Arsenites

True arsenious acid (HAsO 2 ) has never been obtained in a satisfactory condition, but its salts are readily obtained by di olving arsenious anhydride in a solution of the base, or by double decomposition. They are generally white, nearly all insoluble, except those of the alkalies, and all soluble in acids. Tests, Detec., . Owing to the importance of the subject, and for convenience and facility of reference, the leading tests for the arsenites and arsenious anhydride are noticed alphabetically below; to which a few general remarks on their application, under the various circumstances that occur to the chemist and toxicologist, are appended. When not otherwise stated, it is to be understood that they are to be applied to pure, or nearly pure and colourle solutions of arsenious acid or the arsenites. Ammonio-nitrate of silver gives a well-marked yellow precipitate of arsenite of silver in an aqueous or arsenious anhydride solution which is soluble in ammonia and in dilute nitric acid. Crystallisation Test. —A very minute quantity of arsenious acid placed in a small tube (arsenic-tube), and heated in the flame of a spirit lamp, gives a crystalline sublimate, which collects on the cooler portion of the tube, and which, when examined by a pocket lens, is found to consist of sparkling octahedral crystals (see engr. ) IMG:596405606043057898_i203-2.png: (Magnified.) Ellis’s Test. —This is a modification of the ‘nascent hydrogen test,’ in which the suspected gas is pa ed through a tube containing slips of copper leaf or riband, or still better pure oxide of copper, gently heated; the end of the tube communicating with the atmosphere being drawn to a capillary size, at which the gas may be inflamed and tested, as in ‘Marsh’s Apparatus.’ (See engr. ) If arsenic be abundant in the gas, the copper will be almost instantly covered over with a coating of metallic arsenic; and after continuing the heat for a few minutes it will present a beautiful silvery surface, and may then be submitted to further examination. IMG:596405606043057898_i203-3.png: a , Flask containing the suspected fluid, dilute sulphuric acid, and zinc. b , Funnel. c , Tube containing the copper-leaf or c.-riband, and heated by the lamp d . e , Support. f , Capillary end of tube c , with the gas inflamed. La aigne’s Test. (Adopted by the French Academy.) This consists in pa ing the gas generated in the suspected liquid, through a solution of nitrate of silver. (See engr. ) When arsenic is present black flocculi of metallic silver are deposited, and arsenious acid remains in solution mixed with nitric acid and some arsenide of silver. The filtered liquor, treated with ammonia, will now give a characteristic yellow precipitate of arsenite of silver; or a little dilute hydrochloric acid may be cautiously added to precipitate any remaining nitrate of silver, and the liquid, after filtration, tested for arsenic either in a Marsh’s apparatus, or with any of the liquid tests; or it may be evaporated to dryne , when its arsenious acid will be converted into arsenic acid by the nitric acid present, and will then be found to give the usual brick-red precipitate of arseniate of silver with a solution of the nitrate of that metal. See Marsh’s Test . IMG:596405606043057898_i204-1.png: a , Bottle containing dilute sulphuric acid, zinc, and suspected fluid. b , Funnel for supplying the bottle with acid. c , c , Supports. d , Tube filled with asbestos. e , Bent tube to convey the liberated gas. f , Gla ve el containing a solution of nitrate of silver. Marsh’s Test. Some of the suspected liquid is mixed with dilute sulphuric acid until strongly acid, and is then poured upon some pure granulated zinc, or clippings or other small pieces of zinc, previously placed in the apparatus; hydrogen gas is immediately evolved, and, if arsenic be present, unites with it, forming arseniuretted hydrogen gas, which escapes by the aperture b (see engr. ), and may be recognised as follows:— It po e es a garlic-like odour. It burns with a bluish-white flame and emits a whitish smoke. IMG:596405606043057898_i204-2.png: a , a , Bent gla tube, containing dilute sulphuric acid, zinc, and suspected liquid. b , Stop-cock and jet. c , Plate of gla to receive the stain. d , Support. e , e , Bands to keep the tube upright. If a piece of window-gla , or a white porcelain plate or saucer, be held a short distance above the flame, a fine pulverulent film of arsenious acid is deposited on it. See (fig.) above . If the cold plate be held in the flame, so as to slightly impede the combustion of the gas, a blackish-brown deposit of metallic arsenic is obtained, more or le deep, brilliant, and glistening. Both these deposits may be obtained simultaneously by holding nearly vertically over the flame a gla tube about 8 or 10 inches long and 3 ⁄ 8 ths of an inch in diameter. See (fig.) above . A solution of arsenious acid may be obtained by letting the flame play upon 3 or 4 drops of water placed on the under side of the piece of gla or china, to which the liquid tests may be then applied. Another plan is to apply drops of the liquid tests to the plate as above, and to let the flame play on them succe ively. The true arsenical spot or film is of a blackish-brown colour, and generally of a very deep hair-brown, usually surrounded at the circumference, with a white film of arsenious acid; whilst that of antimony, which in some points is similar, is of a deep black colour, and but feebly lustrous, and, when viewed by transmitted light, appears smoky black; whereas an arsenical spot viewed in the same way appears brown. It is further distinguished from others by—Treated with concentrated nitric acid, it instantly disappears, leaving upon the surface of the liquid traces of the metal, which only di olve on the application of heat. This solution, gently and carefully heated, leaves a white residuum, which, when cold, gives with a concentrated solution of nitrate of silver a dull-red precipitate of arseniate of silver.—The nitric solution treated with a few drops of sulphurous acid, and subsequently with sulphuretted hydrogen, gives a canary-yellow precipitate of trisulphide of arsenic, which readily redi olves, forming a colourle solution with ammonia.—The arsenical spot, when heated, is turned bright yellow by sulphuretted hydrogen, and is then readily di olved, as before, by ammonia, and by its bicarbonate; whereas one of antimony is turned of a deep orange-red, or reddish-brown, by sulphuretted hydrogen, is not readily di olved by ammonia, and is scarcely or not at all affected by bicarbonate of ammonia.