more than one part, like the old-fashionedwatchcase with front, back, bezel and bow, test each piece sep-arately, as those less exposed may be of lower value. Lockets andbig cuff links sometimes are re-inforced by a base-metal disk inside.Examine the pin and safety catch on brooches. Do not hesitate tofile deep notches, maybe two or three, on different surfaces of eachpiece. Remember that an old article may have been repaired,with the addition of much solder or even a new low-karat segment.

Articles such as candlesticks are often made of a hollow metalshell which is filled or loaded, sometimes with pitch, sometimes

with lead which has been melted and poured in. Sometimes thebase alone is loaded. This same scheme has been used withheavy link bracelets, etc., and has occasionally deceived the in-experienced observer.

Rolled or filled gold requires special care. It consists largely ofbase metal such as brass, with a thin layer of karat gold on theoutside. Usually this outer layer is 10-k or 12-k. You may find astamp reading "1/10 12-k." Analyze this stamp and you willrealize that this article when new assayed only one-twentieth finegold, as the 12-karat alloy is only half fine gold, and the karat goldshell is only one tenth of the total weight of the article. Afteryears of usage the outer gold layer, originally very thin, may beworn down to almost nothing. Therefore, when estimating itsvalue, "let the buyer beware." Some professional gold buyers re-fuse to handle this material.

ANTIQUES

Very old gold jewelry is sometimes worth more than you wouldthink. Years ago when platinum was cheaper than gold, it wassometimes used as an alloy. It cheapened and stiffened the gold,without increasing its tendency to tarnish, and in rare cases wasused in sufficient amount to increase the value of the article. Onthe other hand, much old jewelry is dishonestly marked, and some-times you will find that an antique with a handsome exterior isnothing but soft solder inside.

FRAUD

Deliberate fraud occurs too often to be ignored. The Jewelers'Circular-Keystone, in its issue of September, 1943, reports one in-stance. A customer complained that a certain ring, stamped andsold as 14-k gold, blackened his finger. The retailer tested ithastily (by rubbing an edge on the stone and testing the streak)and it seemed to be a full 14-k. But further examination dis-closed that about nine tenths of the ring was silver, lightly gilded.Thin circles of 14-k gold wire had been soldered to the top and bot-tom edges of a heavy silver ring, so that if a touchstone test weremade in haste, only gold would rub off. The moral of this is: file

a deep notch if possible, and test more than one surface. Inci-dentally, the buyer might have been warned by the fact that whilethis ring bore a karat stamp, there was no maker's trademark—al-ways a suspicious circumstance.

A poorly disguised fraud. Circles of thin gold wire were soldered to theedges of a heavy silver ring, and the combination was gold-plated. Thequality stamp was not accompanied by a trademark. Part of the silver ring

and part of one gold circle have been cut away.

DENTAL ALLOYS

Metals that have been used in dentistry carry no stamp, andtheir purity and suitability depend upon the integrity and knowl-edge of the dental technician. Much dental gold is of high qual-ity, especially inlays and crowns, but in the construction of a den-ture it is often necessary to use considerable solder, which may be16-k, 14-k, or even lower. Parts of metal that are covered by vul-canite or porcelain may be of low grade gold or even of base metal,and sometimes rivets of copper or silver are used, then coveredover with gold solder.

Old fashioned false teeth were, in many cases, provided with twosmall pins of high-grade iridio-platinum. Much of the work donetoday, while more satisfactory to the patient, may contain noprecious metal at all, so each job must be considered individually.

SCIENTIFIC APPARATUS

Enormous amounts of precious metals have been made up intoinstruments and equipment for the various scientific industriesand professions. The laws applying to jewelry apply equally well

to these instruments, and quality stamps and makers' trademarksshould always be looked for. In other chapters we learn that inthese fields the precious metals may be alloyed with or combinedwith each other, or with the base metals, in such a profusion offorms that the beginner may well be discouraged. However, noother field is potentially more profitable to the buyer of metals.

TREASURE HUNTING IS STILL FASCINATINGThese paragraphs may have suggested that this business of buy-

ing and selling old precious metals may be as interesting as it isprofitable. To find value in a piece of unattractive, unwantedmetal brings a thrill of satisfaction over and above the mere gratifi-cation of the profit motive. To solve the question of its worthmay be as full of unexpected twists as any other puzzle. For in-stance, we once had occasion to buy a heavy old-fashioned watch-chain. Its appraisal seemed to be as simple a task as could befound. We exposed the metal to the oxygen flame; all the linksglowed, but three of them glowed with a difference. On closerexamination we found that those three links were silver—carvedexactly like the others—apparently the result of some old repairjob, long since forgotten. On another occasion one section of adiscarded penholder, when scraped clean of encrusted ink, turnedout to be 18-k gold. . . . Incidents like these help to make thiswork a constant adventure.

CHAPTER IV

The Platinum-Group Metals and the White GoldsSECTION A. NEW METALS; OLD TESTS

WHEN platinum first came into vogue, it was natural to applyto it the same tests that we use on gold and silver. As we have

learned, the old acid and flame tests, described in Chapters I andII, are extremely useful, but they do not always tell the observer asmuch as he wants to know. Accordingly it is our purpose now toexpand these tests, then later to add some new ones, to permit therecognition of many of the alloys of the platinum group that arenow in use in the arts and industries.

It is only fair to point out while some of these white metals arepromptly and easily identified, this is not true of all of them. How-ever, all these tests are well within the powers of the layman whowill follow instructions, who is willing to obtain indubitablesamples of the various metals, and who will practise with thesesamples until he learns their characteristics.

THE SIX SISTER METALS

Platinum, palladium, and iridium are the more plentiful mem-bers of the platinum group, and the ones of greatest general inter-est. The other three, osmium, rhodium, and ruthenium, are muchrarer but are finding increased usefulness as time goes on.

These six metals share certain characteristics, notably rarity,white color, density, resistance to corrosion, high melting points,and many chemical peculiarities; but, like human sisters, each hasan individuality of its own.

Many combinations of two or more of these six, with or withoutadditional metals from other groups, have found employment injewelry, in many industries, and in the sciences. To explore allsuch combinations would require much more space than is hereavailable. These chapters, therefore, will concern themselvesmainly with those alloys that are of interest to the jeweler and the

old jewelry buyer. These include the two or three kinds of "hard"platinum that form the foundation of the platinum jewelry in-dustry; those alloys of palladium that have found favor in jewelry,including the white golds, and a few of the alloys in which basemetals are present by accident or design. Because of their resem-blance to the alloys used in jewelry, a number of dental alloys willalso be included.

WHAT WARS DO TO JEWELRY METALS

When platinum jewelry first came into fashion, early in thiscentury, the alloys generally used were the simple iridio-plati-nums. (Pure platinum is almost as soft as fine gold, and must behardened and stiffened for most purposes. The addition of 5percent to 10 percent iridium gives an ideal alloy for jewelry pur-poses.) Careful assay of jewelry made at that time may show otherelements, but these probably got there by accident because knowl-edge of how to purify these metals was then far from complete.

World War I clamped an interesting economic pincer on plati-num. Russia was the main source of supply, and it was cut off bywar. At the same time demands increased hugely, both becauseplatinum is used in making chemicals for the munitions industries,and also because the public wanted jewelry made of platinum anddid not care how much it cost. Accordingly prices skyrocketed.

This situation so stimulated the ingenuity of metal workers thatmany substitutes and new alloys were devised. Some of these havefound honored places in the world of metals, for example, someof the palladium and ruthenium alloys. Some others, in whichnickel and other base metals were used, had poor working quali-ties, and in addition were economically unsound since their com-plexity caused enough trouble in refining and remelting the scrapto counterbalance the original saving.

The fact that we then had no regulations to cover the platinumgroup served to increase the confusion and to encourage fraud.

One of the by-products of the great demand for white jewelrywas white gold. The first white golds were gold-palladium alloys,followed shortly by a variety of alloys in which nickel served aswhitener. The fact that these alloys came under the gold stamping

laws tended to reassure the careful buyer, and doubtless con-tributed to their popularity.

In England a considerable quantity of palladium jewelry wasmade during World War I, even though at that time its price washigher than that of platinum.

World War II, in its turn, placed restrictions upon most of ourmetals, and again challenged the ingenuity of the precious metalmetallurgist. One expedient, rolled gold on a silver base, wasmentioned in Chapter II. During the long Armistice, our chem-ists and refiners had learned much about the properties and puri-fication of the six members of the platinum group, and supplies ofmost of them had increased considerably. As a result, alloys andcombinations that had been standing unnoticed in the laboratorywere escorted forth to make their debut upon the stage of fashion.

Thus, when iridium went to war, ruthenium came forward,and the useful ruthenio-platinum was introduced to the jewelryworld. In working qualities it so nearly resembles the classic iridio-platinum that its future as a jewelry alloy seems assured. How-ever, "Ruth-Plat," as it is designated by the commercial standardwhich by this time had been formulated for the platinum group,was in its turn a war casualty when platinum came under restric-tion. Rhodium also was called to the colors. Finally certainpalladium alloys in which ruthenium serves as hardener, receivedtheir opportunity, and "jewelry palladium" came into use.

When in our mind's eye we review this parade of alloys acrossthe stage of history, we realize that the task of identifying them hasbecome more and more complex. We see why the itinerant goldbuyer became confused and decided that it was better for him notto bother with the white metals at all. We see why identification,though more difficult, is far more interesting, and when properlycarried out is correspondingly more profitable. (Incidentally, thisreview brings the practical suggestion that a hint as to the compo-sition of a piece of "platinum" jewelry may sometimes be found inthe date at which it was made.)

SAMPLES NEEDED FOR TESTING

When we were examining silver and some other white metals inChapter II, we provided ourselves with samples of as many differ-

ent metals as possible. The serious student will now provide him-self with as many samples of platinum-group metals and their al-loys as possible. Sets of standard platinum needles, much like thestandard gold needles, are on the market, and are useful. Theseare brass points, tipped with bits of pure platinum, pure palla-dium, several of the platinum-palladium alloys and an iridio-platinum alloy.

Standard needles for testing platinum-group alloys.

In addition to these, however, or in place of them, you shouldobtain from a reputable source several sizable pieces of metal—apennyweight or so of each will be enough for the careful worker—which you will feel free to heat to redness, and from which you cancut off portions to be dissolved in acids, and to which you can applythe various reagents. By all means have pieces of pure platinum,pure palladium, and fine gold. If you plan to distinguish betweeniridio-platinum and ruthenio-platinum, buy samples of both al-loys. The highest grade white golds, which consist of about 85per cent gold with 15 per cent palladium, more or less, are usuallythought of as gold alloys, though they can with equal propriety becalled palladium alloys. It is well to have samples of one or twoof these. The more samples you have to compare, the greater willbe your skill and assurance in identifying unknowns.

Mark each sample carefully by stamping or engraving on itsome symbol or number. One plan is to have each piece a differentshape—square, or oblong, or triangular, or the like—and to makecareful record of the composition of each piece.

THE ROUTINE OF TESTING

Let us assume that we have some white metal articles and wish topick out those made of precious metals and to determine as muchas we can of their composition.

