August 15, 1943 A N A L Y T I C A L E D I T I O N 517

overcome by the formation of a complex of molybdenum with citric or tartaric acid.

(3) Ibid., 51, 3233 (1929). (4) Feigl, F., Z . anal. Chem., 74, 389 (1928). (5) Kolthoff, I. M.. Ibid., 70, 397 (1927). (6) Lancien, A., Compt. rend. , 144, 1434 (1907). (7) Petukhovrt, E. V., Zavodskaya Lab., 9, No. 1, 108 (1940). (8 ) Yagoda, H., and Fales, H. A., J . Am. Chem. SOC., 58, 1494 (1936).

PRE~ENTBD before the Division of Analytical and Micro Chemistry a t the 105th Meeting of the AMERICAN CHEMICAL SOCIETY, Detroit, Mich.

Literature Cited (1) Abegg, R., and Auerbach. F., “Handbuch der anorganischen

Chemie”, Vol. IV, Part 1, 11, p. 1018, Leipaig, S. Hirzel. 1921 (2) Barber, H. H., and Kolthoff, I. M., J. Am. Chem. Soc., 50, 1625

(1928).

Analvsis of Commercial Oil Emulsions and Wax Dispersions

FRANK M. BIFFEN AND FOSTER DEE SNELL Foster D. Snell, Inc., 305 Washington St., Brooklyn, N. Y.

Oil emulsions, which may or may not contain sus- pended solids, are analyzed by first distilling off any water-immiscible solvent. Benzene is then added and distilled with continuous return, carrying with i t the water which does not return to the sample. This avoids formation of troublesome emulsions during the conventional extractions of the oil phase. This procedure is sufficiently longer than the conventional extraction to be inadvisable for simple oil emulsions if they are readily extractable with ether. The aqueous distillate contains any alcohol. By centrifuging if necessary and evapora-

ETHODS of analysis of emulsions and suspensions as previously published (2) have been revised with

further experience to simplify the procedures and provide greater accuracy. One major change has been in methods ap- plied to oil emulsions, which may or may not contain sus- pended solids, to give more complete separation, avoid troublesome extractions in a separatory funnel, and prevent oxidation of the oils present. The importance of water-base wax suspensions has increased steadily and the types of soap stabilizers used have been complicated by commercial intro- duction of numerous amines. For brevity many conven- tional methods of analysis are referred t o only briefly without details.

Oil Emulsions The products in this class may vary from a medicinal oil

emulsion to automobile cleaner-polishes. Many of the prod- ucts contain fractions, such as petroleum naphtha, \+ hich are volatile mith steam. Glycerol is often present, alcohol occa- sionally. Some products contain from a trace to 2 per cent of waxes. The emulsifying agents encountered individually or as mixtures include 1 to 5 per cent of bentonite, varying with consistency and type of clay, usually less than 1 per cent of various gums, and surface-active agents, usually sul- fated oils or soaps. The latter are apt to be amine salts of fatty acids, but occasionally the other members of the class are present.

Persistence of soap and gum emulsions is a problem in con- ventional extractions which to a greater or lesser degree ex- tends to other surface-active agents. Of all the emulsifying agents mentioned, bentonite is the worst offender. Ether- n-ater emulsions stabilized with it will often not break even

tion of benzene, the oil is recovered without undue oxidation. The solid residue is then separated by conventional methods into alcohol-soluble, chloro- hydrocarbon-soluble, w-ater-soluble, and mineral fractions for separate analysis. Amine emulsifiers are determined on another portion of the original sample but all other determinations are carried out on the single sample.

Improved methods for analysis of water-base wax dispersions provide for precipitation by acid, fol- lowed by separation and approximate identification of resins, wax, amines, etc.

on prolonged centrifuging or on addition of minor amounts of alcohol ( I ) .

The method provides for first distilling any solvent volatile with steam, then adding benzene and distilling water with it. The oil, emulsifying agent, and abrasive, if any, remain in the flask in excess benzene and receive more conventional treatment. Only a single sample is required unless a nitrogen determination is required for estimation of amines.