—It is freely soluble in and removed by hypochlorite of soda; a reagent which does not affect antimonial spots. Heated by a flame of pure hydrogen an arsenical stain rapidly disappears. A mixed stain of antimony and arsenic does not disappear by the action of the last two reagents, and is shown to contain arsenic by the two first tests above. When hydrochloric acid is present zinc stains are sometimes formed, but they do not resemble those from arsenic. The flame which produces it is very pale blue or bluish-white; whereas antimoniuretted hydrogen burns with a pale green or greenish-yellow flame, and a white smoke, both of which are characteristic. IMG:596405606043057898_i205-1.png: Obs. Marsh’s test is admirable for its simplicity, delicacy, and trustworthine , as well as for the ease of its application. It is adapted to all liquids, whether colourle or coloured, which are not so glutinous as to inconveniently froth during the extrication of the hydrogen. [79] Various modifications of the original apparatus have been proposed to obviate this difficulty; among which the one chiefly deserving notice is figured in the margin. It consists of a bent tube having two large bulbs blown in it, and fitted with a stop-cock and jet in the usual manner. In this case the grains or fragments of zinc are put into the lower bulb ( a ). It is, however, worthy of remark, that, with ordinary care and skill, a simple wide-mouthed bottle, furnished with a tube and cock, will often be found to answer quite as well as more costly apparatus; as the fluid is le liable to froth than in a narrow tube. Even a common quinine-phial, or a 4- oz. or 6- oz. medicine phial, fitted with a piece of gla tube of very small bore, or even with a piece of a common tobacco-pipe, for a burner (see engr. ), may be used when no more convenient instrument is at hand. [79] Animal ti ues and liquids containing organic matter are best prepared for testing for arsenic by Marsh’s test, in the following manner proposed by Odling:—The ti ue, or the residue obtained by the evaporation of a liquid over a water-bath, is to be thoroughly dried at a temperature of about 212° F., then ground to powder or cut up into small pieces, next drenched with the strongest hydrochloric acid and allowed to stand twenty-four hours in a warm place, and finally distilled. The distillate will contain arsenic (if it existed in the material under examination) comparatively free from organic matter, and is, therefore, in a fit state to be introduced into Marsh’s apparatus, as the organic matter, which is the cause of frothing, has been removed. IMG:596405606043057898_i205-2.png: A film of oil placed on the surface of the liquid tends considerably to le en the frothing. Objec., precau., . Objections have been raised to this mode of testing, from the great frothing which often occurs with organic mixtures, and from antimony and imperfectly charred organic matter also forming arsenic. But these objections are invalid, because there are easy means of purifying the liquid before testing it, and of discriminating between true arsenical spots or deposits and false ones. Another objection is, that both zinc and sulphuric acid sometimes contain arsenic; but to obviate this difficulty, we have only to use them when perfectly pure; and to test them by means of the apparatus before pouring the suspected liquid into it. Indeed, these objections apply with equal force to all those tests which depend on the production of nascent hydrogen. The precaution nece ary to succe , and to reliable results, is to set the apparatus with simple zinc, acid, and water, and after it has worked a short time to test the evolved gas for arsenic (as above); when, if no trace of that substance is detected, the suspected fluid, in which the organic matter (if nece ary) has been destroyed by any one of the methods hereinafter pointed out, may be added, and the operation continued. Care should also be taken not to light the jet of gas before all the atmospheric air is expelled from the apparatus, as without this precaution an explosion may take place. Modification of Marsh’s Test. — Davy. This proce consists in the use of sodium amalgam instead of zinc and sulphuric acid, both of which are liable to be contaminated with arsenic. Sodium, on the other hand, has never been found to contain arsenic, and mercury only very rarely; but should it exist in that metal, it can be easily removed by digesting the mercury in dilute nitric acid, and afterwards well washing it with water. One part by weight of sodium to 8 or 10 parts of mercury forms a very good amalgam. The mercury is placed in a test-tube, and the sodium gradually added in small portions; the metals readily combine, forming an alloy, liquid whilst hot, but hard and brittle when cold. The author uses this amalgam by placing the suspected solution, or solid substance, along with a little water in a test-tube, then adding a small piece of amalgam about the size of a grain of wheat, and quickly covering it with a piece of white filtering paper or the lid of a porcelain crucible moistened with a dilute solution of silver nitrate slightly acidified with nitric acid. If arsenic is present, a dull black or deep brown stain on the paper or porcelain will be developed on the moistened part, owing to the silver being reduced to the metallic state by the arseniuretted hydrogen. The solution may be made by di olving 20 gr. of nitrate of silver in an ounce of distilled water acidulated with 2 drops of strong nitric acid. It is advisable to place between the moistened paper or lid and the tube a small disc of bibulous paper, to prevent any particles of the liquid producing minute black spots, and thus interfering with the results. 1 ⁄ 1000 th part of a grain of arsenious acid in 1 c. c. of distilled water gives a very decided effect in a few moments, but much smaller quantities may be detected, e.g. , the 1 ⁄ 100000 th or even 1 ⁄ 1000000 th part of a grain in 1 c. c. This method is applicable not only to arsenic as arsenious acid, but also to other compounds of arsenic, soluble or insoluble in water, e.g. , orpiment and realgar, the alkaline arsenates, and even the metal itself if in powder. Organic matter interferes but very little with this method. Antimony, as in Marsh’s proce , will produce, with the sodium amalgam, results similar to those of arsenic; this, when brought into contact with the nitrate of silver, forms a black antimonide of that metal. Fleitmann, however, pointed out that antimoniuretted hydrogen is not evolved from strongly alkaline solution, and, as in this case, the action of the sodium amalgam is to render the mixture quickly alkaline, only a very small quantity of antimony present will be evolved, and by previously rendering the mixture strongly alkaline the evolution of that gas may be almost entirely prevented. It may be occasionally nece ary to determine whether the stains on the paper moistened by the silver solution are due to arsenic or antimony. It is then best to digest the paper-stain in sulphide of ammonium, the metal present being converted into a sulphide, and di olving in the exce of the alkaline salt, leaving the silver sulphide undi olved; the alkaline solution when evaporated will, in the case of arsenic, leave a bright yellow residue, almost insoluble in hydrochloric acid; whereas in the case of antimony an orange-coloured residue will remain soluble in that acid. Dr Ru ell observes that hydrogen alone is capable of reducing silver solution to the metallic state, but acknowledges that this action is exceedingly slow. Pellet, on the other hand, maintains that pure hydrogen when pa ed through solutions of soda and nitrate of silver has no action at the ordinary temperature; but he states that the silver salt which has been fused po e es an alkaline reaction in solution, and hydrogen thus produces a slight precipitate, which can be prevented by adding a drop or two of nitric acid. Davy, however, found in his experiments only the faintest po ible effect of the reducing action of pure hydrogen in solutions