First we employ the tests described in Chapter II. If the studentis not already familiar with these, he should read that chapteragain, noticing carefully the references to the platinum metals andthe white golds. Thus we use the magnet; we use the air-gas or theoxy-gas flame; we observe the specific gravity or "heft" of the ar-ticles; we file deep grooves and apply nitric acid: sometimes we ap-ply plain hydrochloric acid, or plain sulphuric acid, or a grain oftable salt. Probably by this time we have separated out the basemetals and discarded them, and quite possibly we have formedexcellent guesses as to the composition of the more resistant arti-cles.

If in doubt, we subject our samples to the same tests, and observeresults.

THE AIR-GAS OR OXY-GAS FLAME

All manufacturing jewelers, all jewelers who do repair work,and all dental technicians, have air-gas or oxy-gas torches of onetype or another. Such a torch properly used is one of the best, aswell as one of the quickest devices for the identification of preciousmetals. As we have suggested in Chapter II, a few seconds spent inbringing a suspected metal to red heat may answer all your ques-tions. The flame will spot the base metal articles for you, and maygive you valuable clues to the composition of the precious metalarticles.

The use of oxygen from a tank, instead of compressed air, has be-come increasingly common not only for making platinum jewelry,where it is essential, but also for making gold or silver jewelry.For our purposes the oxy-gas flame is preferred. Oxy-acetyleneflames are almost as good, but are so hot that they must be usedwith caution.

We have learned in Chapter II that platinum and its preciousmetal alloys, if brought to white heat and then allowed to cool inair, will show no tarnish whatever, differing therein from mostwhite golds, from sterling silver, and from all the base metals. For

that reason the professional metal buyer normally makes thistest the first order of business. For that same reason the estab-lished jeweler or dental technician, who has a torch and knowshow to use it, is better equipped to buy old precious metals thanis the most energetic house-to-house buyer.

One kind of small oxygen-gas blow-pipe.

Much can be learned about a piece of metal by heating it to itsmelting point—by making it actually molten. For example, iridio-platinum is slower to melt than soft platinum; the more iridiumthe higher the melting point. If base metals are present, even insmall amount, the button that forms on cooling will show a dark-ened surface and probably will be brittle. An experienced meltercan identify the impurities by the stains that form on the crucible.

Palladium responds to the flame rather oddly. If you start withcold metal and heat it gradually, you will see films of peacock-colored oxides play across the surface when the metal reaches about4000 C. At about 8oo° C. these disappear, and if you quench thehot metal in water at the right moment, it will cool before theoxides have time to form again, and the button will be clean andwhite. The melting point of palladium, 15540 C, is higher thanthat of gold, lower than that of platinum. Molten palladium ab-sorbs large volumes of gas, and the button swells and puffs; thenwhen it solidifies again the gas is expelled with much spitting and"crabbing."

But it is not always possible or convenient to heat your unknown

metals to the molten stage. Sometimes, in fact, you will wish todamage their appearance as little as possible. That brings us tothe second section of this chapter, to a series of tests in which aminute quantity of the unknown metal is dissolved in a drop ofaqua regia, then treated with some chemical that will reveal itsnature.

SECTION B. NEW METALS; NEW TESTSIf the student has not already done so, he should at once assem-

ble his samples of platinum, platinum alloys, palladium alloys,white golds, and so on, and apply to them the traditional acid tests—first nitric acid, then aqua regia.

So, let us now with our samples of metals and alloys of knowncomposition, make metallic streaks in the cavities of the spot plate,rubbing hard with the hard metals, more gently with the soft ones.Next we shall treat the streaks with nitric acid, then with aquaregia. Following that, whenever such tests do not tell us all wewant to know, we shall add some new and additional chemicals,thus carrying out the new tests that have been developed in stepwith the development of these new alloys.

NITRIC ACID AND PALLADIUM

Palladium is the only member of the platinum group that dis-solves in nitric acid. Make a streak in a cavity of the spot plate,add a drop of nitric acid, and observe the deep brown color of thesolution.

Pure palladium is too soft for most commercial purposes. Alloysstiffened with a little ruthenium and rhodium have working qual-ities suitable for jewelry, and attained a mild vogue during thelong Armistice. When, during World War II, restrictions wereplaced on rhodium, platinum, and ruthenium, the so-called"jewelry palladium" came into quite general use. Several formulaswere used, in most of which ruthenium had the role of hardener(with or without the addition of other elements), and some hand-some palladium jewelry was made. In most of these alloys theproportion of palladium is so high that nitric acid attacks themat once, showing the brown color. Later in this chapter confirm-atory tests for palladium will be described.

The inclusion of even a little platinum in a palladium alloygreatly reduces its solubility in nitric acid. Thus the alloy 98%palladium with 2% platinum reacts on the stone like 14-k gold;and the alloy 90% palladium with 10% platinum resists the coldacid completely.

Clean the spot plate after each using, dissolving any stain withnitric acid or aqua regia, then rinsing well with plenty of water.

AQUA REGIA AND THE PLATINUM METALS

Again make streaks in the cavities of your spot plate, using yourplatinum-group metals and alloys, your samples of white golds anddental golds, and if possible including several samples of low-

grade platinum alloys—alloys containing copper or nickel or silver,with or without gold or palladium.

Mix up some fresh aqua regia. For this work a good mixture isone part nitric acid to four parts hydrochloric acid, and the bestcontainer is a dropping bottle. The sketch shows one type of drop-ping bottle. Notice the grooves on the stopper and in the neck ofthe bottle; when these coincide you can easily pour out one drop,or as many as you wish, without fumbling or waste.

One kind of dropping bottle.The stopper is grooved, andthere is a channel in the neck

of the bottle.

Never close tightly any bottle that contains aqua regia. Keepthe stopper turned so that the grooves coincide and the gases thatevolve may escape. If dropping bottles are unobtainable you canmanage with ordinary glass-stoppered bottles and a handful ofmedicine droppers or small glass rods; but the dropping bottlesare much the better arrangement.

Add about four drops of aqua regia to each metallic streak, andawait results. With some streaks the acid goes to work at once.With others the action is so slow that the hasty observer will con-clude that they are not dissolving at all. But sooner or later, de-pending upon the nature of the alloy and the temperature of theplate, the aqua regia will take on a deeper color and the metallicstreaks will disappear.

In a notebook write down the order in which the streaks are at-tacked.

To hasten matters, heat the plate until it is uncomfortably hotto the hand, possibly by placing it on steam pipes, or on an asbestospad resting on an electric hotplate; or grasp it with tongs and slipit into a pan of hot water.

We spoke just now of lower-grade platinum alloys—those con-taining base metals. Compared with iridio-platinum and ruth-enio-platinum, these may dissolve readily in aqua regia, thereforemay be confused with certain high-grade alloys in which palladiumor gold is present. On the other hand, low-grade alloys containingmuch silver may be as slow to react as the very valuable "hard"platinums. Thus we see that the mere rate of solution gives onlypartial information as to the value of an alloy; thus copper or pal-ladium hastens action, while silver, iridium, or ruthenium slows itdown, and observations based on speed alone can be quite mislead-ing.

This brings us, then, to the modern extensions of this method,whereby it is easy to detect palladium or gold (or both) in a plati-num alloy; also to detect platinum, palladium or nickel in a whitegold or dental alloy; and to distinguish between iridio-platinumand ruthenio-platinum. First we make a streak with our unknownmetal and dissolve it in aqua regia. Then we add certain chem-icals to the drop, and by noting the color changes we learn thecomposition of the unknown. That is the whole story in one par-agraph.

STANNOUS CHLORIDE TESTING SOLUTION

This solution, often called "Testing Solution A," is extremelyuseful. Rightly handled it reveals the presence of gold, silver,platinum, iridium and palladium in solution, and suggests theproportions in which they are present. It is easy to prepare andthe ingredients are inexpensive.

From your supply house purchase an ounce of stannous chloridecrystals, and an ounce or less of pure tin metal—mossy, granular, orfoil—but it must be pure tin. You will also need some hydro-chloric acid, and by far the best container to use is a droppingbottle, similar to that mentioned above. These quantities willprovide several hundred tests.

Make up only a little of Testing Solution A at a time, as it doesnot keep well. Take about a pennyweight or less of the stannous

chloride crystals (also called tin salts) in the dropping bottle, adda half pennyweight or so of tin metal, and fill the bottle three-fourths full of water. Tap water will do. Now add about 20 to30 drops of hydrochloric acid, more or less, to a 30 cc. bottle. Thisgives a milky liquid that is ready to use. The tin metal will dis-solve very slowly, and it serves to keep the solution in good condi-tion. Label the bottle "Testing Solution A."

As we said, Testing Solution A when properly used shows thepresence of precious metals in solution. In order to get acquaintedwith the color-changes involved, you should first make up somesolutions containing these precious metals. You should have asolution containing gold, one containing platinum, and other con-taining palladium. This method is so useful and fascinating thatmost users wind up with a whole series of standard solutions, soperhaps you might as well get a half-dozen dropping bottles in thefirst place.

STANDARD SOLUTIONS OF GOLD, PLATINUM, PALLADIUM

To make up a standard solution, simply dissolve a small pieceof metal in a little aqua regia, then add water. For instance, takeexactly a grain of pure platinum wire; dissolve it in a little aquaregia, using a small porcelain dish and heating gently until all themetal dissolves. Use as little aqua regia as will do the work. Washthe solution with water into a glass-stoppered two-ounce bottle,and fill the bottle up to the mark with water. Label this bottle"ONE GRAIN PLATINUM IN 2 FLUID OUNCES OF SOLUTION."

(When your only object is to become acquainted with the vari-ous solutions, it is not necessary to use exact measurements. Butlater on, when trying to approximate the amount of preciousmetal in a solution, it will be extremely helpful to have standardsolutions made up with a definite weight of precious metal in adefinite volume of liquid. Therefore it saves time to make upyour solutions in the beginning according to a definite plan.)

STANNOUS CHLORIDE TESTING SOLUTION WITH PLATINUM

Let us become acquainted with Testing Solution A. Take thespot plate and drop one drop of the standard platinum solutioninto a cavity. Notice the pale yellow color. Add a drop or more

of Testing Solution A. If properly prepared the two will react in-stantly to give a deep yellow or brown color. If too concentrated,the color will be almost black; in that case, dilute the platinumsolution with an equal volume of water. This deep yellow colorwith Solution A is a characteristic of platinum and iridium.

WITH GOLD

In another cavity, place one drop of gold solution, and add adrop of Solution A. After several moments add several more dropsof Solution A. Note the first intense dark color, deep purple orblack. This is characteristic of gold. After it stands a few minutes,notice the purple stain on the white porcelain.

Do not let the liquids dry on the plate. Wash it promptly aftereach test, removing any stains with a drop of aqua regia and rins-ing well.

Now, in another cavity, take just one drop of your gold solution,and dilute it with five drops of plain water. Take one drop ofthis dilute gold, in another cavity, and add a drop of Solution A.Note that the color is still definite. Dilute with five more drops ofplain water, and try again. See how dilute this gold solutionmust be before it becomes so weak that you cannot detect a changewith Testing Solution A. If you figure this out, you will find thatthis is a delicate test, one that will reveal the presence of a verysmall percentage of gold.