Outline of Separation of Commercial Oil Emulsions

Original sample

SteLrn distillation - Immiscible solvent, water, alcohol

I Reflux nith henzene - Water, sometimes alcohol

I Centrifuge cold - Oils and bulfated oils in benzene solution

i Extract with hot alcohol - Glycerol. soap, fatty acid in alcohol

I

Extkact nith hot,C?H,Cl, - Waxes in C2H3C11

Exiract with hot water - TI-ater-soluble gums

RIikeral matter

Generally speaking, it is not necessary to use this method if the emulsion is of oil in water without added mineral mat-

518 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 15, No. 8

ter and the emulsion will break down readily with ether or petroleum ether.

FIGURE 1. DISTILLATION APPARATUS FOR USE IN ANALYSIS OF Ehrur.sroh-s

SEYARATION OF O m AND BENZENE-INSOLUBLE SOLIDS. The oils are now in hensene solution. Thoroughly agitate the con- tents of the flask to suspend the sediment and transfer to % 250- ml. centrifuge bottle. Rinse out the flask into the bottle with a few milliliters of benzene, and centrifuge the mixture. No water being present, a sharp separation occurs. Decant off the hen- Bene solution and add more warm heneene. Thoroughly break up the solids caked in the bottom of the bottle, shake vigorously to wash this with the benzene, and centrifuge. Repeat the process until the benzene extraot is colorless. Usually a total of three or four extractions is sufficient.

Combine the benzene extracts and evaporate carefully, 8. convenient technique being to collect the hensene in an empty Soxhlet tube. Evaporate the final residues of benzene on a water bath and dry the oils far a few minutes in an o v a , avoid- ing overheating with consequent oxidation or loss by evaporation. Cool and weigh the oils.

If saponifiable oils, castor or sulfated castor, for example, are pres- ent they will set,tle out as a viscous layer below the mineral oil. Chill the flask and contents, add chilled petroleum ether an the

OILS.

Allow the oil fraction to stand overnight in a desiccator.

petrolekm ether. Evaporate off th; petroleum ether from these flasks to obtain the mineral and saponifiahle oils separately. Analyze these in the usual manner.

Break up the residue in the centrifuge bottle and shake well with 75 ml. of warm 95 per cent alcohol is. I). 3A will do). Cool to room temperature and cen-

ALCOHOL-SOLUBLE MATTEU.

