No. 388.

LONDON, SATURDAY, FEBRUARY 5.

MEDICAL JURISPRUDENCE.

PRACTICAL COMMENTARIES ON

DR. CHRISTISON’S PROCESSES

FOR

DETECTING POISONS.

NITRIC ACID—NITRATE OF POTASH-IODINE

-HYDRIODATE OF POTASH.

THOUGH the several subjects of the pre-sent paper have already been treated of atconsiderable length in some articles by Dr.0’alraugbnessy, published in the last vo-lume of THE LAKCET, yet, in order totender the present series complete, weshall present an ample abstract both of themethods of Dr. Christison, and of the im-provements upon those methods which havebeen suggested by Dr. O’Shaughnessy, ac-companied by some critical remarks, whichwe consider applicable to the whole.Dr. Christison thus describes the nitric

acid in its pure or diluted state, and the tests

by which it may be recognised :-" When concentrated, nitric acid is easily

known by the odour of its vapour, which ispeculiar. When pure, the acid, as well asits upour, is colourless ; when mixed withnitrous acid it is of various tints, and gene-raCy yellow or orange. The acid of com-merce is also at times rendered impure byEuipliuric acid, a circumstance which mustbe attended to in applying the subsequenttests. The simplest test for the nitric ornitrous acid is the action of copper, lead, ortin. If any of these metals in small frag-ments, or tin powder, be thrown into eitheracil previously diluted with an equal volumeo,r water, an effervescence takes place, whichin the case of lead or copper is much acce-!-;a’ed by heat; nitric oXIde gas is disen.gagel; and ruddy fumes of nitrous acid gasar firmed when the gas comes in contactwith the oxygen of the air. Many other

characteristic tests might be mentioned, butthe one described is amply sufficient. Inits diluted state it is not always so easilydiscovered as the other mineral acids, be-cause it does not form with bases anv inso-luble salt or precipitate. Professor Liebig,however, has lately discovered a very cha-racteristic and elegant test, provided theacid is not diluted with more than 400 partsof water. His test is taken from the effectof this acid on the sulphate of indigo. Asolution of indigo in sulphuric acid is to beadded to the suspected fluid till it commu-nicates a perceptible blue tint, care beingtaken not to make the tint too dark, parti- -

cularly when the suspected fluid is presumedto contain but little nitric acid. A drop ofsulphuric acid is next to be added, and themixture being put into a glass tube, heat isto be applied till it boils. A s soon as itreaches the point of ebullition the blue.colour is either discharged altogether, so.

that a colourless liquid forms, or it give%place to a faint straw-yellow tint. The lattereffect is remarked when the proportion ofnitric acid is small, and the indigo tintrather deep."On the preceding observations, and on

the value of the indigo solution as a test fornitric acid in small quantities, Dr. O’Shaugh-nessy commented at considerable length.When the nitric acid is in sufficient quan-tity, say ten drops, he believes the mode ofexamination by the metals recommended by-Dr. Christison to be entirely adequate, but:he denies that it is equally efficacious,when, as in the majority of cases, scarcelyso much as one drop of the pure acid canhe obtained. When so minute a quantity as.this only can be procured, it is perfectlyevident that no such examination can bemade. To remedy this defect, Dr. O’S. hasrecently proposed an entirely new re-agent,namely, morphine, which, when broughtinto contact with nitric acid, in the minut-est quantity, immediately produces a bril-liant vermilion colour. The mode of per.forming the experiment requires attention.

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A capillary tube should be used to absorbthe minute drop of suspected liquid, whichshould then be gently expelled on a parti-cle of morphine placed on a white porcelainsurface, when the characteristic tint is in-stantly produced.

