GLOXAM ON THE DETECTION OF BV.-On the Application of El'ectrolysis to the Detection of the Poisonous Metals in Mixtures containing Organic Mutters. By CHARLES 1,. BLOXAM. EVERYanalyst is oidy too well amitre of the difliculties which beset the detection of the poisonous metals in mixtures containing organic matters such as the contents of the stomach the solids and fluids of the body arid articles YJ€ food. The process which I belime most chemists now generally adopt in such cases consists in disintegrating and partly oxidising the organic matters by the aid of a mixture of hydrochloric acid and chlorate of' potmsa and afterrnards precipitating the filtered sof-ution by hydrosulphuric acid the arsenic acid having been previously reduced by means of sulphurous mid.In most cases the solutioii obtained by treatillg the organic POISONOUS METALS BY EEECTRO TAP SIS. matters with hydrochloric acid and chlorate of potassa affords n precipitate on the passage of hydrosulphuric acid whether any of the metals forming insoluble sulphides be present or not this precipitate is generally of a dark greyish brown colour; is very difficult to filter and wash; and interferes in a most disagreeable manner with the application of the tests for those metals which are precipitable by hydrosulphuric acid froni their acid solu+' "ions. It is therefore in the highest degree desirable to adopt some more satisfactory method for separating the nietals of the hydro- sulphuric acid group from orgaPric mixtures.Two of these metals arsenic and antimony may it is true be readily extracted in the form of gaseous hydrogen compounds by Marsh's process ; and the objections to this course haw been so often commented on that when I repeat some of the most im-portant of them here it is only that I may plead a fair excuse for submitting this communication to the society. The occasional prcsence of arsenic in the snlphuric acid and of both arsenic and antimony in the zinc has ahys been a serious objection to the use of Marsh's test; and although the hydrogen evolved at the beginning of the experiment may be carefully examined before introducing the suspected liquid the operator always proceeds upon the assumption that the zinc is perfectly homogeneous and that it is impossible for arsenic or antimony which had eluded detection in the first portion of hydrogen evolved to become apparent nhcn tlic rnms of the zinc has entered into solution.When liquids holding organic matters in solution are intro- duced into Marsh's apparatus the frothing occasioned by the viscidity of the mixture often gives rise to very serious inconve- nience; for although it may generally bc checked by the addition of alcohol itssometimes gets quite beyond the control of the operator and the experiment is entirely lost. But the most serious objection is that the liquid which has been examined by this method for arsenic and antimony cannot be ex-amined for any other metals on account of the presence of so large a quantity of sulphate of zinc a consideration of very grave importance in cases where the qnant$y.of the suspected matter is small. The ohjections to the convenient and delicate process of Reinsch rest upon similar grounds and are even more readily admissible. The deteetion of the poisonous metals by the decomposing action of the galvanic current is I think free from these objec- tions and so minute quantities of the poisonous metals may be detected by this method of testing that it may safely be relied upon in most cases of chernico-legal investigations.* The first experiments were directed to ascertain whether minute quantities of the most important poisonous metals could be easily detected by electrolysis in solutions free from organic matters Detection of Arseniic.The apparatus which was at first employed consisted of an ordinary U-tube one limb of which was closed with a perforated cork through which passed a tube for the escape of the hydrogen and a platinum wire connected with the zinc extremity of a Grove's battery of five cells; to this wire %asattached a platinum plate measuring ahout 2 inches by 9inch which was thrust down almost to the bottom of the U-tube. The other limb of this tube mas left open for the escape of the oxygen and contained a similar platinum plate connected with the platinum extremity of the battery. The tube which carried off the hydrogen was connected with a straight tube of hard glass drawn out to a long open point and heated to redness at the shoulder in order that any arseniuretted hydrogen might be decomposed in passing through it.At the commencenient of each experiment the U-tube was charged with a fluid ounce of diluted sulphuric acid (containing one measure of oil of vitriol and four measures of water) and as soon as the closed limb had become filled with hydrogen the drawn-out tube was heated with a spirit-lamp for 15 minutes in order to ascertain that no deposit of arsenic was obtained from the sulphuric acid alone. The solution to be examined for arsenic mas then introduced into the closed limb by withdrawing the cork for an instant and the experiment continued. The U-tube was immersed in a vessel of water to prevent the temperature from rising too high during the passage of the currc.n t .