The soda, and boil the fused mass with solution of soda. 2. BOILING WATER FAILS TO DISSOLVE THE SUBSTANCE, OR EFFECTS 284 ONLY PARTIAL SOLUTION; THE FLUID ADMITS OF FILTRATION. Filter, and treat the filtrate either as directed § 187, or, should it require decolorization, according to the directions of § 219, 1. The residue may be of various kinds. a. IT IS FATTY. Remove the fatty matters by means of ether, and should a residue be left, treat this as directed § 173. b. IT IS RESINOUS. Use alcohol instead of ether, or apply both liquids successively. c. It is of a DIFFERENT NATURE, e.g., woody fibre, &c. a. Dry, and ignite a portion of the dried residue in a porcelain or platinum vessel, until total or partial incineration is effected; boil the residue with nitric acid and water, and examine the solution as directed § 187, III. (109); if a residue has been left, treat this according to the directions of § 201. B. Examine another portion for the heavy metals, in the manner directed § 219, 1, a; since in a, besides the compounds of mercury which may be present, arsenic, cadmium, zinc, &c., may volatilize. 7. Test the remainder for ammonia, by triturating it together with hydrate of lime. 3. THE SUBSTANCE DOES NOT ADMIT OF FILTRATION OR ANY OTHER 285 MEANS OF SEPARATING THE DISSOLVED FROM THE UNDISSOLVED PART. Treat the substance in the same manner as the residue in 2. As regards the charred mass (2 a), it is often desirable to boil the mass, carbonized at a gentle heat, with water, filter, examine the filtrate, wash the residue, incinerate it, and examine the ash. 2. Detection of Inorganic Poisons in Articles of Food, in Dead $220. The chemist is sometimes called upon to examine an article of 286 food, the contents of the stomach of an individual, a dead body, &c., with a view to detect the presence of some poison, and thus to establish the fact of a wilful or accidental poisoning; but it is more frequently the case that the question put to him is of a less general nature, and that he is called upon to determine whether a certain substance placed before him contains a metallic poison; or, more pointedly still, whether it contains arsenic, or hydrocyanic acid, or some other particular poison-as it may be that the symptoms * Compare: a. Fresenius, "die Stellung des Chemikers bei gerichtlich chemischen Untersuchungen," &c. (Annal. der Chemie und Pharm. 49, 275); and b. Fresenius and v. Babo's "Abhandlung über ein neues, unter allen Umständen sicheres Verfahren zur Ausmittelung und quantitativen Bestimmung des Arsens bei Vergiftungsfällen.”—Annal. der Chemie und Pharmacie, 49, 287. point clearly in the direction of that poison, or that the examining magistrate has, or believes he has, some other reason to put this question. It is obvious that the task of the chemist will be the easier, the more special and pointed the question which is put to him. However, the analyst will always act most wisely, even in cases where he is simply requested to state whether a certain poison, e. g. arsenic, is present or not, if he adopts a course of proceeding which will not only permit the detection of the one poison specially named, the presence of which may perhaps be suspected on insufficient grounds, but will moreover inform him as to the presence or absence of other similar poisons. But we must not go too far in this direction either; if we were to attempt to devise a method that should embrace all poisons, we might unquestionably succeed in elaborating such a method at the writing-desk; but practical experience would but too speedily convince us that the intricate complexity inseparable from such a course, must necessarily impede the easy execution of the process, and impair the certainty of the results, to such an extent indeed, that the drawbacks would be greater than the advantages derivable from it. Moreover, the attendant circumstances permit usually at least a tolerably safe inference as to the group to which the poison belongs. Acting on these views, I give here,— 1. A method which ensures the detection of the minutest traces of arsenic, allows of its quantitative determination, and permits at the same time the detection of all other metallic poisons. 2. A method to effect the detection of hydrocyanic acid, which leaves the substance still fit to be examined both for metallic poisons and for vegeto-alkalies. 