Dr. O’S. has also satisfactorily shown, inhis first paper, that the evidence of the

sulphate of indigo is entirely fallacious ; as

chlorine, the chlorides, the chlorates, the

muriate of iron, muriatic acid, and manyother re-agents possess a similar decoloris-ing power. !We proceed to consider the means de-

. vised for the analysis of impure mixtures.Dr. Christison recommends that the acidfluid be neutralised with the carbonate of

potass, filtered and evaporated to crystal-lisation, that the crystals be heated withstrong sulphuric acid, in order to ascertainif nitrous fumes be evolved. "Sometimes,"Dr. Christison adds, " the nitrate of potass,when mixed with animal matters, will not

crystallise. On that account it will be pro-

per, when crystals are not formed, to eva-porate gently almost to dryness, and to treatthe residue with alcohol. The nitrate of

potass is thus dissolved, and so much of theanimal matter left behind, that the solutionis capable of crystallising." Again, in a

separate chapter he thus notices the chemi-cal properties of the nitrate of potass :" Its chemical properties are character-

istic ; it animates the combustion of burn-

ing fuel, yields nitrous fumes when heatedwith strong sulphuric acid, and in solutionis precipitated yellow by the chloride ofplatinum.* The salt of commerce containssome muriate of soda, and hence the odourdisengaged by sulphuric acid is often mixedwith that of chlorine or hydrochloric acidgas. If it is mixed with any vegetable oranimal infusion by which it is coloured, itwill be necessary, before applying these

tests, to destroy the colour with a streamof chlorine, to remove by filtration any floc-culent matter that may be formed, and then

’ to evaporate the solution till it crystallises. iIt will not always crystallise, however, whenmingled with vegetable or animal matters;but it may even then be known by the defla-gration which ensues on the residue of theevaporation being dried and heated nearlyto redness."In opposition to these remarks, Dr.

O’Shaughnessy asserts that the deflagration* This re-agent merely indicates the base, and

even on that does not act with any clelicacy.

is by no means sufficiently chanetetist!;,since the chlorates, bromates, oxalates, iodates, are similarly affected. He then pro-poses a modified, and, as he conceives, rr --

accurate method, for examining the of potash. To this we shall presently but we must previously mention a fallacy iiDr. Christison’s process which has the notice of our correspondent; Mm;", -,

that the nitrate of potassa is not soluble in

alcohol, and that white fumes are evolved

by the action of sulphuric acid on animalmatter alone. These fumes are sometimes

sulphurous acid ; more frequently an animalvapour, the nature of which we are not ableto determine.* It is true that Dr. Christisn

speaks of the examination of the crystals ;not of an amorphous mass; but it will rareiyhappen that crystals can be obtained so purethat they’will contain no organic matter, anuthe slightest particle is sufficient to invali.date the process by producing the sulphur.ous acid. The muriate of soda contained in

organic matter or food, will also frequentlycrystallise with the nitrate of potash, or

even by itself ; which affords another sourceof probable mistake.We have here also to recommend a moue

of filtration which we first adopted in experi-ments on nitric acid, and which has provedof such great utility that we have since em-ployed it in several analyses of another sort,It consists of an application of the sypbonprinciple, by folding lengthwise a shp ofbibulous white paper (about three inches

broad and eight long) into a plaited stripabout half an inch broad. One end of thisshould then be passed down to the bottomof the suspected mixture, and the other ex,tremity bent over into a receiving glass, whichshould be placed some inches below the

level of the glass containing the mixture foranalysis. The annexed wood-cut exempli-fies the apparatus ; a. the glass containingthe impure mixture ; b. the paper syphon:c. the receiving-vessel. The entire maybe covered with a bell-glass to prevent anyunnecessary evaporation.

* They are invariably associated with the o.i’ .<

principle of’ the substance acted on; thus. ’ -

evolves so characteristic a smell, that Mr. Bpretends to ascertain in this manner the

’

suspected sanguineous stams. No confidence,ever, should be reposed on such a procca, . the analyst be on a par with the Numidian hound in point of delicacy of smell.