WITH PALLADIUM

In the same way, learn the color-changes shown when mixingstandard palladium solution with Testing Solution A. This color-change is even more interesting than the others. When the twodrops are first admixed, you see a deep yellow, not unlike the ef-fect produced by platinum. After some minutes the yellow turnsblue-green. This blue-green color is characteristic of palladium.

WITH SILVER

Silver solutions, such as silver nitrate, do not give any color-reac-tion with Testing Solution A. What you will see when the twoare mixed is a white cheesy precipitate of silver chloride, similar

to that obtained when table salt is added to a silver nitrate solu-tion.

WITH BASE METALS

Solutions containing only such base metals as iron, copper, zinc,nickel and cadmium give no color change with stannous chloride.Lead may give a white precipitate that looks like silver chloride,but if you employed the dichromate test in Chapter I this willcause you no confusion.

STANNOUS CHLORIDE TESTING SOLUTION WITH UNKNOWNS

You should now be ready to examine metals of whose composi-tion you are ignorant. Take an article that you suspect of beingplatinum or some platinum alloy. Rub it hard to make a goodstreak in a clean cavity of your spot plate. Dissolve the streak inaqua regia, noting whether or not it is necessary to heat the plate;and making up for evaporation if you do heat it.

Add a drop of Solution A and note the color change.Repeat with a piece of what you believe to be a good gold alloy.

Repeat with something you believe to be palladium. Finally asksome friend to hand you pieces of metal, preferably pure metalsor simple high-grade alloys, test them and check your reports withhim.

(Testing Solution A must be made up freshly from time totime. It loses its virtue completely in a few days. Therefore, be-gin the day's work by checking your Solution A against a drop ofstandard gold solution; if it fails to respond, throw it away at once.)

DETECTING GOLD, PLATINUM, AND PALLADIUM, IN THE PRESENCEOF EACH OTHER

The next step is to detect palladium in metal that is mostlyplatinum. This is especially valuable when testing dental alloysor buying metal that may be contaminated or of low grade. If youhave a standard needle of a platinum-palladium alloy, rub it onyour spot plate, warm the plate, dissolve the streak in aqua regia,and test the solution with Testing Solution A.

Can your eye detect the difference between that effect and theeffect produced by pure platinum?

Next, rub pure platinum in a cavity, and make a few rubs in thesame cavity using a bit of fine gold. Suppose you make fifteenrubs with platinum, and three rubs with gold. Again warm theplate, dissolve the streaks in aqua regia, and test with Solution A.

Can your eye detect the presence of that small amount of gold?Also, can your eye detect the presence of all three metals—gold,

platinum, and palladium—at the same time, in a single drop ofsolution?

Your eye may not be able to do this the first time. But after alittle experience, you will know which metals are present androughly the proportion of each.

Skill in appraisal comes with practice—practice in studying thebehavior of alloys of whose composition you are certain, exposingthem to the various tests and comparing them with each other andwith unknowns handed to you by some friend who can check yourreports.

If a spot plate is not obtainable, it is possible, though not con-venient, to use other plans. Thus, get a minute amount of yourunknown metal into solution in some other way, perhaps bycutting off a scrap with a file or saw and dissolving it in aqua regiain a tiny test tube or small watch glass. Soak up the solution inclean white blotting paper or filter paper. Now drop one drop ofTesting Solution A onto the stain. Colors will appear and spreadthrough the paper handsomely. If two precious metals are pres-ent, say gold and palladium, the characteristic colors of both willappear.

IF THE TESTS ARE NOT CONCLUSIVE—

The beginner sometimes gets confusing results. Sometimes thecolors refuse to appear. This may be due to the fact that one solu-tion or another has lost its potency. More likely it is because youhave used too much acid.

Remember that aqua regia weakens on standing. Rememberthat Testing Solution A spoils on standing. Both must be mixedafresh from time to time. The standard solutions do not spoil.If properly kept in glass-stoppered bottles they will keep for years.But when you make them up, do not use an excessive amount ofacid to dissolve your bits of metal. If too much aqua regia is used,the tests will be weakened or even destroyed.

The excess acid can be driven off by evaporating the solutionsgently until sirupy, then adding a little water. In dissolving thestreaks made on the spot plate, you sometimes use more aqua regiathan is wise. There again you can remove the excess by warmingthe spot plate gently; if the drop should go entirely dry, add plainwater to bring your substances again into solution.

Another situation that may confuse the beginner is to find analloy containing much platinum and very little palladium; ormuch gold and very little palladium. He finds that the palladiumcolor is obscured by the intense reactions of the platinum or thegold. As his eye becomes skilled he can detect smaller and smallerproportions; however, he will be glad to know that there is anothersolution that is especially valuable in detecting small amounts ofpalladium.

DIMETHYL GLYOXIME SOLUTION

This solution has the added virtue of showing up nickel, even insmall amounts. It will show up nickel in a platinum alloy; in awhite gold alloy; in a dental alloy; or in a solution. It will showup palladium and nickel when both are present in small amountsin an alloy that is largely platinum or gold.

Purchase a gram of dimethyl glyoxime. One gram will beenough for several hundred spot plate tests. Be sure to get a goodquality product. It is a white or pale yellow powder. The nameis pronounced "dye-methyl glyoxeem," but no one will blame usif we refer to it as DMG.

Dissolve this gram of DMG by bringing it to a boil in about 100cc of water—about 4 fluid ounces. The powder dissolves ratherslowly. Let it cool and if possible let it stand overnight; thenfilter. It is important that the solution be clear and free fromsediment or crystals. It is now ready to be placed in a droppingbottle, which should be labeled DMG. It keeps quite well for years,except that you may have to filter it again.

Let us get acquainted with DMG. Its most interesting charac-teristic, as we said, is to show up palladium and nickel, in the pres-ence of other metals and in the presence of each other.

DMG AND PALLADIUM

First, place a very small drop of the standard palladium solutionin a cavity of the spot plate. Or, better, take one drop and diluteit with several drops of water to obtain a pale yellow solution;then place one drop of the pale solution in a clean cavity.

Do the same thing with a drop of your standard platinum solu-tion, and with your standard gold solution; a drop to a cavity. Allthree have a pale yellow color.

Now add a drop or two of DMG to each cavity. Note the PRECIP-ITATE that forms, and its color. Note that the pale yellow colorsdo not change, but that in the cavity containing palladium youwill see a PRECIPITATE, or sediment. Note carefully that whileTesting Solution A gives prompt changes in color, DMG distin-guishes between palladium and the other metals by forming a pre-cipitate.

You can see this more clearly by making similar tests in small testtubes. Make one test with an extremely dilute palladium solution,adding DMG and noticing that even very small amounts of thisyellow precipitate are visible.

Be sure in the beginning that all your test solutions are clear andfree from precipitates or flocculence; otherwise you will be de-ceived.

DMG AND NICKEL

Scratch on the spot plate with a five-cent piece. Dissolve thestreak with a drop of nitric acid or aqua regia. Add a drop or twoof DMG. Nothing special will happen.

Now, add a big drop of ammonia. If you used enough ammoniato kill the acid, you will see a very beautiful and characteristic colorchange.

From one point of view it is a waste of time to describe thesecolor changes, since they become of value only through being seenby each observer. However, for the sake of the record we may saythat this color, produced by DMG, nickel, and ammonia, is astriking rose-red. And the precipitate produced by palladium andDMG in acid solution is canary yellow.

Note this particularly: The test for palladium appears only inACID solution; the test for nickel must be made in AMMONIACALsolution.

This is very handy. Thus, suppose you have a piece of so-calledplatinum as an unknown, and you suspect that it may containboth nickel and palladium. First make the streak on the spot plateand get it into solution with aqua regia. Then add DMG. If pal-ladium is present you will see the copious precipitate, canary yel-low in color. Now add enough ammonia to make the mixturesmell faintly. If nickel is there, you will at once see the beautifulrose-red. All in one cavity of your spot plate.

Continue to test various scraps of metal, such as cheap whitegold, (which is almost sure to contain nickel) and high-gradedental alloys, (which are almost sure to contain palladium). Thesetests are so fascinating that it will be no hardship to practice untilyour eye is quite thoroughly trained.

THE SPOT PLATE AND AN UNKNOWN

With the facts already learned, the clever observer is now readyto test a wide variety of unknown metals. Suppose you have apiece of jewelry, and you suspect it of being palladio-platinum,possibly containing gold and nickel. Let this diagram representthe cavities in the spot plate:

o o o oo o o oo o o o

Now make scratches with your unknown in the three cavities tothe left. Make from 10 to 25 scratches in each cavity; with softmetals a few scratches are enough; with hard ones use more. Countthe scratches, so as to use the same number every time in a giventest.

In the second row of cavities, make scratches with some metal ofknown composition, whose nature you believe to be similar to yourunknown. Let us call this alloy a; the unknown will be called x.Thus, suppose you suspect your unknown of being approximately20-80 palladio-platinum. In that case, the second scratches shouldbe made with a needle of that composition.

In the third row of cavities, make scratches with some other

combination of metals, which you suspect may resemble your un-known x. For example, you might make fifteen scratches withpure platinum and five scratches with fine gold. Call this alloy b.

In the fourth row it might be useful to make scratches of somefurther combination which may or may not resemble x. For ex-ample, make fifteen scratches with pure platinum and five scratcheswith a piece of pure nickel. Call this c. Your spot plate will nowlook like this:

xoxoxo

aoaoao

bobobo

CO

CO

CO

The next step is to dissolve every one of these streaks in aquaregia. With platinum alloys you must heat the plate. Into eachcavity drop exactly the same amount of aqua regia. Give thestreaks time to dissolve; indeed, you can gather considerable in-formation regarding your unknown by noticing the promptnesswith which it dissolves in aqua regia. In some cases the colormay prove helpful; you will recall that both copper and nickelgive green solutions; unfortunately gold, platinum, palladium andiridium all give the same color here—yellow.

After the streaks have all dissolved, begin your tests. Startingat the top, place about three drops, more or less, of Testing Solu-tion A in each of the four top cavities. Now, to the middle rowof four cavities, add two or three drops of DMG. Use the samenumber of drops in each cavity of a row. In the bottom row,add first a big drop of ammonia, then one or two drops of DMG.

Compare the way in which your unknown responds to thesetests, with the reactions caused by alloys or mixtures whose natureyou are sure of. Sometimes it helps to let the spot plate stand awhile—half an hour, or overnight. New colors may appear.

If your unknown is strikingly different in its reactions from yourknowns, then start in all over again, after cleaning your spot plate,using another set of knowns.

These suggestions will readily bring to mind other possible ar-rangements. The success of this method lies in practice, care, agood memory and a good light. Also in keeping your spot plateclean.

To DISTINGUISH BETWEEN IRIDIO-PLATINUM AND

RUTHENIO-PLATINUM

In some ways this test is more difficult than most; hence it is es-sential to practise with samples of both alloys until you are sureof the method. You will use the spot plate, aqua regia, some full-strength C.P. ammonia, and a few crystals of sodium thiosulphate—also called "hypo" and obtainable from any photo or chemicalsupply shop.