3. A method to effect the detection of phosphorus, which does not interfere with the examination for other poisons. This Section does not, therefore, profess to supply a complete guide in every possible case or contingency of chemico-legal investigations. But the instructions given in it are the tried and proved results of my own practice and experience. Moreover, they will be found sufficient in most cases, the more so as I shall append to the Section on the vegeto-alkalies the description of a process by which the detection of these latter poisons in criminal cases may be effected. I. METHOD FOR THE DETECTION OF ARSENIC (WITH DUE REGARD TO THE POSSIBLE PRESENCE OF OTHER METALLIC POISONS. § 221. Of all metallic poisons arsenic is the most dangerous, and at the 287 same time the one most frequently used, more particularly for the wilful poisoning of others. And again, among the compounds of arsenic, arsenious acid (white arsenic) occupies the first place, because (1) It kills even in small doses; (2) It does not betray itself, or at least very slightly, by the taste; and (3) It is but too readily procurable. As arsenious acid dissolves in water only sparingly and-on account of the difficulty with which moisture adheres to it-very slowly, the greater portion of the quantity swallowed exists usually in the body still in the undissolved state; as, moreover, the smallest grains of it may be readily detected by means of an exceedingly simple experiment; and lastly, as-no matter what opinion may be entertained about the normal presence of arsenic in the bones, &c.— this much is certain, that at all events arsenious acid in grains or powder is never normally present in the body, the particular care and efforts of the analyst ought always to be directed to the detection of the arsenious acid in substance-and this end may indeed usually be attained. A. Method for the Detection of undissolved Arsenious Acid. $ 222. 1. If you have to examine some article of food, substances re- 288 jected from the stomach, or some other matter of the kind, mix the whole as uniformly as may be practicable, reserve one-third for unforeseen contingencies, and mix the other two-thirds in a porcelain dish with distilled water, with a stirring rod; let the mixture stand a little, and then pour off the fluid, together with the lighter suspended particles, into another porcelain dish. Repeat this latter operation several times, if possible, with the same fluid, pouring it from the second dish back into the first, &c. Finally, wash once more with pure water, remove the fluid, as far as practicable, and try whether you can find in the dish small, white, hard grains which feel gritty and grate under the glass rod. If not, proceed as directed § 223. But if so, put the grains, or part of them, on blotting-paper, removing them from the dish with the aid of pincers, and try the deportment of one or several grains upon heating in a glass tube, and of some other grains upon ignition with a splinter of charcoal (compare § 131, 11). If you obtain in the former experiment a white crystalline sublimate, in the latter a lustrous arsenical mirror, the fact is clearly demonstrated that the grains selected and examined consisted really of arsenious acid. If you wish to determine the quantity of the poison, unite the contents of both dishes, and proceed as directed § 223. 2. If a stomach is submitted to you for analysis, empty the contents into a porcelain dish, turn the stomach inside out, and (a), search the inside coat for small, white, hard, sandy grains. The spots occupied by such grains are often reddened; they are also frequently found firmly imbedded in the membrane. (b) Mix the contents in the dish uniformly, put aside one-third for unforeseen contingencies, and treat the other two-thirds as in 1. The same course is pursued also with the intestines. In other parts of the body with the exception perhaps of the pharynx and œsophagus-arsenious acid cannot be found in grains, if the poison has been introduced through the mouth. If you have found grains of the kind described, examine them as directed in 1; if not, proceed according to the instructions of § 223. B. Method for the Detection of Arsenic in whatever Form of Combination it may exist, which allows also a Quantitative Determination of that Poison, and permits at the same time the Detection of other Metallic Poisons which may be present.