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By this method an extreme degree ofp’ity is obtained in the filtered fluid. Its

or,ly disadvantage is the time consumed inthe filtering, which will be at least twenty-four hours for four ounces of fluid. Everyanechanical impurity must, it is evident, beentirely removed, because the fluid passesthrough at least 200 times the thickness offilter it would in the ordinary mode ; in fact,itis filtered through the length, not thethickness of the paper. In the case of thenitric acid its effects were decided by the

following comparative experiments :-sixounces of thick pea-soup were divided intotwo portions, and ten minims of nitric acidwere added to each; they were allowed tostand for twenty-four hours, and then

ascertained by litmus paper to be acid; bothwere then neutralised, and one thrown on an

ordinary filter; the paper syphon beingemployed with the other. In a few minutesa thick glutinous paste of farinaceous matterso beset the pores of the first that the liquidpassed through with extreme slowness, andthe filtration was not completed for twelvehours, In the second the filtration occupiedtwenty-six hours. The two liquids werevery different in point of transparency ; that

fiftered in the usual way being dark-brown,the other as limpid as distilled water. On

evaporation a further difference was soon per.ceived, the fluid of the first deposited flakesof vegetable matter, and could not be crys-t6’.!is?d; the second deposited no flakes andafforded several prisms as thick as needles,and an inch long.We must now cursorily notice the mode

in which Dr. O’Shaughnessy, in his first

paper, proposed to examine these crystals.!’ :tKcts a drachm of them to be introduceda very small retort with sulphuric acid,. installation to be performed, and the product,

nitric acid, to be condensed: a part of this isto be tried with morphia for the red colour; asecond to be boiled with alcohol and par-ticles of metallic silver, in order to obtainthe fulminating silver ; the third is to be

dropped into a concentrated solution of urea,which causes a precipitate of the nitrate ofurea.

In proposing these processes, it is evidentthat our correspondent fell into several, andby no means trivial errors. In the first

place, it is quite idle to talk of a drachm ofthe nitrate of potass, in cases where greatgood fortune will scarcely supply the analystwith one-tenth of that quantity ; secondly,the silver test is certainly inapplicable, be-cause the nitrate of potash must always inthese cases contain muriate of soda, and mu-riatic acid gas must, therefore, be disengagedalong with the nitric, in Dr. O’Shaughnessy’sprocess of distillation. A chloride of silverwill consequently be precipitated, whichwill inevitably preclude the formation of aparticle of the fulminating cyanate; more-over, the process is extremely difficult of

performance, even with the purest materials.We think also, that wherever a drachm o!nitre could be obtained, it would yielc’enough of nitric acid to show its decomposition by the metals, and the production othe brown nitrous acid fumes, which is 01course the best evidence of the entire

Lastly, we do not place any confidence inthe indications of the urea, for this reason,that the precipitation is apt to be preventedby muriatic acid, which we have alreadyshown will usually be present.We are, however, indebted to Dr.

O’Shaughnessy for a much more complete-a perfectly satisfactory method, described inhis account of the analysis of a suspectedstain in our 364th Number. We quote the

description, as we consider it perfectly un-exceptionable, and a curious specimen oi

the analysis of almost inconceivably minutEquantities of matter. Coupled with the modeof syphon filtering, we conceive this processto be amply adequate for the most compli-cated cases, for there is certainly no salt yetknown which acts in the same way on mor-

phine." The fragment of cloth was about an inch

square, and was unaltered in colour roundthe margin of the corrosions ; on beingmoistened with distilled water, it tasted

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acid, -and reddened litmus paper; it was.then agitated in a stoppered phial, with ijof distilled water, and a solution’of caustic

potash added, till litmus paper was no longerreddened. Three drops of this solutionvvere then placed on a bit of glass, apartfrom each other; one was touched with athin glass rod moistened with the nitrate ofbarytes, the second with the nitrate of silver;DO precipitate took place in either instance,and thus the absence of sulphuric and muri-atic acids or their salts was satisfactorilyproved. _ _