of caustic soda and nitrate of silver. Finally, the author mentions that where paper is used with the silver solution we must not forget that the silver alone will after some time blacken the paper, especially if exposed to light; but this gradual change antimoniuretted hydrogen. (‘Chem. News,’ xxxiii, 58-63.) Nascent Hydrogen Test. The apparatus used may be similar to that figured in the engr. The plan followed in the laboratory of Gie en is to heat the long tube through which the gas pa es to redne in several parts, to produce distinct metallic mirrors; and then to remove the tube from the hydrogen apparatus and transmit a very feeble stream of dry sulphuretted hydrogen through it, the metallic mirrors being at the same time heated by means of a common spirit lamp from the outer towards the inner border or extremity. If arsenic alone is present, yellow trisulphide of arsenic is formed within the tube; if antimony alone is present, an orange-red or black trisulphide of antimony is produced; and if the mirror consists of both metals, the two sulphides appear side by side, the sulphide of arsenic, as the more volatile, lying invariably before the sulphide of antimony. If dry hydrochloric acid gas be now transmitted through the tube, without application of heat, no alteration will take place if sulphide of arsenic alone is present, even though the gas be transmitted through the tube for a considerable time. If sulphide of antimony alone is present, this will entirely disappear; and if both sulphides are present, the sulphide of antimony will immediately volatilise, whilst the yellow sulphide of arsenic will remain. If a small quantity of ammonia be now introduced into the tube, the sulphide of arsenic is di olved, and may thus be readily distinguished from sulphur, which perhaps may have separated. IMG:596405606043057898_i206.png: a , Flask containing the suspected fluid, dilute sulphuric acid and zinc. b , Small tube, at the one end having an almost capillary orifice, where the gas is inflamed. c , Spirit-lamp. d , Support. Reduction Test. A small quantity of the suspected sample, in the state of powder, is mixed with twice its weight, or more, of some reducing agent or flux, and the mixture is placed at the bottom of a very small gla tube, and heated in the flame of a spirit lamp for some time, when the arsenic gradually sublimes, and condenses in the cooler portion of the tube, under the form of a metallic crust, mirror, or ring. A common test-tube, if of very small diameter, may be employed; but those known as the reduction tubes of Liebig, Rose, or Berzelius are undoubtedly the most convenient and efficient. (See engr. ) Liebig’s method is by using a mixture of equal parts of dry carbonate of sodium and cyanide of pota ium. The suspected substance, perfectly dry and in powder, being first introduced into a Berzelius’ tube, is then covered with 6 times the quantity of this mixture, and so that the whole will not more than half fill the bulb. A very gentle heat is next applied, to expel any adhering moisture from the powder and the tube, after which a strong heat is applied to the bulb, and continued for some time, to effect the entire reduction and sublimation of the arsenical compound. IMG:596405606043057898_i207.png: a , The arsenical mixture. b , Arsenical ring. The best fluxes to use are ferrocyanide of pota ium dried at 212° F., calcined bitartrate of pota ium, cyanide of pota ium, and powdered charcoal. The metallic ring is proved to be arsenical by the properties and tests previously noticed. Should it be imperfectly formed, or masked by decomposed organic matter, the portion of the tube which contains it may be cut off with a file, next coarsely powdered, then reintroduced into another arsenic tube, and the exposure to heat repeated. The characteristics most simple and well-marked are— The volatility of the deposit when heated, shown by its escaping from the hotter portion of the tube and condensing on the cooler part higher up or further on. Its conversion into minute octahedral crystals of arsenious anhydride, when repeatedly chased up and down the tube by the cautious application of the flame of a spirit lamp first to one part, and then to another. The character of these crystals with respect to volatility, lustre, transparency, and form, is so exceedingly well marked that a practised eye may safely identify them, though their weight should not exceed the 1 ⁄ 100 th or even the 1 ⁄ 250 th part of a grain. A pocket lens is here serviceable. The form of the crystals is very evident with a microscope of 4 powers. Oxide of antimony never forms octahedrons, but only prisms. In employing this test, particular care must be taken to avoid soiling the sides of the tube in inserting the mixture, and that the substances operated on are perfectly dry; as unle this is attended to, the experiment does not succeed. The common plan is to introduce the mixture through a small paper funnel or tube extemporised for the purpose. The heat at first should be gentle, and merely sufficient to expel any adhering moisture from the mixture and the inner surface of the tube; after which (except where otherwise ordered) the upper portion of the mixture should be strongly heated, and then the bulb or bottom of the tube exposed to the full flame. After the operation is complete the bulb or lower portion of the tube is usually removed by a file, and the portion containing the deposit hermetically sealed, when it may be preserved, unaltered, for any length of time, ready to be produced as evidence if required. This test is usually regarded as decisive; as we here actually obtain the arsenic in a solid form, recognisable by the most unequivocal characters. Reinsch’s Test; Cupro-arsenical Test. The suspected solution is strongly acidulated with hydrochloric acid (1 to 6 or 8), and after being raised to ebullition in a porcelain or gla ve el, a piece of bright and clean metallic copper about 1 ⁄ 2 inch long and 1 ⁄ 4 inch wide in the form of gauze or foil, but preferably the first, is added, and the whole boiled together. The time required for the ebullition varies according to the strength of the solution; when weak it should be continued for at least a quarter of an hour. When the quantity of arsenic in the suspected liquid is very small, at least half an hour should elapse before the removal of the copper. In solutions containing a notable quantity of arsenic, a few seconds is often sufficient to obtain a coating; but which, for safety sake, may be extended to two or three minutes, or even longer. Liquids rich in organic matter also require longer boiling than those nearly free from it. The coated copper, which has now acquired a characteristic iron-grey colour, is then taken from the liquid, carefully washed in distilled water, in alcohol, and (if greasy) in ether, next dried on blotting-paper, and then either cut into small pieces, or rolled into a small coil or cylinder. It is then heated in a reduction-tube over a spirit lamp, when the metallic arsenic forming the coating is volatilised, and yields a sublimate of minute octahedral crystals of arsenious anhydride; or, if the tube be very small, or any reducing agent be added, a bright metallic ring. When the coating on the copper is sufficiently thick, it may be scraped off with a knife, and heated