First make thirty scratches in a cavity of the spot plate with theiridio-platinum. In another cavity make thirty scratches with theruthenio platinum. Heat the plate as usual, and dissolve thestreaks in aqua regia. However, since these alloys are so slow toreact, you probably will have to add more aqua regia, a drop at atime, to make up for evaporation. Do not let the cavities go dry; itmay help to add a drop of water.

It usually takes about ten minutes for the streaks to dissolve.Sometimes the particles of metal float loose from the porcelainbefore they really dissolve. Keep the plate hot.

When all the metallic particles have dissolved, add to each cavitytwo or more drops of ammonia—enough to make the solution defi-nitely ammoniacal. Warm again, being careful not to let the spotsgo dry, adding a drop of water or of ammonia to keep things insolution.

Finally, add to each cavity a small crystal of sodium thiosulphate(hypo). In the ruthenium solution you will see a red or pink color

within two or three minutes. Compare it with the iridio-platinumsolution, which shows almost no color change.

That is all there is to the test. Its only difficulty is that thesealloys dissolve so slowly, even when the plate is hot, that some ob-servers lose patience and give up before the test has had time to act.Also, it is necessary to keep the spots from going dry, and this re-quires some watchfulness.

This reaction was reported first by Carey Lea, and its use for thispurpose was suggested to the writer by Raleigh Gilchrist of theUnited States National Bureau of Standards.

SECTION C. SOME OTHER TESTSThere are many other tests used by chemists and metallurgists

for the identification of metals. Those already given will servemost purposes. The following tests, however, are included inthis chapter because of their long usage and for their value in spe-cial applications.

IODINE TEST FOR PALLADIUM

Place a drop of tincture of iodine, the kind found in most familymedicine kits, on a piece of palladium or an alloy that is rich inpalladium. Heat with a small flame—-a match will do—until thealcohol in the tincture takes fire and the liquid dries. A blackstain of palladium iodide will remain, to be removed only by vig-orous rubbing. Repeat, using platinum or a nickel-gold; while astain will form, it is less deeply colored and can be easily rubbed off.

THE GLOW TEST

One peculiarity of the platinum group metals is their ability tosoak up gases. This is utilized in one kind of cigarette lighter, inwhich some finely-divided palladium can be exposed to naphthafumes; it soaks up the fumes and in so doing becomes hot, andfinally the fumes ignite. This phenomenon can be used as a testfor platinum group metals in some cases. However, many sub-stances inhibit the test, while others (such as copper) may producea false glow, so the test has fallen into disuse, and is not recom-mended for our purposes.

ANOTHER TEST FOR GOLD

Ferrous sulphate (also called copperas) is often used as a testreagent for gold in aqua regia solution. Before making the test,heat the solution gently almost to dryness and add a little plainhydrochloric acid, then again evaporate almost to dryness. Thisis to remove all excess nitric acid, whose presence interferes withthe test. Now add a little water and a crystal of the pale green fer-rous sulphate, and after a few seconds a dark cloud of finely dividedmetallic gold will appear.

ANOTHER TEST FOR PLATINUM

In the refining and purifying of platinum, it is customary toadd ammonium chloride to an aqua regia solution of the metal,and a yellow powder will precipitate out. This powder, whosecolor ranges from canary yellow to deep orange, is platinum-am-monium-chloride. It is collected and converted back into metal-lic platinum.

This same reaction can be used to identify platinum. Dissolvea scrap of metal in a little aqua regia. Dissolve some ammoniumchloride in a little water to make a concentrated solution, and addit to the acid solution. Watch for a yellow or orange precipitate.Practise with your platinum samples before attempting to identifyunknowns. You will find that this test is not as delicate as someothers, for if there is only a little platinum in solution, no precipi-tate will be visible. Some people add the ammonium chloride asa dry salt; this is not wise, for you may mistake its crystals for theyellow powder that you are seeking.

Potassium chloride can be used in this test instead of ammoniumchloride.

This test is a favorite with prospectors, and is dependable whenproperly used. However, wishful thinking has led at least a fewworkers to mistake sand and other worthless materials for theyellow or orange precipitate. It is wise to practise with severalores and minerals known to contain platinum, before attemptingto identify unknowns.

OLD AQUA REGIA SOLUTIONS

Men who work with the precious metals have frequent occasionto dissolve them in aqua regia, for example as the first step in thepreparation of a gilding bath, or in the refining of factory wastes.It is not unusual to find accumulations of these old solutions, some-times heavily contaminated with other metals. Methods of ap-praising such solutions differ with circumstances, but in generalwe utilize the principle discussed in Section B of this chapter.That is, drop-size samples are tested in the cavities of the spot plateagainst the various testing solutions until the components are es-tablished. Then by comparison with the Standard Solutions (inwhich a known weight of metal is dissolved in a known volume of

liquid) we can roughly estimate the weight of metal in a givenvolume of unknown solution. This calls for skill and patience, thedrop-size samples being diluted with one or more drops of wateruntil the intensity of the color-reactions of the unknown solutionapproximate the intensity of the color-reactions given by theStandard Solutions. This problem, which is hardly one for thebeginner, is discussed in more detail in the book Refining PreciousMetal Wastes, by C. M. Hoke, published by the Metallurgical Pub-lishing Company, 123 William Street, New York.

TESTING ALKALINE SOLUTIONS

You will observe that in the tests so far described, the solutionshave been mildly acid or neutral. Never strongly acid—excess acidwill weaken or even ruin most of them—nor alkaline, except inthose cases where an ammoniacal solution was used. Testing Solu-tion A will not work at all in alkaline or cyanide solutions, untilthe alkalinity is destroyed. Thus, suppose you have an old cyanidegilding solution, and wonder if it contains dissolved gold: Takeabout five drops of the suspected liquid in a small test tube ortiny dish, stand near a window or an exhaust fan, and carefully addfour or five drops of hydrochloric acid. The fumes evolved are ex-tremely poisonous—hence the need for working near an exhaust.Bring the mixture cautiously to a boil; this drives off the cyanide.Let it cool, and you can now use Testing Solution A or ferrous sul-phate the same as usual.

Success with all these tests calls for practice, patience, and a goodlight. It also requires keeping your spot plate clean.

ELECTROGRAPHIC TESTS

A clever electric method for detecting gold, chromium, and someother metals in alloys or electrodeposits has been worked out byJ. A. Calamari, Robert Hubata, and P. B. Roth of the New YorkMedical Laboratory in Brooklyn. The test is easy to perform*need not injure the article, and requires only simple equipment.The article to be tested is wired to the positive pole of a battery, 6to 9 volts, and a pad of filter paper or white blotter, wet with a solu-tion of sodium nitrate and hydrogen peroxide, is laid on it. Agraphite rod connected to the negative pole is touched to the wetpaper.

If the paper is in contact with gold, a purple spot appears. Mostbase metals give no reaction, but chromium gives a blue spot, silvera black spot, and so on, and the intensity of the color may suggestthe karat or composition of the surface layer. The method is de-scribed fully in Industrial and Engineering Chemistry, July 16,1942.

For our purposes this method has the disadvantage of centeringattention on the surface of the article, which as we know may bequite different from the bulk of the piece. But when properly ap-plied and understood, it is very useful.

SPECIFIC GRAVITY

Even in prehistoric days people noticed that some metals wereheavier than others, and that the precious metals in general areheavier than the common ones. These differences are utilized inmany ways; thus the prospector shakes the gold-bearing gravel in apan, with water, and the heavier gold particles settle to the bottom.These differences have also been used, for centuries, in identifica-tion and appraisal.

The story is that Archimedes, a Greek mathematician of thethird century B.C., was asked by his king to determine if a crown,purporting to be gold, did not actually contain some silver—aproblem of precisely the type that confronts the readers of thisbook. Archimedes was puzzled, until one day as he stepped intohis bath and saw some water overflow, it came to him that theexcess of bulk caused by the introduction of a lighter alloyingelement could be measured by putting the crown and equalweights of gold and of silver, separately, into a bowl of water, andnoting the difference of overflow. The story continues that Archi-medes was so overjoyed at this happy thought that he ran homewithout his clothes, shouting "Eureka! Eureka!," meaning "I havefound it!"

This ratio between the weight and the bulk of an article is calledits density or its specific gravity—"specific" because each pure ele-mental material has its own unique and specific ratio. The pro-cedure for determining it is given in the Appendix.

Pure water is commonly used as a standard of comparison, withthe specific gravity of 1.00. A cube of water measuring 1 centi-

meter on a side weighs 1 gram. A cube of gold of the same sizeweighs 19.32 grams, and has a specific gravity of 19.32. Silver,lead, palladium and mercury occupy a middle group with gravitiesrunning from 10 to 13. Tin, zinc and steel are all close to 7; alumi-num is 2.7; platinum is 21.37. Gases, and things like cork thatfloat on water, have specific gravities of less than 1, usually repre-sented by a decimal.

Alloys have densities that range between those of the compo-nents. Thus a palladio-platinum alloy will come somewhere be-tween pure platinum and pure palladium, and its specific gravitywill suggest its composition. Sterling silver can be distinguishedfrom silver alloys of lower grade. Iridio-platinum can be distin-guished from ruthenio- or palladio-platinum. High karat goldsare heavier than low karat. And so on.

However, the method has its limitations. For example, bymanipulating the components it is easy to make up several alloysof the same density but different compositions. If a bar containsbubbles or blow-holes its density will be less than that of a homo-geneous bar. If such a bar were drastically rolled its specific gravitywould increase. If a piece of jewelry contains stones, these mustbe removed before a significant specific gravity determination canbe made. In general, the smaller the article, the less accurate thedetermination.

In the Appendix will be found a list of metals with their den-sities and melting points, as well as their responses to nitric acid,to hydrochloric acid, and to the oxy-gas flame.

CHAPTER V

Buying and Selling Old Precious Metals

CAN I make money buying and selling old gold? "Where canI buy it?" "To whom can I sell it?" "Must I have a license?"

"How much is this old silver worth? This platinum? This pal-ladium?"

"What is the most profitable kind of old precious metal tohandle?"

"Will it pay me to buy up a lot of old filled watchcases andplated spectacle frames?"

"Is it true that this line is full of grafters?""I paid eighty dollars for this watch; why is it the jeweler will

give me only three dollars for it now?"These and other related questions come up repeatedly. This

chapter will try to reply to them, and to be helpful both to thelayman (or lay woman) with some jewelry to sell, and to the jeweleror antiquarian who might buy it.

THE FOUR STEPS

There are four steps in the process of buying and selling oldprecious metals. First the metal must be identified. We makesure that it is gold and not brass, and we determine its karat qualityas accurately as we can. Or we make sure that it is silver all theway through, and not silver plated. Or we decide that it is plati-num of high quality; or of low quality. The details of this firststep have been described fully in the first four chapters of this book

The second step is to find out how much the article weighs. Thefinal steps are to calculate its value and to find a purchaser whowill pay the highest price. Let us now consider these steps in turn.

WEIGHING PRECIOUS METALS

We often see pictures of Justice holding a balance in her hand.But in real life we get much more just results if the scales are sup-

ported on a strong and rigid frame, carefully leveled so that thebeam, when at rest, lies truly horizontal. Indeed, the use of a handbalance in trade is generally forbidden by law, for a clever swindlercan tip a hand balance in his favor, and even an honest hand can beunsteady.