*Eefore submitting this communication to the So<Iiety the author was not aware of the existence of XI. Gaultier de Claubry's admirable paper upon this method (J. Pharm. [3],xviii 125; a6str. Chem. Soe. Qu. J. iii 162). This chemist hovrever appears lohave relied upon the precipitation of the arsenic not upon its evolution in the form of arseniuretted hydrogen. POISONOUS JXETALS BY ELECTBOLYSIS. The quantity of arsenic employed for each experiment was determined by carefully measuring out a standard solution of arsenious acid. Three expe iments made with aqwous solutions containing & & and T+m grain respectivcly (corresponding to W6 %076 and 90076 grain of mctwlIic arsenic) proved that the arsenic could be readily obtained as in Marsh’s test in the form of a brilliant metallic crust in the narrow point of the tube about half an inch beyond the heated portion.In order to ascertain whcther the presence of alcohol would interfere with the action of the test in case it might become necessary to add it in order to prevent frothing an ounce of dilute sulphuric acid and a drachm of alcohol were introduced into the apparatus and electrolpsed until the tubes were full of hydrogen ; on heating the evolution tube a faint odow resembling inercaptan was perceived but there was not the slightest deposit. Oil iiitro-ducing grn. of arsenious acid a most satisfactory mirror was formed in the tube in less than five minutes and a decidedly arsenical odour like that of alkarsin proceeded froin the extremity of the evolution tiibe.In subseqiient experiments as in this I found that the presence of alcohol appeared to facilitate the production of an arsenical crust and that the arsenical odour aflbrt’led a valuable confirmation with respect to the presence of arsenic. The method was then tested ax to its applicability in cases where the a&enious acid is mixed with large quantities of organic matters. A nlixture was prepared containing about 3. oz. lean meat 1oz. bread 1+oz. milk and 3 oz. white of egg beaten to a pretty uniform pulp in a mortar. To this mixture was added an aqueous solution of +&grain of arsenious acid. The whole was then mixed with 1 fluid oz. of hydrochloric acid and 4 08. of water; this mixture was digested in the water-bath for 15 minutes filtered and the clear solution evaporated on the water-bath to 3+ fluid oz.of a dark brown viscid liquid. On introducing one-fourth Df this (= 0.025 grn. .As03) into the decomposing tube it frothed up very much but was immediately checked by the addition of a draclim of alcohol and a deposit of arsenic was almost immediately formed in the heatcd tube. A repetition of the experiment gave a siinilsr result but about 15 minutes were required for the formation of a good arsenical mirror. BLOXAM ON THE DETECTION OF In a third trial one-sixth of the solution mas talien ( =0.017 grn. AsO,) with a like rcsult the odour of alkarsin being also very distinct. A fresh organic mixture was poisoned as before with & gm.of arsenious acid and treated in thc same manner being finally evaporated to 2 fluid oz. One-tenth of this opaque brown liquid (=0.01 grn. AsO,) gave a very distinct mirror in less than 5 mintites attended with a strong arsenical odour. One-hundredth of this liquid (= 0.001 grn. AsO,) also gave a very distinct mirror and dour in lo minutes. Since arsenic is sometimes contained in organic mixtures in a form (e.g. that of sulphide of arsenic) not readily soluble in hydro- chloric acid it became necessary to ascertain whether the solu- tion obtained by adding chlorate of potassa together with the acid would give the indication of arsenic by this method of testing for such a solution would of course contain the arsenic in the form of arsenic acid.The experiments made to determine this point proved that small quantities of arsenious acid (& gm.) could not be detected by this test after boiling with hydrochloric acid and chlorate of potassa unless