~~ ~~

~~~~~~~ ~~ I~

In case an alkali-metal soav was originally Dresent, which is

nresent ohecks hv ealcklation with the entire amount of alcohoi-

of this fraction. Evaporate the alcohol and proceed <,iCh tests on this.

If an amine soap nas originally present, it will usually have heen decomposed in the benzene distillation and subsequent ex- traction and drvinn. I n that cme an equivalent amount of

It will usunlly he glycerol.

fatty acid will he present. Take up the reGdue in warm alcohol and titrate to a phenolphthalein end point. Then evaporate to dryness, take up with vmrm water, acidify, and extract the fat,t,v acids with ether for identification If this does not check

I ~~ ~~

Gith the total residue. a senmation of rlyeeral as described in

August 15, 1943 A N A L Y T I C A L E D I T I O N 519

Centrifuge while still hot. Decant and repeat the process twice more. Evaporate the combined trichloroethylene extracts. Finally heat to constant weight at 110". Identify the extracted waxes by odor on burning, melting point. and other constants, if necessary. If the product is a polishing emulsion, it is probable that the was will be carnauba.

After extracting the waxes, drive off any excess trichloroethylene from the centrifuge bottle, first on a water bath and then in the oven. Add bo2ing water to the hot centrifuge bottle, break up the residue, and shake thoroughly. Centrifuge while hot and decant the solution of gums. Repeat the process at least twice mole, always using nater near the boiling point. Combine and evaporate the water extracts and obtain the water-soluble gums. I t is often convenient to dilute the extracts to a known volume and obtain total solids on an aliquot, te3ting for the type of gum present on a part or all of the balance. The most probable gums in order of decreasing im- portance are tragacanth, karaya, and acacia, but there are numerous other possibilities.

MITERAL MATTER. The residue in the centrifuge bottle is now matter insoluble in benzene, alcohol, trichloroethylene, and water. It will usually be mineral matter. commonly an abra- sive, bentonite, or both. Dry the bottle in the oven. conveni- ently overnight, cool, brush out, and weigh. Observe micro- scopically for the type of mineral present, or analyze chemically. A mesh analysis is often useful to classify the quality of an abra- sive. The absence of other emulsifying agents at earlier steps suggests the probable presence of bentonite at this point.

Determine nitrogen by the Kjeldahl method on an original sample and in the absence of other nitrogen compounds calculate to the amine suspected. For further details see wax dispersions belon-.

WITER-SOLCBLE GUMS.

AMINES.

Water-Base Wax Dispersions

The so-called no-rubbing floor waxes are the most widely distributed examples of this type of product. Rubber finishes, some shoe polishes, and several other types of prod- ucts are of similar composition. Owing to the complexity of these products and particularly to the extreme difficulty in separating added soap, soaps formed from resins present, resins of many types, and carnauba and other waxes, only approximate figures can be expected from an analysis of this type. Much knowledge of what to expect is needed, to se- cure reasonably accurate information.

Rapidly weigh 2 to 3 grams of the sample into a weighed porcelain capsule crucible approximately 5 cm. in diameter and 1 em. deep. steam bath for about 1 hour, and then in an oven at 105' to 110 for 3 hours. Cool and weigh. As the amines normally used in these products vary in rate of volatility, this size of sample, size of dish, and heating time are specified as a compromise found in practice to give best results.

Ash the nonvolatile matter in the same capsule over a low flame, taking care to ignite off all the carbonaceous matter. Cool and w-eigh. It is usually then desirable to ash the solids from about 20 grams of sample to provide a larger amount of ash. Dissolve the ash in water, dilute to 100 ml., and test qualitatively. If phosphate or carbonate is present, titrate an aliquot to phenol- phthalein and methyl orange end points. Determine any borax on an aliquot by titrating vith standard alkali to a phenol- phthalein end point in the presence of mannitol or neutral glycerol, applying a suitable correction for other alkaline salts. If other alkaline salts are present phosphate is best determined on another aliquot, using the volumetric molybdate method. Carbonate can be determined by the evolution method using another ashed sample, but is more commonly estimated from the total titration figure after subtracting the titrations equiva- lent to any borax or phosphate. Any substantial amount of sodium carbonate is usually derived from a soap used as sta- bilizer.

ACID-IYSOLUHLE ill ~ T T E R . Titrate a 100-gram sample, hot, to a methyl orange end point. This will give the total alkali in the sample. Add about 1 ml. of 0.5 S acid in excess and heat to clear the solution thoroughly. Allow to cool, when the waxes, resins, and fatty acids will separate as a waxy mass. Decant off the nater layer and wash the mass. If necessary, filter the mater layer and washings and collect in a calibrated flask. Reserve for further work.