The troy system of weights is commonly used with the preciousmetals. Its basic unit, the grain (gr.) is of the same weight as thegrain used in the apothecaries' and avoirdupois scales.

24 grains = one pennyweight (dwt.)20 dwt. = one troy ounce (oz.)12 troy oz. = one troy pound (lb.)

The pound is rarely mentioned, which is just as well, for it dif-fers just enough from the generally-used avoirdupois pound tomake for confusion. For small quantities there is a growing tend-ency to use decimal parts rather than to mention two units. Thus,instead of saying 20 ounces 10 pennyweight, we might say 20.5 oz.Instead of 15 pennyweight 6 grains, we might say 15.25 dwt.

The seller must remember that a swindler can use an honest bal-ance but dishonest weights. Some of the itinerant old-gold buyersthat flooded the land during the depression of the '30's were saidto use a copper cent, weighing about 50 grains, instead of a penny-weight (24 grains), thus obtaining twice as much gold as they paidfor. The difference between the troy ounce (480 grains) and thelighter avoirdupois ounce (437.5 grains) has also been used to thedisadvantage of the unwary.

As we said, the troy system is in general use with all the preciousmetals. However, scientific workers, accustomed to the metricsystem, like to buy and sell their platinum group metals by the

gram or milligram, and the well-equipped metal buyer will havea set of gram weights in addition to his troy weights.

A good balance is a sensitive and expensive instrument. Itshould be sheltered from dust and draughts, and must stand on afirm level table, free from vibrations. Weights should be kept ina covered container, and should be picked up with tongs made ofa relatively soft metal—never touched with the fingers. You canlearn something about a person and his establishment by observ-ing how he handles his balance and weights.

THE "OLD GOLD" INDUSTRY

For generations—until the depression of the 1930's—the buyingand selling of old gold had been an inconspicuous industry. Thesums involved were small, and there were only a few simple regula-tions. Few jewelers sought such business, and when it came tothem they carried it on apologetically in the back office.

Then, after Great Britain went off the gold standard, the picturechanged. The purchasing power of gold began to rise all over theworld. Prospectors got out their rusty shovels and went into thehills. Itinerant gold buyers went from house to house picking upunused trinkets. In 1933 the United States called in all gold coins,and our gold price, which for years had been $20.67 an ounce,started the step-by-step climb that finally was pegged at $35 anounce by the Gold Reserve Act of 1934.

With this increase in value—a rise of almost 70 percent—the oldgold business mushroomed into an important industry involvingthousands of people and millions of dollars. Jewelers hung the"We Buy Old Gold" sign prominently in their front windows. So-called refiners' agents opened up on every Main Street, whilehouse-to-house canvassers swarmed over the country by the thou-sands. Some of these latter were honest and intelligent, but manywere patently dishonest, and most of them were deeply ignorant ofmetal values. (For example, since their main interest was in theyellow metal, gold, few of them learned how to appraise platinumand white gold, or even to recognize them.)

This feverish and unwholesome activity was finally calmed,partly by legitimate competition, partly because federal and localregulations put the fly-by-night and the crook out of business.

Since then the buying and selling of old precious metals has beenstabilized on a higher plane, and is now largely in the hands ofmen who, like jewelers, have a knowledge of metals and integrityin handling them.

FRAUDS AND MISUNDERSTANDINGS

No doubt there has been much deliberate deception in thehandling of the precious metals. There have also been many hon-est mistakes. This book has repeatedly mentioned certain neces-sary precautions—allowances for solder, the need to penetrate intothe inner layers of metal; stainless steels that resist the usual acidtests; the wisdom of testing white and green golds with white andgreen gold needles; the wisdom of testing all parts of complex ar-ticles such as watchcases, and so on. It is indeed true that suchprecautions are needed, as was revealed some years ago whenseveral jewelers, men used to handling gold, were deceived bystainless steel.

The experienced jeweler tends to judge the worth of an articleby the workmanship upon it—if the workmanship is good, he ex-pects the metal to be worthy. This tendency has been traded uponby a few unscrupulous persons, and fake antiques, of excellent de-sign and craftsmanship, have appeared on the scene.

However, for every single instance of this kind, there are thou-sands of honorable transactions. Some of these latter, however,have been misunderstood by the layman. Thus: A woman bringsin a watch, now useless, but once highly prized; the jeweler offersher a few dollars, representing only the old metal value; he cangive her nothing for the mechanism, nothing for the labor orig-inally put into the case, nothing for the fashion element that onceaccompanied it, and not a cent for the profit that the originaldealer made when he sold her the trinket. Situations such as thisoften mean disappointment to the seller, but reflect no discrediton the buyer.

"WHO WILL BUY MY GOLD?"

The layman with a few pennyweight of gold will generally dobest to take it to a neighborhood jeweler of good repute. Large lotsprobably should be sold to Uncle Sam. If his community has nojeweler, his bank will advise him as to the financial stability of

someone nearby. A jeweler will explain the value of the metal,and if there are any precious stones he may purchase them as well.If the article has artistic merit the jeweler may indeed pay morethan the mere old-metal value and purchase the article for re-sale.

The professional refiner sometimes—not always—will pay a fewmore cents a pennyweight than the jeweler. However, he rarely isinterested in artistic merit nor in precious stones. There are pro-fessional refiners in most large cities, and their agents can be foundalmost everywhere and are usually glad to be of service to the lay-man.

The retail jeweler who buys old precious metal will sell it toUncle Sam or to a professional refiner, his choice being governedby considerations that will be discussed later in this chapter. Themanufacturing jeweler will probably refine his purchases and usethe metal in his own shop, or perhaps he will turn it in in exchangeto the metal dealer from whom he buys his raw material.

When jewelers buy old gold from the public, the appraisal isnormally made on the basis of the quick tests with acid and touch-stone that have been described in these chapters.

When the Government buys gold or gold-bearing material, itmelts down every lot, mixing it thoroughly, takes a sample andassays it carefully. Payment is made on the basis of this assay.This procedure takes a few days, but naturally gives an accuratevaluation which leads to greater satisfaction all round. Very smalllots are not accepted.

When refiners buy metal, they usually employ the quick touch-stone tests for small lots, while large lots are melted together, sam-pled, and assayed.

U. S. GOVERNMENT REGULATIONS

The regulations imposed by the United States Government weredesigned originally to prevent hoarders who in 1933 had violatedthe law by failing to turn in their gold coins at the old value, fromprofiting when the price of gold was increased. These regulationsnow apply to all transactions involving any substantial quantity ofgold, and have proven of great protection to the public and thelegitimate dealer.

During World War II all the metal industries, both base and

noble, underwent many changes due to shortages and war restric-tions, and more regulations were imposed, mostly on the manufac-ture of specific metal articles.

Since all such regulations are subject to change, it would be idleto repeat them here. The interested reader should obtain copiesof current regulations from time to time, as he needs them, fromhis nearest Federal Reserve Bank, or the Mint or Assay Office ofhis district.

For many years the regulations regarding Uncle Sam's purchasesof gold were quite simple; he would purchase gold in almost anyform from anyone, and no questions asked. Each lot had to be ofa certain minimal quality and total value. A small charge wasmade to cover the refining of the material, the rates varying slightlyfrom time to time. Shipments were made by hand or express tothe owner's nearest Mint or Assay Office. The government hasnever employed any traveling agents, and has publicly stressed thepoint that the Mint has no agents soliciting for it.

"MUST I HAVE A LICENSE?"

Since we went off the gold standard, the regulations now in-volve the licensing of those who acquire, transport, melt or treat,import, export, or earmark gold in substantial quantities, orhold it in custody for foreign or domestic accounts. The rulesregarding Uncle Sam's purchases of native gold, old jewelry, etc.,have also been modified in almost every detail. These rulings aresubject to further change without notice.

Several kinds of licenses are provided—all being described fullyin the Regulations. Application forms for the various licenses canbe obtained from the Office of each District; these must be filledout in duplicate and sworn to before a Notary Public, and returnedto the Office of the District, with such further information as theRegulations require.

No charge is made, and in general if a man has been establishedin some branch of the precious metals industry or has legitimateneed for gold, he will not be refused a license.

One of the requirements of licensees is that they should not dobusiness under a name which would induce the belief that goldis being handled on behalf of the Government or for the purpose

of carrying out any policy of the Government. In other words,Uncle Sam does not want gold-buyers to pose as his agents.

Many states and cities require local licenses in addition to theFederal license. Local regulations are aimed at preventing thesale of stolen goods and the fleecing of uninformed sellers.

THE MINTS AND ASSAY OFFICES

The Denver Mint takes care of applicants from the followingstates: Colorado, Iowa, Kansas, Minnesota, Nebraska, New Mex-ico, North and South Dakota, Oklahoma, Texas, Utah, and Wy-oming.

The Assay Office at New York takes care of Connecticut, Del-aware, Maine, Massachusetts, Michigan, New Hampshire, NewJersey, New York, Rhode Island, Vermont, and Wisconsin, PuertoRico, Virgin Islands, and Canal Zone.

The Philadelphia Mint takes care of Alabama, Arkansas, Flor-ida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maryland,Mississippi, Missouri, North and South Carolina, Ohio, Pennsyl-vania, Tennessee, Virginia, West Virginia, and the District ofColumbia.

The Seattle Assay Office takes care of Idaho, Montana, Oregon,Washington and Alaska.

The San Francisco Mint looks after Arizona, California, Nevada,and the territories and possessions not otherwise mentioned.

UNCLE SAM DOES NOT BUY PLATINUM

One government regulation of peculiar interest is that coveringthe platinum-group metals. The Mints and Assay Offices do notwish them and, if they are included in a shipment Uncle Sam willnot pay anything for them. In fact, his refining charges will bethat much higher, because of the extra labor involved in assayingand refining material that contains these metals. The moral isplain—sell your platinum to one of the many dealers who will paya fair price for it. This metal will be discussed again in this chap-ter.

WHAT TO DO WITH SILVER

At certain times in our history Uncle Sam has bought silver aswell as gold. The world price fluctuates from day to day, being

influenced by political and financial conditions at home andabroad. Quotations will be found in the daily papers.

Meanwhile, though silver is not high, there is a good market forit, and if one has a quantity of old sterling silver he can sell it to aprofessional refiner, especially one who is equipped to make it intosheet, wire, or the like, and to sell it for making up new goods.Several refiners specialize in silver, and silver is always accepted bythe Government as an integral part of a deposit of gold that com-plies with its regulations—that is, silver that serves to alloy thegold.

Silver plated ware is of such small value today that in generalit is not traded in except by those who happen to have manypounds of it. Usually this is sold to a copper refinery, where itgoes through the same electrolytic process that is used in refiningcopper; the silver is recovered as a by-product.

"How MUCH IS PAID FOR OLD GOLD?"

At present writing, the Government price of fine gold is $35.00a troy ounce, or $1.75 a pennyweight. Ordinary gold contains moreor less base metal, and is worth correspondingly less. There is al-ways a "spread" between the buying price and the selling price ofany article, to provide for the handler's living, and gold is no ex-ception to the rule.