’ After filtering the solution through a

small glass funnel, the throat of which wasobstructed by a pellet of lint, it was then

evaporated to dryness on a watch crystal,when a white saline crust remained, whichweighed 1 of a grain. The lint, when driedand touched with a lighted taper, burnt

slowly like match paper or moxa, indicating.that the salt which passed through it in so-lution, was either a chlorate or nitrate ofpotash. To determine this point, the salineresidue was carefully scraped together, andplaced in a minute drop of pure diluted

sulphuric acid on a fragment of white porce-lain ; on dropping a particle of morphia intothis, a brilliant vermilion stain was imme.diately produced, which afforded a beautifulcontrast with the pale surface of the porce-lain beneath. Decisive proof was thus af-forded of the corrosions having been pro-duced by nitric acid. The rationale of the lastexperiment, however, requires explanation :on placing the particle of nitrate of potashin the dilute sulphuric acid, sulphate of

potash is formed, and nitrous acid expelled,- which immediately produces its beautifuland characteristic effect on the morphia.In repeating this experiment, it is also es-

sentially necessary to use white porcelain,since it is not acted on by the dilute sulphu-ric acid, and the production of the vermi-lion stain is thus rendered much more

striking than it could be by any other modeof proceeding."

The same remarks may be readily appliedto poisoning by the nitrate of potass itself. It3nust be remembered, however, that in caseswhere putrefaction has taken place, evidencemust be given with great circumspection, asnitric acid is invariably formed by the de.composition of animal matter. To conclude

our notice of the nitric acid. If only thesmall quantity of nitrate of potass describedby Dr. O’Shaughnessy can be procured, stillthe analyst may rest satisfied with the indi-cations afforded by morphine, coupled withthe deflagration of the filter-paper or lint.In the case of stains it would be wrong touse the syphon.filter. Finally, if a large

quantity of nitre be obtained, it may be de-

compoaed by sulphuric acid in a small re’;",and the product condensed, and treated witha few particles of copper, when the rud:;fumes of nitrous acid will be disengaged,

IODINE AND THE HYDRIODATE OF POTASH

Iodine.&mdash;The hydriodic acid and the hydri-odate of potash are important poisons, anddeserve serious attention, although Dr. Chris-tison has passed over the first without propos.ing any method, by which it may be detected,and he treats of the last in far too super;.cial a manner. The characteristic chemical

property of iodine in the free state is, lbatit forms with a cold solution of starch a blue

compound, the iodine of starch, which, bvthe action of heat, is rendered transparentand colourless, and which, by a current ofsulphuretted hydrogen gas, is also Meaebut

and converted into hydriodic acid. This acidhas no effect upon starch, and with alkaliesit forms a class of neutral salts, the hydrio-dates, of which the most important is the

hydriodate of potass. This salt in solution

is capable of dissolving a considerable

quantity of free iodine, and thus forms anioduretted hydriodate. When an oxygenizedacid, such as the sulphuric, is added to it,iodine is set free, which may be detected bystarch. The hydriodates are decomposedby many neutral metallic solutions, viz,those of platinum, lead, silver, and mercury,an iodide of the metal being precipitatedThe iodide of platinum is soluble in etherand ammonia, and when evaporated to dry-

, ness, yields free iodine on the applicationOf heat.

Iodine, when taken into the alimeutarc ycanal, remains there but a very short time

in a free condition. If the poisoned aomalhave recently eaten bread, potatoes, or otheramylaceous matters, the iodine is almost

immediately converted into the iodide t!

starch, and this again is, by some inexplica-ble digestive process, transformed into the

hydriodic acid. So rapidly do these changestake place, that in one instance in which weadministered a drachm of solid iodine to a

dog, though vomiting took place in fifteen

minutes, yet not a trace of free iodine could:!be detected by starch in the rejecteJ teis, though hydriodic acid was found in

large quantities.