separately in an arsenic-tube. This test is invaluable as affording a certain and ready means of abstracting arsenic from its solution, whether pure or mixed with organic matter. The contents of the stomach or other viscera may thus be at once examined, without any tedious preliminary operations. In this way Dr Christ is on discovered the presence of arsenic upwards of four months after interment; and we have ourselves found it two years and eight months after interment. The coated copper may be preserved unharmed for years. Dr Taylor found that the 1-8th of an inch in one of these deposits that had been kept in paper nearly fourteen years gave a well-marked ring of octahedral crystals when heated. IMG:596405606043057898_i208-1.png: Sulphuretted Hydrogen Test; Sulphur Test. This produces a bright yellow precipitate of trisulphide of arsenic (orpiment) in solutions containing a free acid; but acts slowly and imperfectly on pure and neutral solutions, and does not disturb those that po e an alkaline reaction. The suspected liquid should therefore be slightly acidulated with hydrochloric or acetic acid before applying this test, unle it be already acid, when it is better first to neutralise it with an alkali, and then to add the acid. The transmi ion of the gas through the liquid (see engr. ) should be continued for at least half an hour; when the end of the conducting tube, after being well rinsed in the liquid, is removed, and the gla , lightly covered with a piece of porous paper, set aside in a temperature of about 100° Fahr., until the odour of sulphuretted hydrogen is completely lost. The precipitate is now collected on a small filter, washed with pure water, and dried by a gentle heat. It is then placed in a watch-gla or small capsule, and redi olved in a little liquor of ammonia, which is then again expelled by heat; or it may be at once submitted to confirmatory tests. It is shown to contain arsenic by its ready and perfect solubility in ammonia, and in solutions of the fixed alkalies, their carbonates and bicarbonates, and in alkaline sulphides; by being nearly insoluble in hydrochloric acid, even when concentrated and boiling; and by yielding a metallic mirror when mixed with a flux and submitted to the reduction-test (which see ). Sulphuretted-hydrogen water and sulphydrate of ammonium act in a similar way to gaseous sulphuretted hydrogen; but much le effectively. IMG:596405606043057898_i208-2.png: For accuracy, the sulphuretted hydrogen should be washed by pa ing it through a small bottle containing a little pure water, or dilute sulphuric acid, before allowing it to enter the arsenical liquor. The reduction of the newly precipitated sulphide is generally regarded as the most important part of the investigation, and requires great care and attention. An extremely elegant and sensitive method of effecting this is by heating the mixture in a stream of dry carbonic acid gas. This method has been followed by Drs Babo and Fresenius with the most satisfactory results, and is thus performed:—( A ) is a capacious flask for the evolution of carbonic acid, half filled with rather large pieces of solid limestone or marble (not chalk). To one aperture of the doubly perforated cork, a funnel-tube ( a ) is adapted, which nearly reaches to the bottom of the ve el; to the other aperture a tube ( b ), by means of which the gas evolved is conducted into a flask of smaller size ( B ), in which it is washed and dried by concentrated sulphuric acid. The tube ( c ) conducts the carbonic acid into the reduction-tube ( C ), which is shortened in the engr. , and must be made of difficultly fusible gla . When the apparatus is prepared, the sulphide of arsenic intended for reduction is rubbed in a small basin, previously heated in a water-bath, with about twelve parts of a well-dried mixture consisting of 3 parts of dry carbonate of sodium and 1 part of cyanide of pota ium (prepared by Liebig’s method). The mixed powder is then placed on a small strip of card-paper beat into the shape of a gutter, which is next pushed into the reduction-tube up to the point ( f ), and the tube is turned half round. In this manner the mixture is deposited without soiling any other part of the tube; after which the strip of card-paper is cautiously withdrawn. The reduction-tube is then, by means of the cork ( e ), fixed in its place; a moderate stream of carbonic acid gas is evolved by pouring hydrochloric acid into the funnel-tube ( a ), and the mixture carefully dried, by very moderately heating the tube along its whole length, by means of a small spirit lamp. When the gas-stream has become so low that the bubbles pa through the sulphuric acid at intervals of about a second, the spot ( k ) is heated to redne by means of a spirit lamp. When this point is attained another strong spirit-flame is applied to the mixture, progre ing from ( d ) to ( f ), until all the arsenic is reduced and volatilised (the first flame at the same time continuing in action at ( k )). The reduced arsenic recondenses at the spot ( g ), forming a mirror, whilst an exceedingly small portion escapes at the capillary orifice ( h ), and fills the air with its garlic-like odour. The second spirit lamp is at last slowly advanced towards the other lamp, or the spot ( k ), so as to drive towards ( g ) all the arsenic which has adhered to the walls of the wider part of the tube. Both lamps are then removed, the tube closed at the point ( h ) by fusion, and heat applied, progre ing from the point ( h ) towards ( g ), to contract the mirror on that side also, which increases its beauty and distinctne . The tube is then cut off at ( f ), and hermetically closed and sealed. In this state it becomes a permanent evidence which may be referred to in any future proceedings. Neither sulphide of antimony nor any other compound of antimony yields a metallic mirror or ring when treated in this way. Le than 1 ⁄ 300 gr. of trisulphide of arsenic thus gives a very distinct and beautiful mirror; and even 1 ⁄ 500 gr. a clearly perceptible one. Voltaic Test. The wires from the opposite poles of a voltaic battery are immersed or brought in contact with a little of the arsenious solution placed in a capsule or on a piece of window gla . If arsenic be present it is developed at the negative pole; and if this be formed of copper wire, it becomes whitened and a umes the appearance of polished steel or silver, in consequence of the formation of arsenide of copper. Detection of Arsenic in Organic Mixtures. Of the tests those which act by producing coloured precipitates are only applicable, with any degree of certainty, to perfectly limpid and colourle liquors. Those depending on the extrication of arseniuretted hydrogen are partially free from this inconvenience; but even here, if the suspected liquid be more than slightly charged with organic matter, so much frothing ensues, as to render the proce nearly unmanageable. In this respect Reinsch’s Test po e es advantages over all others, as it may be applied even to coloured liquids containing a considerable quantity of organic matter, without these being subjected to any preliminary proce , and without danger of failure. In some cases also, as with liquids po e ing only a slight degree of consistency or colour, the arsenic may be separated, after simple filtration and acidulation with