Previous chapters of this book have told how to establish thekarat or quality of a gold article, and how to establish whether agiven article is solid gold or merely gold filled or plated.

An experienced purchaser will allow a leeway of one or twokarats, for solder or for errors in testing. That is, suppose a ringseems according to the touchstone test to be a full 14-k; he willstudy its design to see whether it required much or little solder,and possibly he will decide that the ring as a whole would assay13-k. As mentioned in earlier chapters, chains and mesh usuallyhave more solder per unit of weight than other articles, and achain whose links are 14-k may assay 10-k to 11-k.

THE GOLD-BUYER'S ROUTINE

Here is a procedure that probably would be followed by ajeweler when buying gold in small quantities with the expectation

of selling it eventually to a refiner. He establishes its average karat;finds the weight in pennyweights; then multiplies the karat timesthe weight times about 5^ to 51/^ for the purchasing price. Hecan expect the refiner to pay him about 6^ to 61^^. (These fig-ures are all based on fine gold at $35 per ounce.)

For example: An old ring mounting seems to be 14-k on thetouchstone; the design requires very little solder and there are noindications that repairs have been made. Assuming that the av-erage quality would be at least 13-k, and noting that the weight is3 dwt., he multiplies 13 x 3 x 51/2^ The answer is $2.14^4, andrepresents the price he would pay to the seller. He hopes to sellthe article to a professional refiner for 13 x 3 x 61^^, or $2,531/2-The difference of 39^ is his profit and must pay for his time in mak-ing the touchstone tests, the cost of shipping to the refiner, and soon. By buying for a little less than 51/^ sometimes, and occasion-ally selling for a bit more than 61/2^ the profit may run fromabout 18 percent to 30 percent on the investment, with 25 percentas an average.

To the jeweler, this transaction has another aspect. It has ledsomeone to enter his store and make his acquaintance. The profitmay well be small, but it often leads to further business with alarger return. For this reason many jewelers figure on a very nar-row "spread" between the buying and the selling price of theirold gold business, and thus build up good will.

On the basis of 6i/2<j; per karat per pennyweight, a refiner wouldpay 65^ for a pennyweight of 10-k gold, $1.23 for a pennyweight of18-k gold, and so on. When a refiner buys a large quantity ofclean old jewelry or scrap, enough to justify a chemical assay (in-stead of an appraisal based on touchstone tests) he may pay morethan 61/2$ per karat per pennyweight. Some kinds of old metalare more difficult to refine than others, because of the quantity andnature of the base metals present, and this factor also may affect theprice.

FILLED, ROLLED AND PLATED GOODS

Gold filled and rolled gold stock, so much of which is used inspectacle frames, watch cases, and moderately priced jewelry, ismuch less valuable. It may bring 25^ to 75^ an ounce. It is im-

portant to remove all nonmetal or base metal parts before weigh-ing. Note that this price is for an ounce, not a pennyweight. Goldplated stuff is worth even less; possibly io f to 15^ an ounce. UncleSam does not buy it, and most refiners receive it without enthusi-asm if at all, except when very large lots are available.

BUYING AND SELLING PLATINUM GROUP METALS

The market for old platinum metals is not as well standardizedas that for gold and silver. The Mints and Assay Offices do notbuy these metals from the public. The layman with a few penny-weight of platinum jewelry to sell will generally do best by takingit to his neighborhood jeweler, if possible to the one from whomit was originally bought. The jeweler or old-metals buyer shouldseek a refiner who is active in this market. Certain refiners special-ize in these metals, while others specialize in gold or silver. Makersof scientific apparatus, dental supply houses, or jewelers who useplatinum in the manufacture of their wares, should also be con-sidered. Since these metals have many wartime applications andhave at times been under restriction, enquiry should be made as tothe legal aspects of any sale or purchase.

These metals normally have fluctuating prices. Quotationsmay be obtained from dealers or from trade papers. At certaintimes the Government has established fixed prices.

As we learned in Chapter IV, some of these metals are easilyidentified, and thus easily appraised, but many of the alloys andcombinations are fairly difficult to identify, and even more diffi-cult to appraise. Several different alloys or combinations areused in jewelry, and in the various technical fields the number ofalloys and combinations, with or without gold or silver or basemetals, is legion. These all look a good deal alike but differwidely in value. The situation is further complicated when abase metal core is completely encased in only a thin shell of pre-cious metal.

A complete chemical assay for the exact determination of thesemetals is longer and more costly than one that involves only goldor silver, and becomes increasingly difficult with each additionalelement to be determined.

The refining of scrap or waste metal for the recovery of thesemetals, and the purification that may be needed to prepare themfor resale, are in general more time-consuming than similar tasksin which only gold or silver are to be recovered. And there arefewer workers qualified to do such work.

THE PLATINUM "SPREAD"

Because of the complications just described, the "spread" be-tween the buying and the selling prices of the platinum-groupmetals and their alloys is wider than the "spread" for gold or silver.Thus, when a prospective buyer is calculating what to pay you foryour scrap platinum-group metals, he recalls the difficulties ofidentification and appraisal; he remembers that a complete assaymay be a slow and expensive job; he reflects that it may not beeasy to refine and repurify what he buys; and he recalls that themarket price of these metals may suddenly drop. Accordingly hequotes you a buying price that will be low enough to take care ofall these factors. And when he comes to sell the refined metalagain, his selling price must be correspondingly high.

Sometimes one can return scrap platinum, such as old chemicalware, to the original dealer from whom it was bought. If so, andif the article is still in recognizable form, he may well offer ahigher price than usual, since he knows its composition and neednot figure in the cost of appraisal and testing.

METALS USED IN DENTISTRY

Yellow gold fillings are high quality gold—22-k or so. The mod-ern cast fillings are sometimes of lower karat. Dentists often placefillings of much less expensive materials in the back teeth, wherethey will not show; some of these turn dark or even black. Fromthe standpoint of the patient's benefit these fillings are often ofthe highest value, but to the old-gold buyer they are not attractive.

Old fashioned false teeth were, in many cases, provided withtwo small pins of high-grade iridio-platinum. Much of the workdone today may contain no precious metal at all, so each job mustbe considered individually.

Many of the dentures of today are made of gold-platinum-pal-ladium alloys, some of which at times are worth more than fine

gold. They often look like so much nickel, being white or of aslightly yellowish white color, but a few of the tests described inthis book will quickly prove their value.

Scrap metal of this type can, in general, be sold to best advantageto a dealer in dental alloys, since he can most easily appraise it.

"ARE WHITE METALS THE MOST PROFITABLE TO TRADE IN?"

It is being said that platinum, white gold, and the whiter dentalscrap are the most profitable part of the "old gold business" today.This will doubtless be the case for some time in the future. For onereason, most of the early house-to-house canvassers did not knowhow to identify platinum or palladium, and distrusted any white-looking alloy, and therefore refused to purchase many very valu-able offerings. This led the owners to place a lower value onsuch articles. Accordingly when a buyer appears who knows howto judge such metals, he can pick up excellent bargains.

The reader may have wondered why so much space was devotedin this book to methods of identifying and appraising platinum,palladium, white golds both high grade and low, and other whitealloys. The reason should now be clear—so few people are familiarwith these tests, and there is so much neglected value on the mar-ket.

FACTORY WASTES, FILINGS, SWEEPS

When a jeweler makes a piece of jewelry, he starts with a sheet ofmetal and he hammers it and drills holes in it, and files off therough edges; possibly he engraves it. He winds up with a pieceof jewelry that weighs one-half or maybe only one-tenth as muchas the original sheet. The rest is now in the form of scrap, filings,and minute particles such as those that are swept up from the fac-tory floor, all contaminated with more or less dirt.

The large and relatively clean pieces he will wash and melt upfor immediate re-use. The smaller scraps and filings have variouskinds and amounts of trash mixed with them—steel from the files,emery from the emery cloth, tobacco, binding wire, bits of paper,possibly shellac from the stone-setter's bench, and what-not. Therefining of such materials is part of the routine of most jewelryfactories; the paper and other organic matter is burned out, steel

is removed with a magnet, nitric acid will dissolve out other basemetals, and so on, the exact procedure depending upon the char-acter and proportion of the trash and impurities. If his filings con-tain both gold and platinum metals, he will wish to separate thesechemically and recover them in pure form. This calls for someadditional procedures, all well within the facilities of mostjewelry shops.

Some of the original precious metal will, however, be in evensmaller particles, admixed with a larger proportion of dirt. Thusit is the custom in jewelry shops to save carefully the sweepingsfrom the floor, to filter the water in which the men wash theirhands, to burn the polishing cloths and save the ashes,—all be-cause these wastes contain enough precious metal to justify theseefforts. The refining of this third group of wastes, this low-gradegroup, is a much more difficult matter. While it is shop routine torefine the high and medium grades, only the exceptional plantshould attempt to refine low-grade wastes. The custom is to burnand sieve them, perhaps to subject them to other treatments, thenfor their ultimate refining to sell them to a professional refinerwho can give them proper large scale treatment.

The scrap and grindings brushed from the work-table of thedental mechanic have many of the characteristics of jewelers'wastes, and are treated in the same general manner. Jewelers,platers and others all have occasion to dissolve precious metals inacids or other solvents, producing solutions of varying compositionand value. Sometimes the owner recovers the dissolved metal him-self; sometimes he must sell it to a professional refiner. There areseveral other industries—photography for one—that generate pre-cious metal wastes, and mostly they are of such a nature that theirrefining, as in the case of the jeweler's sweeps, is best carried outon a large scale.

Here, then, is another field of activity for the buyer of old metals.He can act as a refiner's agent in purchasing such factory wastes asthe owners cannot or will not refine at their own plants. And per-haps he can complete the industrial cycle by selling the refinedmetals back to the jeweler, dentist, or other worker.

It should be clear that co-operation and understanding betweenthe gold buyer and the refiner, as well as between the several other

segments of the precious metal industries, can work to the ad-vantage of all concerned. The fostering of such understanding isone of the purposes of these chapters.

(Methods used by jewelers, professional refiners, and others inthe recovery of pure precious metals from the various kinds ofscrap, filings, solutions, sweeps, and the like, are described fullyin the book Refining Precious Metal Wastes, by C. M. Hoke, pub-lished by the Metallurgical Publishing Co., 123 William Street,New York.)

THE PROFESSIONAL REFINER

The refiner has, as we have seen, several important functions inthe economy of the precious metals. In some parts of the countrythe bulk of his work is the refining of ores and concentrates shippedto him directly from the mines. All refineries have facilities forsampling and assaying the materials that come to them. In otherparts of the country the most plentiful material is "secondary"metal—scrap jewelry, old dentures, factory wastes, residues fromelectroplating or engraving, and such like. These various ma-terials call for varying treatment, and the precious metals areseparated out and purified by a variety of chemical and metallurgi-cal processes, depending upon the metals present, the impuritiesinvolved, and the proportions in which they occur.

As the last stage in his procedure, the refiner usually convertssome or all of his pure metals into alloys—18-k gold, 14-k gold,sterling silver, iridio-platinum, rolled gold, dental alloys of variousformulas, and so on,—and shapes them into wire, sheet, tubing,or such other forms as are desired by the trades and arts.