Dissolve the waxy mass, including any on the filter paper, in 200 ml. of hot 95 per cent alcohol (S. D. 3A will do) Carefully boil the mixture to ensure complete disintegration,

TOTAL SOLIDS.

Heat the capsule and sample on

ASH.

Potassium soaps are rarely used for this purpose.

W A X E ~ .

transfer to a 250-ml. centrifuge bottle, and cool to room tempern- ture. Centrifuge until a clear upper layer is formed. If a semigel structure forms, add a large excess of alcohol and use two centrifuge bottles. Decant off the clear liquid, add more alcohol to the bottle, and bring to the boil in a water bath. Shake thoroughly, cool, and centrifuge as before. Decant and repeat the whole operation at least once or until the cold alcohol extract is colorless.

Add 100 ml. of trichloroethylene to the residue in the centri- fuge bottle and bring to a boil in a water bath. Shake well, and if any insoluble mat,ter is present, centrifuge while hot. Decant and wash the insoluble matter with small portions of hot tri- chloroethylene until the solvent is colorless, centrifuging if necessary. Evaporate the trichloroethylene extract and wash- ings. I t may be necessary to keep the extracted waxes in the oven at 105' to 110" for several hours before all the solvent is gone. After heating to constant weight, obtain such constants on the waxes as melting point, acid value, saponification value, and aniline point. Observe the odor on burning. Carnauba wax is most commonly employed but is frequently modified, for economy, with petroleum or mineral waxes. vegetable waxes such as candelilla and ouricury, and cumar-indene resins and poly- merized pine-type resins such as piccolyte. These will all dis- solve in hot trichloroethylene. If the character of this extract indicates a synthetic resin as well as waxes, boil it with 100 ml. of 95 per cent alcohol and centrifuge hot. Repeat at least twice more, being sure to keep the alcohol very hot. Cumar and piccolpte are insoluble in hot alcohol, whereas vegetable waxes are soluble in hot alcohol on repeated extraction.

Small portions of some natural reeins are soluble in trichloro- ethylene, and about 5 per cent of the natural mixture of waxes in carnauba wax is soluble in cold alcohol. Such small sources of error tend to counteract, each other, but, this error should be taken into account in interpreting results.

These are in the alcohol-soluble portion. There are no simple methods for separating the resins and the soap fatty acids. IIsually the soap in the original com- pound has been partially formed from the acidic portion of the resin and partially from added fatty acids or added as soap it- self.

Dilute the combined alcohol extracts to 500 ml.; on one ali- quot obtain total solid. and on other aliquots determine the acid value and saponification value. Test for rosin on the solids by the Liebermann-Storch reaction. Useful information as to colors obtained with various natural resins using the Lieber- mann-Storch reaction have been published (3). Notice the odor on burning and identify as rosin, copal, dammar, or other type of resin.

Any insoluble matter obtained after extracting the trichloro- ethylene-soluble is usually reainous and can be expected to be an alcohol-insoluble fraction of the original resin used. I t may be identified as was the alcohol-soluble portion.

Soaps of ammonia, mono-. di-, and triethanolamine, morpholine, aminometliylpropanol, and other amines are all used in water-base waxes as dispersing agents. Frequently only a guess can be made as to which is present. Experience indicates that some give off ammonia on heating with sodium hydroxide more readily than do others. With mixtures, such as are at times employed, the difficulty increases.

Dilute the aqueous portion, reserved after acidification, to 250 ml. and obtain total solids on an aliquot. The rate at which the solids lose weight is somewhat indicative of the type of amine present. Keep one aliquot in the oven, after evaporating off the bulk of the Oater on the steam bath for just sufficient time to be sure that all the water is removed. Cool and weigh. De- duct the weight of chloride equivalent to any fixed alkali found in the ash. The residual weight will be that of the hydro- chloride of the amine or mixture of amines.

On another aliquot. determine total nitrogen by the Kjeldahl method, calculate to the suspected amine, and further calculate to the hydrochloride of that amine. Thus, by trial and error calculations, a fair estimate of the type of amine, and also its amount. may usually be obtained. The interpretation of re- sults so obtained in the shape of a formula requires considerable practical experience and knoviledge both of the chemical and

cnl properties of the waxes, resinq, and amines, and of the cal properties they impart to the finished product.

Combine the alcohol extracts and reserve.

RESINS AXD FATTY ACIDS.

AMIKES.

Literature Cited (1) Biffen, F. 11.. Chem. Analyst, 20, 8 (1931). (2) Biffen, F. M.. and Snell, F. D., ISD. EKG. CHEM., ANAL. ED., 7,

(3) Mantell, C. L., Kopf. C. K., Curtis, J. L., and Rogers, E. M., "Technology of Natural Resins", pp. 441 et seq., New York, John Wiley & Sons, 1942.

316-19 (1936).