hydrochloric acid, by a stream of sulphuretted hydrogen, in the usual manner. The reduction-test is only applicable to solid arsenious acid, or to compounds of arsenic obtained by means of other tests or proce es. In toxicological examinations the poison is almost always to be sought for in mixtures loaded with organic matter, and under other conditions even more embarra ing. Soon after arsenic is swallowed it enters the circulation, contaminates the various ti ues, localises itself in certain viscera, and is eliminated in the excretions. Hence it becomes nece ary not only to examine the solids and liquids in which it is suspected the poison has been administered, the vomited matter, and the contents of the stomach and primæ viæ, but also, in fatal cases, the stomach itself, the liver, blood, muscles, and more especially the urine. [80] In such cases the stomach is the part first laid open, and a careful examination is made of its contents and coats in order to detect any undi olved particles of the poison, a pocket lens being employed, if nece ary, in the search. If any particles, however minute, are found they are carefully collected and submitted to the reduction-test. If the reverse be the case, the stomach (cut into small pieces), together with its contents, is submitted to some further proce , to obtain a solution suitable for the application of the usual tests. The liver, also some muscle, and any other portion of the body that may be selected, are likewise separately treated in the same manner. We have here both solid and liquid organic matter to operate on, and the problem for solution is the abstraction of their arsenic in the simplest and most certain manner, and in a form in which its presence may be demonstrated by tests. This subject has long engaged the attention of the most eminent chemists and toxicologists, and various plans have been proposed for the purpose, among which the following appear to be the most valuable and that usually adopted:— [80] Absorbed arsenic more particularly localises itself in the liver, in which it may generally be found in from 12 to 15 hours after administration. The liver also generally retains traces of arsenic long after it has been eliminated from the other viscera and the muscular ti ues. (Reinsch.) Solids (as the stomach, liver, .) are cut into small fragments and boiled in a gla ve el with water acidulated with about 1-4th of its volume of hydrochloric acid, until the ti ues or fragments are entirely broken down into flakes or grains, when the whole, after filtration, is again heated to the boiling-point, and tested as described under Reinsch’s test (see ANTIMONY ). Liquids do not require this preparation. Reinsch’s test is inapplicable when, as sometimes happens, the arsenic sought after may be in the state of one of the sulphides—either as orpiment or realgar—a not improbable contingency, when it is remembered that, although arsenious anhydride or white arsenic is the form most generally used for criminal or suicidal purposes, the yellow and the red varieties being largely employed in workshops where fireworks are manufactured, have not unfrequently been had recourse to. Again, when the examination of a corpse long buried and disinterred takes place, it must be borne in mind that the arsenious anhydride taken by the deceased has, by the decomposition of the body, become converted into sulphide. In these cases the hydrochloric acid nece ary for the performance of Reinsch’s test fails to effect the solution of the sulphide. Mr Blyth says: “It is found that the post-mortem change into orpiment is never quite complete, so that for the detection of arsenic in solid organic substances, such as the ti ues of the body, the best general method is most decidedly to convert the arsenic, if present, into the volatile chloride; and according to Dr Taylor, there is always sufficient arsenic (if present at all) unchanged into sulphide to ensure succe . The only nece ary caution is that the substance be thoroughly dried, and that the reagents be pure. After drying it is placed in a retort with fuming hydrochloric acid, and slowly distilled by the heat of a sand-bath. The distillate contains chloride of arsenic (if arsenic was present), and may be submitted to further tests.” Estim. This may be effected in various ways:— 1. Gravimetrically :—Arsenic is usually WEIGHED under the form of arsenate of lead, arsenate of sesquioxide of iron, tersulphide of arsenic, (metallic) arsenic, or (directly) as arsenious anhydride. The last three only, as the more simple and convenient, will be noticed here:— As trisulphide:—The whole of the arsenic being precipitated by a stream of sulphuretted hydrogen, with the nece ary precautions, in the manner already noticed, the precipitate, after being carefully collected, washed, and dried, is purified by redi olving it in pure ammonia water, and evaporating the resulting solution in a weighed watch gla or capsule by the heat of a water-bath. It is then dried at a temperature not above 212° Fahr., and finally weighed. Each grain of the tersulphide so found corresponds to ·80487 gr. of arsenious acid, or ·61 gr. of metallic arsenic. As (metallic) Arsenic:—Obtained by one of the proce es already given. Each gr. represents 1·32 gr. arsenious acid. As Arsenious anhydride:—Obtained in a weighed capsule or tube, either by the crystallisation or sublimation test. The weight is the answer sought for arsenious anhydride. Each gr. of this is equiv. to ·75758 gr. of metallic arsenic. Volumetrically. (Method of F. Mohr.) This depends on the fact that an aqueous solution of arsenious acid, or of an alkaline arsenite, when mixed with an exce of saturated solution of pure bicarbonate of soda and a little starch-paste, has its arsenious acid converted into arsenic acid by a solution of iodine. A standard solution of iodine is, therefore, an appropriate arsenim′eter for the above mixture. The solution of iodine is added until the blue starch-reaction just begins to appear, the arsenious solution having been previously exactly neutralised with pure carbonate of soda if acid, or with pure hydrochloric acid if alkaline. The results are accurate when no substance capable of oxidising or decomposing iodine is present in the liquid tested. Phys. eff., . Arsenious anhydride or white arsenic is alike destructive to vegetable and animal life. Seeds soaked in any but a very weak solution of it lose their power of germination, and buds plunged in it become incapable of expanding into flowers. When applied to the leaves, roots, or stems, absorption takes place, and the plant soon perishes. On combustion it evolves the characteristic garlic-like odour of arsenic, and arsenic may be discovered in its substance by chemical tests. According to Jäger, Gilgenkrantz, and Pereira, a few of the lower order of the algæ are occasionally developed in solutions of arsenious acid. To all animals, from the infusoria up to man, arsenic proves deleterious, although in different degrees, the highest susceptibility of its effects existing in man on account of the superiority of his development. In all of them death is preceded by inordinate actions and increased evacuations, especially from the mucous surfaces. Difficult respiration, thirst, vomiting, and convulsions are the leading symptoms which gradually develope