LINKS IN OUR ECONOMY

It should be clear by now that the buying and refining of oldprecious metals are important links in the chain of our economy.They return to usefulness thousands of ounces of indispensablematerials that might otherwise be lost to humanity. Gold is morethan a trinket; for one thing it is a metallurgical necessity in dentalsurgery. Platinum is more than an item of luxury; it is an irre-placeable element in dozens of scientific applications of supremeimportance. Nor has Nature been generous in supplying us with

these metals; they are scarce and hard to find. Accordingly thecommunity owes respect and honor to the men who collect thesemetals—sometimes in forms that suggest neither beauty nor useful-ness—and return them to the refinery, whence they will emerge tobegin again the cycle of beauty and usefulness.

CHAPTER VI

Some Paragraphs for the ProspectorSooner or later any person—jeweler, refiner or gold buyer—who

can appraise old metals will be asked to appraise minerals andores. Nuggets that look like gold, and grains that might possiblybe native platinum, will be brought hopefully to his desk. Butwhile it is true that gold is gold wherever you find it, the fact re-mains that the identification and appraisal of ores call for differenttechniques from those described herein. While the tests and re-actions can be adapted for use with ores, the adaptation may bemodified considerably by the materials with which the nativemetals are combined or admixed. A man who is skilled in onetype of appraisal may find himself at a loss in the other type.

Such readers, therefore, as are interested in prospecting, areurged to study the excellent literature of this field, and to availthemselves of the help of our federal and state governments. Aperson who has already had experience in the tests described inthis book will quickly pick up the additional techniques.

SOURCES OF INFORMATION

Practically every state in the Union maintains a bureau thatpublishes authoritative information of interest to prospectors,miners, and others concerned with the development of our min-eral resources and industries. These bulletins usually are dis-tributed free of charge to residents of the state, and at cost to non-residents. For example, Field Tests for the Common Metals, byGeorge R. Fansett, is only one of the many useful publications ofthe Arizona Bureau of Mines. It gives tests for over thirty min-erals, including gold and silver (but not platinum), and may be ob-tained from the University of Arizona at Tucson. The price istwenty cents.

Most states also maintain laboratories for the identification ofminerals, and will reply to questions regarding probable markets.

This service is often supplied free if the specimens originate withinthe state; a small charge is made for samples submitted from out-side the state. When assays, quantitative chemical analyses, spec-trographic analyses, microscopic or thin sections are desired, theyare furnished at rates established by law.

Many schools and universities, especially in regions with impor-tant mineral industries, give instruction in mining engineeringand related subjects. For example, the University of Californiaat Berkeley gives a correspondence course in mineralogy, and sup-plies each student with specimens of ore for study and comparison.

The United States Bureau of Mines, although it does not dupli-cate the services rendered by state bureaus, is also glad to give ad-vice on prospective markets and otherwise to assist in bringing to-gether the buyers and sellers of mineral products. In addition ithas published much authoritative and intensely practical informa-tion of a general character, for example its Information Circular6148-R, entitled Selected Bibliography of Minerals and TheirIdentification. This pamphlet was prepared in answer to themany inquiries for the names of elementary books on geology,mineralogy, methods of identification, prospecting, and so on. Itgives short notes on the character of each book, the number ofpages, and the price.

M. W. von Bernewitz' Handbook for Prospectors is written forthe man in the field. It discusses grubstaking; the clothing andequipment needed; laws pertaining to mining; geology in pros-pecting; occurrence of ores; what minerals to look for and where;sampling; field tests and measurements; developing a prospect;markets and prices; and so on. It devotes almost two hundredpages to the occurrence, description, detection and uses of themetallic and non-metallic minerals, and it concludes with a glos-sary of terms used in mining. It is published by the McGraw-HillBook Company, Inc., of New York and London. It is only one ofthe many helpful publications mentioned in Bureau of Mines In-formation Circular 6148-R.

IT IS EASY TO RECOGNIZE GOLD

The student who avails himself of the above sources of informa-tion will learn that some tests are easy and sure. Thus native gold

is easily recognized because of its color, its heaviness, its high melt-ing point, its malleability, and certain chemical reactions withwhich the reader is now familiar. These facts, and descriptions ofthe minerals that are sometimes confused with gold, as well asmany other pertinent facts, are given in the literature, much ofwhich is in popular form and suitable for the man in the field.

PLATINUM NOT ALWAYS EASY

There is less popular information on native platinum-groupmetals. They are even rarer than gold, and found in fewer partsof the world, and while in some forms they are easily recognized,other forms are difficult to identify and even more difficult to ap-praise. Thus crude platinum in the form of easily recognizedmetallic grains is sometimes recovered from stream beds. In thefield we take advantage of platinum's high specific gravity and panthe sample. When an experienced man is handling the pan, theplatinum will hang back of the gold particles with which it is oftenassociated. The platinum grains are often of a silvery white colorthat could be confused only with silver, or perhaps with bits ofsteel, from which the reader of this book could at once distinguishthem by tests described herein. The presence of platinum shouldbe confirmed by the ammonium chloride reaction given in SectionC of Chapter IV. A hand lens will be an aid in examining theseheavy particles and will indicate to an experienced eye whetherit is worth while to send the sample to an assayer. The assay ofthe platinum-group metals is much more difficult than that of gold.Several scientific organizations, notably our National Bureau ofStandards, have done much to dispel the mystery that once sur-rounded these metals, but even so, many chemists still approachwithout pleasure the tedious task of determining and separatingthem.

On the other hand, the platinum metals are often found asminor constituents of ores of other metals, and in such small pro-portions that it is impossible to detect them in field tests. For ex-ample, let us consider one large source of palladium and platinum—the nickel-copper ores of the Sudbury District in Canada. Theplatinum content of these ores is little more than one part in twomillion. (Small amounts of rhodium and the other platinum

metals are also present, beside gold and silver.) Since large ton-nages of ore, over 1,800,000 tons in 1934, are treated for the recov-ery of the main products, generous amounts of the platinum metalsare obtained as by-products. In the treatment of these copper-nickel ores, the platinum metals become concentrated in the cop-per-nickel matte of the smelting process, then when the nickel iselectrolytically refined the platinum, palladium, rhodium, gold,silver and other metals are recovered as by-products. In 1938, 57percent of the world production of platinum-group metals was ob-tained as by-products of the refining of ores in which some othermetal—copper, nickel, gold, silver—was the main enterprise. Here,then, are ores of great commercial importance, but of so small aplatinum content that the tests used on old jewelry will not revealtheir value. What the prospector needs here is a knowledge ofpractical geology and mineralogy, to be confirmed by a laboratoryanalysis or assay.

"BLACK SANDS"

Another source of platinum that has been the subject of muchtalk is the so-called black sands that often accompany gold in al-luvial deposits. These sands are a mixture of heavy grains ofvarious minerals, including magnetite, chromite, ilmenite, cassi-terite, tourmaline and others, some of which are quite worthless.Occasionally the platinum grains are fairly easy to identify. TheUnited States Bureau of Mines in its Information Circular I C7000, dated March 1938, warns the public not to be too enthusi-astic over the chances of striking it rich, and explains that for overhalf a century much money, energy and time have been wasted onblack sands that generally were not worth the effort, partly becausethe total platinum content was low, partly because the stuff withwhich it was mixed was of a nature to make refining difficult andexpensive. Circular I C 7000 describes the occurrence of thesesands, machinery for grinding and concentrating them, and sug-gestions for marketing such sands as may really be of value. Themetals in these sands dissolve very slowly in aqua regia; time, heat,and patience are required. This should be remembered when-ever tests such as the ammonium chloride reaction, described inSection C of Chapter IV, are used to identify them.

SOME WORDS OF WARNING

Metals as valuable as those of the platinum group are bound toinspire dishonest men to dishonest deeds. Much money has beenlost by the public to fraudulent stock promotions involving so-called platinum mines that contained no platinum at all. Thereader should recall that most of our forty-eight states maintainlaboratories for the identification and assay of ores and minerals,as well as bureaus that supply information on the marketing ofsuch materials. These bureaus are at the command of any res-ident with legitimate need for their services, the prospective in-vestor as well as the mining prospector, and there is no need to gofar from home for information.

By the same token, the jeweler or old-gold buyer in Boston orBaltimore, for example, who receives a sackful of what looks likegold nuggets from some stranger in a far-off mining town will dowell to be curious. He may learn that the stranger is merely onewho fears to entrust his secret to any home town neighbor. Orperhaps he is a crank who has canvassed every testing laboratoryin his own region and will not believe what they tell him. Orthe situation may have a sinister aspect, for sometimes thestranger is a promotor angling for a statement, on the stationeryof a reputable firm, that his sample contains gold, the whole thingbeing merely a stock-selling scheme.

ONE MORE LINK

On the other hand, a jeweler doing business in a mining regionmay find it important to be able to handle mineral specimens. Ifhis neighbors trust his skill and integrity they will come to him inspite of the services offered by the government bureaus. And ifhe studies the available literature, and practises with samples ofknowns and unknowns, he will soon find himself with a useful andprofitable accomplishment—one with which he can forge one morelink in the chain of our precious metal economy.

APPENDIX

A.

A LIST OF EQUIPMENT

The following chemicals and equipment are mentioned inChapters I, II and IV. Not all readers will want all items.

Touchstone.Acid bottles.Standard yellow gold needles.File. Magnet.

Nitric acid.Hydrochloric acid.Table salt.Medicine droppers.

Samples of gold and other yellow metals of known composition.Standard needles of green gold and white gold.Samples of silver alloys of known composition.Samples of white base metals.Air-gas or oxygen-gas torch or blow-pipe.Potassium dichromate. Small glass rods.Sulphuric acid. Ferric chloride.Samples of platinum metals, gold, assorted alloys.Standard platinum testing needles.Spot plate. Dropping bottles.Small test tubes. Stannous chloride.Pure tin. Dimethyl glyoxime.Ammonia. Sodium thiosulphate—called "hypo."Tincture of iodine. Ferrous sulphate.Ammonium chloride or potassium chloride.

The chemicals are all common and inexpensive, and can befound in most drug-stores and camera shops, or in any chemicalsupply house. Not all readers will want all items. The touch-stone, acid bottles, and standard testing needles are sold by jewel-ers' supply houses.

The only articles in this list that might be unfamiliar are thespot plate and the dropping bottles. These are described as fol-lows in the catalogue of Eimer & Amend, dealers in laboratory

supplies, 633 Greenwich Street, New York, N. Y. Other dealershave access to this catalogue and can obtain similar articles.

Dropping bottles: Eimer & Amend catalogue number 3-000. Twosizes, 30 cc. or 60 cc.

Spot plate with cavities: Eimer & Amend catalogue number*3-745-5-

The standard platinum testing needles are sold by SigmundCohn, 44 Gold Street, New York, N. Y.

B.WHEN HANDLING STRONG ACIDS

Nitric acid, hydrochloric acid and sulphuric acid must be han-dled with care. They quickly attack the skin, clothing, wood andmetal surfaces, and so on. When working with them, be sure tohave close by plenty of water in which to wash your hands—run-ning water or a big basin. Provide yourself with old rags for wip-ing spilled acid from the table or floor, and burn them after use.