the solution had been digested with sulphurous acid in order to reduce the arsenic acid The behaviour of tersulphide of arsenic was then examined. One-tenth grn. of arsenious acid was precipitated as sulphide the latter dissolved in hydrochloric acid and chlorate of potassa and the solution evaporated on the water-bath till the odour of chlorine was no longer perceptible. One-half of this liquid (= 0*85grn. AsO,) was introduced into the decomposing tube but no indication of arsenic was obtained in 15 minutes.The other half was saturated with sulphurous acid gas digested for some time in the water-bath and evaporated till the odour of sulphurous acid had disappeared. On subjecting it to the electro- lytic test a distinct mirror of arsenic was obtained in 10 minutes. One-tenth grn. of tersulphide of arsenic (= 0.06 gm. As) dissolved in diluted sulphide of ammonium was added to a mixture of articles of food similar to that previously used with the addi- tion of 3 oz. of strong ale. The mixture was digested on a water-bath with '4_ oz. of hydro-chloric acid and 3 02;. of water chlorate of potassa being added in small quantities until a thin homogeneous fluid was obtained; the POISONOUS METALS BY ELECTROLYSIS. 1’1 filtered liquid was digested for half an hour with a large excess of a saturated solution of sulphurous acid then evaporated on the water-bath to about oz.One half of this very nasty brown syrupy liquid mas mixed with a drachm of alcohol and introduced into the decomposing cell. The want of mobility in the liquid somewhat retarded the evolution of gas but in less than 15 minutes the arsenical deposit commenced and in 30 minutes a very beautiful mirror was obtained. In one or two of the experiments with orgnnic mixtures minute quantities of arsenic had escaped detection without any assignable cause; and I was therefore led to make some experi- ments to ascertain whether any influence was exerted by a varia-tion in the amount of hydrochloric acid present in the solution.A standard solution was prepared by dissolving 1 grn. of arsenious acid in 1000 grns. (by measure) of hydrochloric acid. 10 grns. of this solution (-& grn. AsO,) mixed with 20 gras. of hydrochloric acid gave a very distinct crystalline deposit of arsenious acid in the tube but no sublimate of metallic arsenic dthough a deposit of arsenic was formed upon the negative plate. 100 gms. of the solution (& gm. AsO,) mixed vith 200 grns. of hydrochloric acid gave a similar result. 50 grns. of the solution (Agrn. AsO3> diluted with 400 gms. of water behaved in the same way. In these cases the arseniuretted hydrogen appeared to have been converted into terchloride of arsenic which was decomposed by the aqueous vapour on passing the heated portion of the tube with formation of arsenious acid.Finding that in these experiments the smell of chlorine mas distinctly perceptible at the end of the evolution tube and believing that the chlorine disengaged at the positive pIate diffusing itself through the liquid caused the decomposition of the arseniuretted hydrogen I employed another apparatus consisting of two decomposing cells separated by a diaphragm of vegetable parchment. In this form of apparatus 10 grns. of the solution of arsenious acid in hydrochloric acid (= Thgrn. AsO,) mixed with 1%) grns. of hydrochloric acid and introduced into the negative cell of the apparatus (the latter having been charged as usual with a fluid ounce of dilute sulphuric acid) gave a beautiful mirror of arsenic in two minutes.VOb. XIII. c BLOXAN ON TRE DETECTION OF A mixture of articles of food to which -&grn. of arsenious acid had been added was digested with a fluid ounce of hydro-chloric acid and three or four ounces of water; the filtered solu- tion was evaporated down to one ounce upon the water-bath and one-tenth of it (= &grn. AsO,) was introduced into the apparatus with Q drm. alcohol. In less than fifteen minutes a very distinct arsenical mirror had been formed. The apparatus which was ultimately found most suitable for the detection of arsenic by electrolysis consisted of a two-ounce narrow-mouthed bottle the bottom of which had been cut off and replaced by a piece of' vegetable parchment tightly stretched over it and secured by a ligature of thin platinum wire (even vulca- uised caoutchone is speedily corroded) The bottle was furnished with a cork carrying a small tube bent at right angles and connected with the drawn-out reduction tube by a caoutchouc tube; through this cork passed a platinum wire bent into a hook inside the bottle for suspending the negative plate.The