themselves as we approach the higher grades of the system. (Jäger.) In very small or therapeutical doses, properly administered, it is a valuable medicine, and acts as a tonic, alterative, and antispasmodic attenuant, and externally as an escharotic. In slightly increased medicinal doses, or long-continued small doses, nausea, vomiting, purging, griping, debility, emaciation, and all the effects of slow-poisoning, occur in succe ion—a gradual sinking of the powers of life, without any violent symptom; a namele feeling of illne , failure of the strength, an aversion to food and drink, and to all the enjoyments of life. Redne of the conjunctiva and eyelids, headache and giddine , spasms, eczematous eruptions, numbne and paralysis of the limbs, and ptyalism, are also frequent and well-marked symptoms of slow poisoning by arsenic. In an exce ive or poisonous dose the symptoms are rapid and violent, usually indicating extreme gastro-intestinal inflammation and disorder of the cerebro-spinal system, and often occasioning death in from one to three days. The smallest fatal dose found recorded by Christ is on is 4 1 ⁄ 2 gr., taken in solution. The subject was a child 4 years old, and death occurred in six hours. 2 1 ⁄ 2 gr. destroyed a robust girl in 36 hours. (Letheby.) 2 gr., in solution, are suspected to have caused the death of a full-grown woman. 2 or 3 gr. may be a fatal dose. (Dr A. Taylor.) Notwithstanding these facts much larger quantities have been taken, under peculiar circumstances, with comparative impunity; and cases are not wanting in which even enormous quantities have produced very trifling effects. The dose for animals is — Cattle , 5 to 10 grains. Horse , 5 to 10 grains. Sheep , 1 to 2 grains. Pig , 1 ⁄ 2 to 2 grains. Dog , 1 ⁄ 15 th to 1 ⁄ 10 th of a grain. Under all circumstances arsenious anhydride is, undoubtedly, one of the most powerful of the mineral poisons; and in whatever form or way it is introduced into the system it exerts the same deleterious influence. In all cases, in sufficient doses, its action is to increase the secretions, diminish the contractility of the voluntary muscles, and to produce convulsions, prostration and death. Arsenic is a non-accumulative, irritant poison, and exerts no decided chemical or corrosive action on the ti ues. (Taylor.) Pois., .—Symp. These sometimes begin to appear within half an hour after the poison has been taken, or even sooner; but much more generally, not until after the lapse of some hours. They usually commence with nausea and distre at the stomach, followed by thirst, often intense, and a sense of burning heat in the bowels; then come on constriction of the œsophagus, violent vomiting, severe colic pains, tenesmus, and exce ive and painful purging, the stools being occasionally bloody; but pain, vomiting, ., do not invariably occur. The pulse is generally quick, small, feeble, and irregular—sometimes scarcely perceptible, and the heart’s action is irregular and tumultuous. The tongue is dry and furred; the respiration difficult and panting; the uri no-genital apparatus is often affected; there is pain and difficult micturition, and sometimes entire suppre ion of urine; faintings, coldne of the limbs, and cold sweats, with other signs of debility, intervene. Itching, and eczematous eruptions of the skin, trembling, painful cramps, and contractions of the extremities, and violent convulsions often follow; and after these, a greater or le prostration of strength, which induces a deceitful calm. At length the heart’s action abates, the skin becomes suffused with a cold clammy sweat, and the sufferer dies from exhaustion. The progre , succe ion, and precise character of the symptoms are modified by the idiosyncrasy of the individual, the quantity of the poison, and the manner in which it has been taken; and are seldom all present in the same person. Treatm. If vomiting has commenced it should be promoted by tickling the throat, and administering a large quantity of gelatinous hydrated peroxide of iron, or other appropriate antidote, in divided doses, mixed with a large quantity of warm or tepid water, strongly sweetened with sugar. If vomiting has not commenced, which is rare, it must be excited by administering 15 to 20 gr. of sulphate of zinc, or ipecacuanha (or in the absence of these, a teaspoonful of flour of mustard) in a tumbler of tepid water, and tickling the throat as before. If these means fail in rapidly inducing copious vomiting, the dose must be repeated, or the stomach-pump had recourse to. Altogether as much as 16 to 18 oz. of the hydrated peroxide of iron may be administered. If the poison has been swallowed several hours previously, and hence may have pa ed the pylorus, a strong dose of castor oil or a purgative clyster may be administered, and, after its action, another clyster containing the antidote. As soon as the stomach and bowels are cleared, diuretics and sudorifics should be given in abundance. Lastly, any remaining irritation must be relieved by demulcent and soothing remedies; or if urgent, by slight general or local bleeding, which cannot be earlier practised without danger; and opium, camphor, and ether, followed by tonics, may be had recourse to, to recruit the system. Lesions. Redne and inflammation of the whole primæ viæ; and sometimes of the mouth, fauces, and œsophagus, but more usually the contrary. Sometimes also, though seldom, there is no marked appearance of inflammation in the stomach and intestines. The stomach is usually highly injected, and frequently marked with extravasations; lungs gorged with blood; mucous lining of trachea reddened; heart generally flabby, and exhibiting deep red or blackish stains, and the right cavities more or le loaded with blood; the conjunctiva is sometimes very vascular; and redne , extravasation of blood, and effusion of serum is occasionally seen in the brain. The blood is frequently, though not invariably, fluid after death, and dark coloured. Under certain circumstances, the mucous membrane of the stomach and intestines is lined with a multitude of brilliant points or grains, which have been mistaken for arsenious anhydride; but which, according to Orfila, are composed of fat and albumen. Placed on burning coals, they decrepitate on drying, and produce a species of explosion or detonation. These grains are also met with in the stomach of persons who have not been poisoned. Digested in water, the liquid obtained from them does not show the presence of arsenic when submitted to reagents. Ant. In the order of their a umed efficiency:— Moist peroxide of Iron. —See under the preparations of Iron (Arsenic i Antidotum, G.). Hydrated or gelatinous sesquioxide or peroxide of iron (for an adult—a tablespoonful, in water, every 8 or 10 minutes until 12 or 16 oz., or more, have been taken). Hydrated sulphide of iron (as the last). Gelatinous hydrate of magnesia (as the last). Calcined magnesia (taken as the first). Salad or olive oil, or almond oil, and oil or fats generally (ad libitum), are all highly effective in le ening, if not destroying the action of arsenious anhydride. [81] Albumen (white of egg), or liquids containing it (in cold water, ad libitum). Milk, wheat-flour, oatmeal gruel (with water, ad libitum). Lime water, with milk (as the last). Chalk, with milk and water (as the last). Infusion or decoction