« PreviousContinue »
the attention of the analyst ought first to be directed towards finding small fragments of it in the stomach, and especially in those parts which are reddened by inflammation, in the food, the contents, etc. The food, the contents, the vomited matters, etc., are placed in a spacious glass jar, or beaker glass, distilled water poured on it, and the whole well stirred for some time; by this process the grains of arsenious acid are cleaned, and settle to the bottom of the vessel on account of their considerable density. The grains are easily recognized, and carefully picked out with a forceps, after having poured off the supernatant liquid.
To prove that the white grains, thus obtained, really are arsenious acid, the following experiments are made:
and very narrow part of a glass tube, of the shape shown in Fig. 1; immediately above, and also in the narrow part of the tube, is placed a thin splinter of freshly ignited charcoal. This part of the tube is now held horizontally in the very small flame of a common spirit lamp, in such a manner that the spot where the arsenious acid is placed may remain beyond the flame. When the charcoal is heated to redness, the open end of the tube is raised higher and higher, so that the tube becomes more and more inclined, until the spot where the arsenious acid is placed is also touched by the flame. If the particle was arsenious acid, it vaporizes; the vapor on its passage over the red hot charcoal is decomposed, and metallic arsenic is deposited beyond the charcoal, in the form of a black, or brownish-black, lustrous ring (arsenic mirror), as is illustrated by Fig. 2.
solved 3.15 per cent. of the opaque modification, and, on cooling and resting for 3 days, retained 1.7 ; that, with violent ebullition for an hour, it took up 4.63, and retained 2.47 on cooling and resting for 3 days; and that a saturated boiling solution of the transparent modifications contained 4.6 or 4.75 per cent., and on cooling and resting for 2 days retained 1.87 or 1.34.
The presence of organic principles appears to impair its solubility Christison found that a cup of tea, left beside the fire at a temperature of 2000 F. for half an hour upon 2 grains of the acid, does not entirely take up even that small quantity. These observations account for the fact, that frequently little or no arsenic is found in the fluid contents of the stomach, after an exbibition of the poison in the solid state.]
By applying heat, this incrustation of metallic arsenic vaporizes, becomes oxidized, and condenses in the wider part of the tube to a sublimate of arsenious acid, consisting of minute, lustrous crystals which, when seen with a lens or a microscope, appear as distinct octahedrons. The tube presents the appearance as shown in Fig. 3..
If the narrow part of the tube below the arsenic mirror is cut off, and the spot where the incrustation
is situated heated, by holding this end of the tube, slightly inclined upwards, into a small alcohol flame, a bluish white coloration of the flame will be observed where the arsenic vapor enters the flame, and the characteristic alliaceous odor is distinctly perceived on quickly approaching the tube to the nose.
The successful process of reduction, the odor of the vaporized arsenic mirror, and its conversion into a white crystalline sublimate, are sufficient proofs that the white substance under trial consists of arsenious acid.
$ 5. If several grains of arsenious acid have been collected, another experiment of reduction should be made, and the tube with the mirror handed over, together with the written report, to the proper authorities, as a corpus delicti ; the remaining grains are used for other experiments :
A particle is introduced into a glass tube sealed at one end, some dry acetate of soda, or potassa, added, and heat applied, when the indescribably offensive and characteristic odor of alkarsin (oxide of kakodyl) should be evolved. .
One or more fragments are finely powdered in a small agate mortar, the powder dissolved in boiling water, and the solution mixed with a few drops of a solution of nitrate of silver ; some very dilute caustic ammonia is then added, drop by drop, or by means of a glass rod, when the characteristic yellow precipitate of arsenite of silver will be produced.
The watery solution is acidulated with a few drops of hydrochloric acid, and some freshly prepared and strong sulphureted hydrogen water added, when a yellow precipitate of sulphuret of arsenic should be produced.
A fragment is heated in a test-tube with some nitric acid, to form arsenic acid; a few drops of nitrate of silver, and, afterwards, dilute ammonia, drop by drop, are added, when the reddish brown precipitate of arsenate of silver should be produced.
A fragment is converted into arsenic acid, as before, and the solution over-saturated with ammonia; a solution of chloride of ammonium, and, afterwards, a solution of sulphate of magnesia is added, when a crystalline precipitate of arsenate of magnesia-ammonia is thrown down, if the substance under examination was arsenious acid.
A fragment is used to form arseneted hydrogen, after the manner explained below.
$ 6. In examining the matter under examination for the presence of solid arsenious acid, proper regard should at the same time be paid to the presence of metallic arsenic, since the latter, known also under the name of “fly powder,” is as easily accessible to the public as white arsenic; it also possesses poisonous properties, and may, and indeed has been, employed for the purpose of poisoning; it always contains some arsenious acid.'
The fly powder is found in the shape of small black, or brownish black, lustrous, heavy scales or grains, the nature of which is as readily ascertained as that of arsenious acid. Heated in a glass tube (Fig. 1) alone, it yields an arsenic mirror. Thrown on incandescent charcoal, it evolves the characteristic alliaceous odor.—The powder, when heated with nitric acid, yields, with evolution of nitrous acid
vapor, a solution of arsenic acid (or of arsenions acid if the heat was not kept up for a sufficiently long time, or not sufficient nitric acid added); the liquid is carefully neutralized with ammonia, and then a few drops of nitrate of silver added, a reddish brown (eventually a yellow) precipitate is produced; after oversaturation with ammonia, a solution of sulphate of magnesia, containing chloride of ammonium, produces a white crystalline precipitate of arsenate of magnesia-ammonia; and an addition of sulphureted hydrogen water produces, immediately or after some time, and especially on gently heating, a yellow precipitate of sulphuret of arsenic.
[S 7. If a sulphide of arsenic has been administered, the examination of the contents of the stomach and intestines may yield some fragments of this substance. The bisulphide of arsenic, or realgar, is of a bright red, or orange yellow color, resinous lustre, and very brittle. The tersulphide, or orpiment, is a golden yellow crystalline substance. Both are volatile; heated in a glass tube closed at one end, they afford sublimates of different color; sometimes three sublimates are produced, the most volatile one being of a yellow, the next of a red, and the least volatile of a black color. They are insoluble in water, only slightly affected by acids, but soluble in ammonia ; on adding an acid to the ammoniacal solution, the sulphide is re-precipitated. Their nature is most satisfactorily and indubitably ascertained by subjecting a fragment to the treatment described in $ 13, and testing the resulting liquid after Marsh's method.
Fragments of Scheele's green (arsenite of copper), or other arsenites which may have been found in the