bottle was placed in a glass of such a size as to leave a small interval between the two and this glass was allowed to stand in n large vessel of cold water; an ounce of dilute sulphuric acid wa9 introduced into the apparatus so as to fill the bottle and the outer space to about the same level the positive plate being immersed in the acid contained in this outer space. When the bottle had become filled with hydrogen the shoulder of the reduction tube was heated to redness during fifteen minutes to ascertain the purity of the sulphuric acid and the liquid to be tested was intro-duced into the bottle by means of a pipette the cork being removed for an instant; n drachm of alcohol was afterwards introduced by the pipette to prevent frothing.In the following cases the arsenic mas most satisfactorily detected in this apparatus the evidence of its presence being three- fold and resting firstly upon the formation of the characteristic arsenical mirror; secondly upon that of a small shining ring of crystalline arsenious acid slightly in advance of the mirror ; and thirdly upon the development of the peculiar alliaceous odour. &grn.arsenious acid in hydrochloric solution. 1 -, aqueous solution. I0000 ,Y 1 I3T 9 dissolved in 120 gms. hydrochloric acid. 200 A 9 >> 115 , ?J 1 1000 1 IJ 120 9 91 and 240 grns. water POISOX'OUB METAL8 BY ELECTROLYSIS. These experiments were repeated with the same results. Experiments were then made upon organic mixtures containing arsenic which were boiled with hydrochloric acid and chlorate of potassa the arsenic acid being afterwards reduced to the arsenious by digesting with sulphurous acid or better with a few drops of a strong solution of bisulphite of soda. By this process TiT grn. and even -i-GT5 grn. of arsenious acid could be detected in an organic mixture with the greatest ease and certainty. If the sulphurous acid be not entirely expelled after the reduc- tion a little tersulphide of arsenic is deposited in advance of the metallic crust.The following process appeared to me the most trustworthy for the detection of minute quantities of arsenic in articles of food The solid matters are reduced to B pretty fine state of division mixed with enough water to form a thick grnel and digested in a a dish placed on a water-bath with about +oz. of hydrochloric acid for an hour powdered chlorate of potnssa being occasionally added as directed by Fresenius and von Babo until the organic matters are disintegrated when the liquid is filtered off and evaporated to about an ounce upon the water-bath. The browu fluid thus obtained is poured into a flask and a few drops of a strong solution of bisulphite of soda are added to it until it smells strongly of sulphurous acid; the flask is then heated in a water- bath until this odour has disappeared when the solution is mixed with at least an equal volume of water and introduced into the apparatus arranged and charged as above a little alcohol being poured upon the top.The operation should be continued for half an hour before the absence of arsenic is inferred. The advantages which appear to me to belong to this mode of testing are that it involves the use of a metal which has never been known to contain arsenic; that the very same portion of sulphuric acid which is employed throughout may be subjected to the test for any length of time before the suspected liquid is introduced ;that the evolution of gas is uniform throughout the experiment and is always so slow that no dread of losing the arsenic need assail the mind of the operator ;that the experiment may be interrupted for any length of time by breaking the contact with the battery without the least injury ;that the foulest liquids can be as readily tested as those which are perfectly clear ; c2 BLOXAM ON THE DETECTION OP and that the same portion may afterwards be further tested by any other process.The importance of this last consideration was fully exemplified in some of the early failures before I was well acquainted with the test for I always succeeded in detecting the arsenic in the same portion of the liquid by Marsh's test.It is evident moreover that this operation enables us to detect minute quantities of copper antimony mercury and bismuth if they be present in the solution. On considering the detection of the other poisonous metals in this way it is obvious that lead must be altogether excepted on account of the insolubility of its sulphate. Silver must also be omitted where hydrochloric acid is the solvent; and baryta of course would not be expected to answer. The remaining important poisonous metals antimony copper mercury bismuth and zinc were therefore tried bismuth being included on account of the medicinal use of its compounds. Detection of Antimony. 