of bark, or better, of nut-galls (as the last). Sugar or syrup (ad libitum). See Treatm. (above); also the above substances under their respective heads. [81] Dr Blond lot, in a paper communicated to the Paris Academy of Sciences, has come to the conclusion that the slightest quantity of greasy matter in contact with arsenious anhydride reduces its solubility to about 1-20th of what it was before. This explains at once why, in certain judicial investigations, arsenic has been sought for in vain in the liquid contents of the stomach, when the food consisted partly of fatty substances, such as broth, milk, . It likewise explains how arsenious anhydride, taken in powder, may sometimes remain a long time in the stomach before it produces any deleterious effect; since, in such cases, its action is hindered by the presence of fatty matter. Jugglers often swallow arsenic with impunity, because, according to Dr Blond lot, they previously take the precaution to drink milk and eat fat bacon. Hence, in cases of poisoning by arsenic, oils and fatty substances may be administered as real antidotes, capable of suspending the action of the poison for a considerable time, until more radical means of effecting a cure can be applied. The people engaged in some of the arsenic-works regard salad oil as almost a certain antidote to this poison. Uses, . Arsenious anhydride and its compounds are extensively employed in the arts and medicine. It is used by the dyer, it furnishes the artist with several of his most beautiful pigments, and the gla -maker and enameller with a flux or material to whiten and decolour their wares. In agriculture , it is used (in solution) as an anti-smut for seed-wheat; and as an anti-vermin lotion or dipping for sheep and cattle. In small (therapeutical) doses it is a valuable remedy in intermittent fevers, chronic skin diseases (especially lepra and psoriasis), and in several nervous affections (as neuralgia, epilepsy, chorea, tetanus, .). It is the active ingredient of the tastele ague-drop; of Fowler’s and Pearson’s solutions; and in the Tanjore pills, long celebrated in India for the cure of the bite of the cobra di capello and other venomous serpents, as well as of hydrophobia. It has been given in syphilis, chronic rheumatism, typhus, and several other diseases, with more or le advantage. Cautiously administered in phthisis, it frequently restores the appetite and strength and greatly retards, and in some cases arrests, the progre of the disease. It has been recently used to relieve toothache arising from caries. Externally, it is employed in the form of powder, lotion, and ointment, for the cure of cancer. Plunkett’s ointment, Pâte arsénicale, Davidson’s Remedy for Cancer, and several other like preparations, owe their activity to arsenious anhydride. Water in which white arsenic has been steeped has become a favorite cosmetic wash with many ladies, since its a umed property of softening the skin was announced in a certain popular periodical. It is also the prime ingredient in the papier moure, a popular fly paper. Its use, whether internal or external, is, however, attended with considerable danger in unskilful hands, and should, therefore, never be adopted but under proper advice.— Dose , 1 ⁄ 20 to 1 ⁄ 8 gr., made into pills with crum of bread and lump sugar; or in solution, 3 to 5 or 6 drops, twice or thrice daily, gradually and cautiously increased to 12, or even 15 drops. As a rule, arsenical preparations should be taken soon after a meal, and by no means on an empty stomach. (Dr A. T. Thomson.) The dose should be suspended, or greatly reduced, as soon as the conjunctiva is affected (Hunt); or if dryne of the mouth or throat, or irritation of the stomach or bowels, ensues. Mr Maculloch found the pills more efficacious than the solution; they act differently, and cannot be substituted for one another. Arsenic is a favorite tonic and alterative with farriers, who often administer it very carele ly to horses, to the serious injury of these animals. It is also a favorite with grooms, who have imbibed the notion that small doses of it contribute to improve the condition of the skin. The best-informed veterinarians, however, either wholly avoid it, or use it with very great caution. [82] — Dose (for a HORSE ), 2 to 5 or 6 gr., twice or thrice daily; in farcy or glanders, 10 to 12 gr. In solution it is often employed as a wash or dipping to destroy vermin in cattle and sheep; but its use is not free from danger, particularly to the shepherds or dippers. [82] “As a therapeutic agent for horses, arsenious acid can be well dispensed with. It is, however, employed by some as a tonic, in doses of from 10 to 20 gr. daily; and by others as a vermifuge. When injudiciously administered death has been the result. By those of the old school it is extolled as a caustic, and a very powerful one doubtle ly it is; but there is this disadvantage attending its use—we cannot control its action, and, oftentimes, a most extensive and painful wound is caused by it. Occasionally it is resorted to for the eradication of warts; although a better plan is to extirpate them at once with the knife. When, however, this is inadmi ible, 1 part of arsenious acid, in very fine powder, may be mixed with 4 parts of lard, and a (small) portion of the compound applied, with friction, over and around the excrescence every other day, for three or four times. This will excite such a powerful sloughing action, that in about 10 days the warts will be thrown off.” (Prof. Morton.) Gen. commentary. The nece ary length of the preceding article, owing to the great importance of the subject in its relations to toxicology and medical jurisprudence, has left us little space for further remark here. In addition to what has been said on arsenical testing, it may be useful to caution the reader of the absolute nece ity of only employing tests and reagents which are themselves absolutely pure; and in which the operator has, by personal examination, failed to detect the slightest trace of arsenic. Commercial sulphuric, nitric, and hydrochloric acids, potash, soda, nitre, iron, and zinc, frequently contain arsenic; from which, however, they may be freed by chemical proce es; or they may be purchased in the pure state from respectable dealers in chemicals. But no a urance of the vender should be regarded as a proof of their purity. In all judicial investigations the absence of arsenic in the several tests and reagents, and the apparatus employed, must be demonstrated and sworn to. We may further add, that the results afforded by no single test can be depended on. In matters of such vast importance, the most ample confirmatory evidence must be sought. Marsh’s, Reinsch’s, La aigne’s, the sulphur, and the Reduction Tests, and their modifications, are those now generally preferred by toxicological chemists; each of which, with its confirmatory tests, are amply sufficient for the indisputable identification of arsenic. Modern toxicologists have abandoned most of the old proce es for the detection of arsenic, and have adopted one of two, which have been found more expeditious as well as more certain. These are the tests of Marsh and Reinsch, preferably the latter. Her a path’s Method is to obtain deposits by Reinsch’s Test on 4 or 5 pieces of No. 13 copper wire; each piece being about 2 1 ⁄ 