If you spill acid on your hands or clothing, the first thing to dois to wash it off immediately, using plenty of plain water. Afterthat it does no harm to neutralize with a little weak ammonia or

c.How To DETERMINE SPECIFIC GRAVITY

It takes only a few minutes to determine specific gravity, andthe equipment is simple—a good balance with weights; a piece ofthin thread; a cup of water and a support to hold it.

Method: First weigh the article as usual, writing down theweight. Next, weigh it while it is hanging in water; the weightwill be slightly less. Subtract the second weight from the first.The specific gravity will be the first weight divided by this differ-ence. To explain:

Most balances have a hook at the end of the beam where the panis hung; hang your object on this hook, using thin silk thread.Weigh the object, and call this weight Wa. Now fill a small cupwith water, and bring it up under the hanging object until thelatter is completely immersed. Many balances are accompaniedby a support for this purpose—it is shaped like an inverted U, justlarge enough to bestride the pan. You can make such a supportby bending a piece of sheet metal or cardboard.

Next, weigh the object while it hangs in the water. Call thisweight Ww. Find the difference between Wa and Ww and call it D.

Be sure to get rid of bubbles of air that may attach themselvesto your article; they will upset the reading.

This method applies to objects heavier than water. The tablegives the specific gravities of pure metals only, and alloys will bedifferent; for example the figure for 18-k green gold is about 15.8,more or less, depending upon the formula. 18-k yellow gold,about 15.1. 14-k yellow gold, about 13.2. 10-k yellow gold, about11.7. Sterling silver, about 10.4. Coin silver, 10.35.

bicarbonate of soda. Never attempt to neutralize until after youhave removed all acid possible with plain water.

This table shows the reactions of the commoner metals and theiralloys to cold, full-strength nitric acid; to cold full-strength hydro-chloric acid; and to the oxygen-gas flame. It is assumed that thesamples will be in the form of small articles—neither as a finely-divided powder nor a large mass.

Specific gravities are given in the usual units—water = 1.0—andmelting points are expressed in degrees Centigrade.

The small raised numerals refer to the following notes:

1. Iron, steel and chromium under concentrated nitric acid oftenremain "passive" or insoluble for some time. But if scratched,or touched with a wire of some dissimilar metal, they will beginto react with vigor.

2. Lead is readily soluble in warm nitric acid, especially if thelatter is diluted. It dissolves slowly in hot hydrochloric acid,but on cooling the white insoluble lead chloride precipitatesout.

3. Silver when treated with hot hydrochloric acid, or hot aquaregia, is slowly converted into the white insoluble silver chlo-ride.

4. Tin is converted by nitric acid into a white gelatinous solidcalled meta-stannic acid. It dissolves promptly in hot hy-drochloric acid; slowly in cold.

E.SOME DEFINITIONS AND FORMULAS

alloy. (1) A mixture, or combination, or solid solution, of two ormore metals, usually made by melting them together; as, brassis an alloy of copper and zinc. (2) The baser metal, or metals,combined with a finer one.

aluminum bronze. Alloy of copper and aluminum, having a colorresembling gold.

amalgam. Alloy in which one component is mercury.argent. French word for silver.argentan. French word for nickel-silver.Britannia metal. White alloy, originally made in England, contain-

ing tin, antimony, and some copper. Harder than pewter.bronze. Alloy whose principal components are copper and tin.cadmium. White metal, often added to solders to lower the melting

point and make them flow more easily.carat. A unit of weight for gem stones. Not to be confused with

karat, a term denoting the ratio of fine gold in an alloy. Theword probably comes from the Greek her at ion, a seed that wasused in ancient times as a unit of weight. Its value has variedfrom time to time. The metric carat is the standard now com-monly used, equivalent to 200 milligrams, or 3.08647 grainsTroy.

coin gold. U. S. A., 90 percent gold, 10 percent copper. GreatBritain, 91.66 percent gold, 8.33 percent copper.

cuivre. French word for copper.dwt. Abbreviation for pennyweight.electrum. (1) A native gold alloy, containing considerable silver.

(2) Nickel-silver.E.P.N.S. Abbreviation for "electro-plate on nickel-silver."E.P.W.M. Abbreviation for "electro-plate on white metal."fine. As applied to gold or silver, pure. Thus fine gold is pure 100

percent gold, without alloy.hard platinum. Pure platinum hardened by the addition of (usu-

ally) about 10 percent iridium; used in jewelry and other appli-cations where strength and resistance to abrasion are required.Other hardeners are sometimes used, 5 percent ruthenium beingone of the best.

invar. Alloy of 36 percent nickel and 64 percent iron, used inhorology because of its very low coefficient of expansion.

karat. A twenty-fourth part; a term used to express the ratio of finegold in an alloy. Thus, pure gold is 24 karats fine; see page 12for further examples. Should not be confused with carat, a unitof weight used for gem stones. Both words are probably derivedfrom the same Greek word, keration, meaning a seed used as aunit of weight. In the U. S. A. the form karat is used for the ratioof gold in an alloy, while carat denotes the unit of weight forprecious stones. Outside the U. S. A. the form carat, as well asother spellings, is used for both meanings.

lernel. Filings swept from a jeweler's workbench. They containparticles of precious metal mixed with dust, bits of solder, steelfrom the tools, and so on. From the French limaille, meaningfilings.

monel metal. An alloy containing about 65 percent nickel, 30 per-cent copper, and small amounts of iron and other metals.

muriatic acid. Another name for hydrochloric acid.noble metals. Metals that are permanent in air, showing no oxida-

tion under ordinary conditions. The Alchemists applied the termto gold and silver, which they believed to possess special virtues.The six metals of the platinum group have now been added tothis category.

oreide. Copper alloy of a golden color, containing some zinc andpossibly a little tin.

osmiridium. Naturally occurring alloy of osmium and iridium.The hard grains are used for tipping penpoints. Also callediridosmine.

pewter. Alloy formerly popular for household and table ware.Consists largely of tin, with copper and lead in varying propor-tions, with or without small amounts of zinc, antimony, and bis-muth.

pinchbeck. Alloy of about 88 percent copper and 12 percent zinc,having a reddish golden color. Used in cheap jewelry, etc.

pink gold. Gold alloy containing a fairly high proportion of cop-per, plus a little nickel, with or without zinc and silver.

precious metals. Metals which are prized because of physical andchemical properties that make them desirable for coinage or

INDEX

ACID bottles, 12Acids, when handling, 84Alkaline solutions, 60Ammonium chloride test, 59Antiques, 36Aqua regia, 14, 47

and gold, 14and silver, 21and stainless steel, 25and platinum metals, 46

Archimedes, 61Assay Offices, 69Assaying, 8, 72

BASE metals, 12,18, 24, 26,43, 86and stannous chloride, 51

"Black sands," 81Blow-pipe, oxy-gas, 44Bottles, acid, 12

dropping, 45, 47, 84

CHAINS, 35Chromium, 26, 27, 86Coin silver, 23Commercial standards, 31, 33Contact points, 27

DENSITY, 20, 61, 85Dental alloys, 16, 37, 73Dichromate test, 22, 25Dimethyl glyoxime solution, 53Dropping bottles, 45, 47, 84

ELECTROGRAPHIC tests, 60Enforcement of laws, 34Equipment for testing, 11, 45, 83

FACTORY wastes, 74Fansett, George R., 78Ferrous sulphate test, 58Field tests, 78File, 11, 35Filings, 74Flame test, 19, 26, 27, 43, 86Fraud, 36, 66

GERMAN silver, 25Gilchrist, Raleigh, 57Glow test, 58

Gold and aqua regia, 14and ferrous sulphate, 58and the flame, 20and nitric acid, 12and stannous chloride, 50buying and selling, 63, 66, 71rilled, 22, 25, 36, 71green, 15, 21native, 7g"on sterling," 22plated goods, 71price of, 70red, 16rolled, 22, 25, 36, 71white, 16, 28, 39, 40, 42yellow, 11, 13

Guilds, 29

HALL marks, 29Hydrochloric acid, 14, 25, 27, 84, 86

IODINE test, 58Iridium and iridio-platinum, 39, 40,

56, 57> 73"JEWELRY palladium," 41

KARAT, 12to determine, 13stamp, 29, 31

LAWS, stamping, 30, 32Lea, Carey, 57Licensing of gold handlers, 68Lydians, 7

MAGNET, 18, 43Melting points, 86Minerals, to identify, 78Mints, 67Molybdenum, 19, 26

NEEDLES for testing, 11,13, 15,42, 84Nickel, 16, 19

and dimethyl glyoxime, 54Nickel-silver, 25Nitric acid, 12, 84, 86

and gold, 12and silver, 20, 21and stainless steel, 19, 25and platinum metals, 26, 28, 46

OLD-GOLD industry, 65, 70, 74Ores, to appraise, 78Osmium, 39Oxygen-gas flame, 19, 26, 27, 43, 86

PALLADIUM, 16, 19, 28, 39, 41, 44, 86and dimethyl glyoxime, 54and the flame, 19, 44, 86and iodine, 58and nitric acid, 28, 46and stannous chloride, 50in jewelry, 41, 46in ores, 80

Platinum, 28, 39, 40, 86and ammonium chloride, 59and the flame, 19, 43, 86and iodine, 58and nitric acid, 28, 46and stannous chloride, 49, 54buying and selling, 69, 72group of metals, 39native, 80stamping laws, 32

Precautions, 35, 82Prospectors and prospecting, 78

QUALITY stamps, 29

REFINER, the professional, 67, 75, 76Refining precious metal wastes, 60, 75,

76Regulations, Government, 67Resistance alloys, 26Rhodium, 28, 39, 41, 46Ruthenium and its alloys, 39, 41, 46,

57Ruthenio-platinum and iridio-plati-

num, to distinguish between, 57

SCIENTIFIC apparatus, 37, 72Silver, alloys of, 23

and aqua regia, 21and dichromate, 22

and the flame, 19and nitric acid, 21brazing alloys, 24buying and selling, 69chloride, 21plated goods, 22, 70reactions of, 20, 86solders, 24sterling, 22, 23, 32

Solder, allowance for, 31Solutions, alkaline, 60

old, 59standard, 49

Specific gravity, 20, 61, 85, 86Spot plate, 45, 84"Spread" in prices, 70, 75Stamp of quality, 29Standard needles, 11, 13, 15, 42, 84Standards of quality, 30, 33, 34Stannous chloride solution, 48Steel, stainless, 19, 25Sulphuric acid, 26, 27, 84Sweeps, 74

TANTALUM, 19, 20, 26"Testing Solution A," 48"Tolerance," 31Touchstone, 7, 11, 13Trademarks, 30, 31, 35Troy weights, 64Tungsten, 19, 26

U. S. A. as gold buyer, 66U. S. Government Regulations, 67U. S. Bureau of Mines, 79U. S. Bureau of Standards, 32

VIGILANCE Committee, 34Von Bernewitz, M. W., 79

WARS, effects of, 40Wastes, factory, 74Weighing, 63