1 gm. of tartar-emetic (= 0.36 grn. Sb) dissolved in water was introduced into the decomposing cell.A mirror of antimony was formed just at each margin of the flame which heated the reduction tube and a copious deposit of antimony was formed on the negative plate. -& grn. of tartar-emetic (= 0.036 grn. Sb) gave only a slight wliite incrustation and no mirror in the reduction tube. The black deposit of antimony on the negative plate was dissolved by heating the Patter with a few drops of yellow sulphide of ammo-nium; on decomposing this solution with acetic acid a very distinct orange precipitate of tersulphide of antimony was obtained. A mixture of articles of food was mixed with -&grn. of tartar-emetic and treated exactly according to the process above described for the detection of arsenic. There was no appearance of a metallic deposit in the reduction tube in twenty minutes; but there was a thick coating of antimony upon the negative plate which was dissolved by yellow sulphide of ammonium.A portion of' this solution when evaporated in a watch-glass on the water-bath left a residue having a decided orange colour. A second and even a third coating of antimony was obtained POISONOUS METALS BY ELECTROLYSIS. by again immersing the plate for a few minutes and when the film was very slight it was at once identified by the orange stain produced when a drop of sulphide of ammonium was evaporated upon it. The result of the two last experiments which was fully con- firmed in all subsequent trials is a very important one its showing that minute quantities of antimony are not nearly so likely to be mistaken even for n time for arsenic in the electrolytic as in Marsh’s test and this seems attributable to the superior electro- positive tendency of antimony which ciisposes it to precipitate more readily upon the negative plate.In no case have ]I failed to detect antimony in this way. The following mode of proceeding may be recommended for the detection of the poisonous metals by electrolysis :-The mixture which may of course have been previously examined for organic poisons by the usual methods is digested on a water-bath with so much water hydrochloric acid and chlorate of potassa as may be required to disintegrate the solid portions and to render the liquid capable of filtration ; the filtrate is evaporated on the water-bath to a small bulk and digested in a flask with a sufficient quantity of solution of bisulphite of soda to impart a strong odour of sulphurous acid.The solution is heated in the water-bath until the odonr has disappeared and is once more concentrated if necessary by evaporation. It is then diluted with a volume of water equal to at least twice that of the hydro- chloric acid present and introduced into the decomposing cell enough alcohol being poured upon it to prevent any inconvenient frothing. The passage of the current having been continued for about an hour the negative plate is withdrawn washed and boiled in somewhat dilute yellow sulphide of animonium for a minute or two. This solution is then evaporated in a watch-glass placed on the water-bath and the orange residue of sulphide of antimony identified by the usual tests.The platinum plate having been again washed is boiled in a few drops of concentrated nitric acid to which a drop of dilute hydrochloric acid should be added to dissolve the sulphide of mercury. The acid solution is bofled down in the test tube to a small bulk and mixed qith an excess of ammonia when the presence of copper will be rendered evident and the teroxide of bismuth will be precipitated together with a little arnmonio- chloride of platinum. This precipitate when FRANKLAND ON THE COXPOSITION OF dissolved in liy drochloric acid evaporated and largely diluted will present the indication of bismuth. Tlie filtered ammoniacal liquid acidulated with hydrochloric acid and boiled with clean copper affords the usual evidence of the presence of mercury.Of the metals above mentioned mercury was found to be the only one which interferes with the detection of arsenic. If this metal be detected the liquid taken from the decomposing cell (or a fresh portion of the origiiial hydrochloric solution) may be distilled according to Dr. Odling’s recommendation in order to separate the arsenic from the mercury. The residue may still if the analyst deem it expedient be further dealt with by incineration or otherwise for the detection of other niekals.