2 inches long, and previously flattened and planished with a polished hammer for about one half its length. The deposit, with some of the adhering copper, scraped from one of these coated pieces, is sealed up hermetically in a tube for future production. The scrapings from three pieces of wire are separately submitted to the sublimation test in tubes bent in the form of an obtuse V capillary at one end, and about 3 ⁄ 10 ths of an inch in diameter at the other; the capillary leg being about three times as long as the larger one. The scrapings are placed in the bent part of the tube; and the flame of a small spirit lamp is so applied as to slowly drive the sublimate into the narrower portion of the tube, which is held rather higher than the other. If the deposit so obtained be mercury, it condenses in white shining globules;—if lead or bismuth, it does not rise but melts into a yellowish gla , which adheres to the copper; if tellurium, it falls as a white amorphous powder; if antimony, it does not rise at that low temperature; but if it be arsenic, it sublimes as arsenious anhydride, which condenses as minute octahedral crystals, looking, with the microscope, like very transparent grains of sand. One of these tubes containing the sublimed arsenious anhydride is then sealed up, like the first one, for future production. The capillary part of another tube containing the sublimate is then cut off, and carefully boiled in a few drops (10 to 15) of distilled water; and, when cold, 3 or 4 drops of the resulting solution is poured on a plate of white porcelain, and to this, by means of a gla rod, one drop of solution of ammoniacal sulphate of copper is added. The mixture is then carefully conducted on to a piece of white filtering-paper set on the surface of a smooth, clean, and dry chalk-stone, by which the moisture is absorbed, and the smallest portion ammonio-nitrate of silver test is then applied, in a similar manner, to 3 or 4 drops of the remaining solution; after which the pieces of paper with the spots are dried, and sealed up in separate tubes, as before, observing to exclude the light from that containing the yellow precipitate of arsenite of silver. A stream of sulphuretted hydrogen is then pa ed through the remaining tube containing the arsenical sublimate, by which the latter is converted into the yellow tersulphide—this too is sealed up. Here are now five tests—the metal, the acid, arsenite of copper, arsenite of silver, and yellow tersulphide of arsenic. It is now well known that certain soils contain arsenic, either as arsenite of lime or sulphide of arsenic; and which, under favorable circumstances, may permeate or be absorbed by a body, after interment. In judicial investigations following disinterment it is, therefore, nece ary to examine portions of the cemetery-earth taken from the grave, as well as from parts more or le distant from it. For this purpose the earth should be thoroughly dried in a water-bath, drenched with pure and concentrated hydrochloric acid, and allowed to stand for twenty-four hours. The mixture is then distilled, and the distillate tested for arsenic by Reinsch’s or Marsh’s test. Should the product of one distillation yield no evidence of arsenic, it should be returned to the retort, if nece ary, a second or even a third time, and the distillation repeated. The practice of employing an alkaline solution of white arsenic as an anti-smut steep for wheat, has lately arrested the attention of chemists. M. Audouard states that he has detected traces of arsenic in the crops raised from seed-wheat thus treated. But that which appears to be likely to prove much more dangerous is the introduction of arsenic into crops by the employment of crude superphosphate of lime as manure—a substance often rich in this poison. Dr Edmund Davy positively states that arsenic, as it exists in artificial manures, is taken up by plants growing where those manures have been applied! He found cabbages and turnips taken from fields manured with superphosphate give unmistakeable evidence of being ‘arseniated.’ These facts have some important bearings; for though the quantity of arsenic which occurs in such manures is not large when compared with their other constituents, and the proportion of that substance which is thus added to the soil must be nece arily small, still plants during their growth, as in the case of the alkaline and earthy salts, take up a considerable quantity of this substance. Further, as arsenic is well known to accumulate in soils, though not an accumulative poison in the animal system, the effects after some time will probably be, that vegetables raised on those continuously so manured will ultimately be found to contain such a proportion of arsenic as will exercise an injurious effect on the health of man and animals. The statement of M. Audouard has been disputed by M. Girardin, because he failed to detect arsenic in corn under the circumstances; and it is also denied by Dr A. S. Taylor, and others; but our own experiments, very carefully performed, confirm the a ertions of both Audouard and Davy. The ultimate consequences of pouring into the Thames such enormous quantities of disinfectants contaminated with arsenic, as has been done during the last three or four years, is another matter deserving consideration, and one which has been ably pointed out by Dr Letheby, in his reports as Officer of Health to the City of London. Dr Lois has found arsenic, often in large quantities, in ordinary bra , and bra utensils; and we have ourselves repeatedly found arsenic in the Britannia-metal, German-silver, and other cheap white alloys at present in such general use. The preceding facts are recommended to the careful attention of medical jurists. By an Act of Parliament [83] it is provided—1. That every vender of arsenic shall, before the delivery of the same to the customer, enter in a book or books kept for the purpose, the date of sale, name, and residence of the purchaser, in full, his or her condition or occupation, the quantity so sold, and the purpose or purposes for which it is required, in a form set forth in the schedule to the Act; which form or schedule shall be signed by the vender, and by the said purchaser, unle he be unable to write, when such fact shall be recorded in the said schedule by the vender; and this schedule, when a witne is required to the sale, shall also bear his signature, together with his place of abode:—2. Arsenic is not to be sold to a stranger, unle in the presence of a witne acquainted with both vender and purchaser:—3. No person to sell arsenic unle it be previously mixed with at least 1 oz. of soot or 1 ⁄ 2 oz. of indigo to the pound; unle such admixture would be injurious to the object for which it is intended, when not le than 10 lbs. is to be sold at any one time:—4. Penalty for evading the Act, either as vender, purchaser, or witne , £20:—5. Act not to extend to arsenic used in compounding prescriptions nor to the wholesale trade:—6. The word ‘arsenic’ to include ‘arsenious anhydride,’ and the arsenites, arsenic acid and the arseniates, and all other colourle poisonous preparations of arsenic. See Arsenic , Arsenic Acid , Lotions , Pills , Sheep-dipping , Soaps , Solutions , Wheat-steeps , Iron , Pota a , Soda , and other Bases, . . (also below ). [83] 16{?} Vict., c. xiii, 1851.