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Again, the hydriodic acid once formed, ismidiv eliminated through the several excre-tory ehannets. In forty minutes we havefound it in the urine, in which, in the dogjust alluded. to, it was detected occasionally;.r ;ire days; viz., on the first and second,and on the fourth and fifth, when he died.

Strange to say, though the same process1’35 p&egrave;rfofmed with every precaution on thethird day, it gave no indications whatever of::B compound of iodine. We found it, how-evtr, in the saliva, which was secreted in im-mense quantities on that day. After deathnot a trace existed in the contents of the ali-

mentary canal. It is also worth recording, thatin this instance and four others no trace of in-flammation existed in the intestines,with the

exception of a few ulcerations of the glandsof Pe)er and Brunner ; but the air-cells ofboth lungs were infiltrated with pus, andtueir substance was preternaturally soft.This case we consider of great practical

importance, as we have strong reason to be-lieve that it affords an exact parallel to thechemical facts to be attended to in the hu-man subject. We believe that whereverdeath occurs later than sixty hours after

poisoning by iodine, it will be sought invain in the alimentary canal, while it mayhre been readily detected during life inthe urine. One of the first chemical dutiesof the practitioner called to a suspected case

In Dr. Christison’s observations on theiodine poisons, these facts are entirely omit-ted as far as the analysis is concerned, and a

mode of detecting the hydriodates is pro-poled, which would inevitably lead to totalfailure if applied to any complicated mineralfluid, such as the urinary excretion. Weshall not, therefore, transfer it to our

colomns, but proceed to detail the processwhich Dr. O’Shaughnessy has proposed, andwhich we have had repeated opportunitiesof examining since his paper was publishedin this Journal.He sets out in his chemical examination,

on the supposition that some combination ofhas been taken. In order therefore

t ,,;certain whether any free iodine is pre-sent, the contents of the alimentary canal:r: triturated with a little cold solution ofstarch, which would immediately cause the

mixture to assume a blue colour. If the

blue colour appear, the mixture is, if ne

cessary, diluted with water, and exposed to’a current of sulphuretted hydrogen, by whichthe iodide of starch is decolorised and con-verted into hydriodic acid. If no blue colourhave been produced, the mixture is merelyboiled with water and filtered. If the filter-ed fluid redden litmus paper, it should beneutralised with caustic potassa, and then.reacidulated with acetic acid. He next addsthe solution of the chloride of platinum.which, with the most minute quantities oChydriodic acid, either causes a dark-red pre-cipitate, or changes the fluid to a port-winecolour. It is then to be agitated with anounce of ether, which dissolves the iodideof platinum, and separates it from the otherfluids swimming on their surface, from,which it may be removed by a suction tube.The ethereal solution is, finally, to be eva-porated to dryness, and the iodide of plati-num heated by the spirit-lamp flame in a.small glass tube, when the iodine is disen-gaged in its characteristic violet vapour,and condenses on the sides of the tube indark dendritic crystals.The above process we have found to be

extremely delicate and easy of execution. Itis especially applicable to the urine or saliva.Occasionally in the urine, the simple addition of cold solution of starch and sulphuric:acid will strike the peculiar blue colour,which may be considered sufficient evi-dence. This experiment, however, is byno means so delicate as that just detailed.and it is, moreover, exceedingly liable ta beinterfered with by the animal matters whichthe urine contains.

REGENERATION OF THE LENS.

SOME years ago, MM. Cocteau and Leroyd’Etiolle published in Magendie’s Journal a ,

series of experiments, from which they weraled to suppose that the lens, after havingbeen extracted, is reproduced. The follow-

ing is a brief account of these experiments.The extraction of the lens was alwaysmade on both eyes by an incision at the up-per part of the cornea, and was generallyattended by prolapsus of the iris, and fol-lowed by violent inflammation.

First Experiment.&mdash;This was made on arabbit three months old. The lens could