* $223. If you have found no arsenious acid by the method described in 289 A, evaporate the mass in the porcelain dish, which has been diluted by washing with water (see A, 1), on the water-bath, to a pasty consistence. If you have to analyze a stomach, intestinal tube, &c., cut this into pieces, and add two-thirds to the mass in the dish. In examining other parts of the body (the lungs, liver, &c.), cut them also into pieces, and use two-thirds for the analysis. The process is divided into the following parts.t 1. Decolorization and Solution. Add to the matters in the porcelain dish an amount of pure 290 hydrochloric acid about equal to, or somewhat exceeding the weight of the dry substances present, and sufficient water to give to the entire mass the consistence of a thin paste. Heat the dish now on the water-bath, adding every five minutes about two grammes (half a drachm) of chlorate of potassa to the hot fluid, with stirring, and continue the same operation until the contents of the dish show a light-yellow color and a perfectly homogeneous appearance, and are quite fluid. When this point is attained, add again a portion of chlorate of potassa, and then remove the dish from the water-bath. When the contents are quite cold, transfer them cautiously to a linen strainer or to a white filter, according to the greater or less quantity of substance; allow the whole of the fluid to pass through, and put the filtrate aside. Wash the residue well with hot water, and dry it; then mark it I., and reserve for further examination, according to the instructions of § 223, 8 (303). Evaporate the washings on the water-bath to about 3 or 4 oz. (about 100 grm.), add this, together with any precipitate that may have formed therein, to the principal filtrate, and then add to the united fluid, which is still very acid, some solution of sulphite of soda, with stirring, until the odor of sulphurous acid becomes distinctly perceptible. Then heat the mixture again gently on the water-bath until the excess of the sulphurous acid is expelled, which will take about an hour. 2. Treatment of the Solution with Hydrosulphuric Acid (Separation of the Arsenic as Tersulphide, and, respectively, of all the Metals of Groups V. and VI. in form of Sulphides). When the fluid obtained in 1, and which amounts to about twice 291 This method is essentially the same as that which I have elaborated and published in 1844, jointly with L. v. Babo; compare "Annal. der Chemie und Pharmacie," Bd. 49, p. 308. I have since that time had frequent occasion to apply it; I have also had it tried by others, under my own inspection, and I have invariably found it to answer the purpose perfectly. I think I need hardly observe that in such extremely delicate experiments the vessels and reagents used in the process must be perfectly free from arsenic, from heavy metals in general, and indeed from every impurity. : or three times the quantity of hydrochloric acid used, is quite cold, pour it into a beaker, transmit through it, for about 12 hours, a slow stream of washed hydrosulphuric acid gas, rinse the delivery pipe with some ammonia, add the ammoniated solution thus obtained to the principal fluid, cover the beaker lightly with unsized paper, and put it in a moderately warm place (about 86° F.), until the odor of hydrosulphuric acid has nearly disappeared. Collect the precipitate obtained in this manner on a moderately sized filter, and wash, until the washings are quite free from chlorine. Concentrate the filtrate and washings somewhat, mix the fluid in a flask with ammonia to alkaline reaction, then with sulphide of ammonium, closely cork the flask, which must now be nearly full, and reserve for further examination according to the instructions of § 223, 9 (307). 3. Purification of the Precipitate produced by Hydrosulphuric Acid. Thoroughly dry the precipitate obtained in 2-which, besides 292 organic matters, must contain, in form of tersulphide, the whole of the arsenic present in the analyzed substance, as well as, in form of sulphides, all the metals of Groups V. and VI. which may happen to be present-together with the filter, in a small porcelain dish, heated on the water-bath; add pure fuming nitric acid (perfectly free from chlorine), drop by drop, until the mass is completely moistened, and then evaporate on the water-bath to dryness. Moisten the residue uniformly all over with pure hydrated sulphuric acid, previously warmed; then heat for two or three hours on the water-bath, and finally on the air- sand- or oil-bath at a somewhat higher, though still moderate temperature (338° F.), until the charred mass becomes friable, and a small sample of it-to be returned afterwards to the mass-when mixed with water and then allowed to subside, gives a colorless fluid; should the fluid standing over the sediment show a brownish tint, or the residue, instead of being friable, consist of a brown, oily liquid, add to the mass some cuttings of pure Swedish filtering paper, and continue the application of heat. By attending to these rules you will always completely attain the object in view, viz., the destruction of the organic substances, without loss of any of the metals. Warm the residue on the water-bath, with a mixture of 8 parts of water and 1 part of hydrochloric acid, filter, wash the undissolved part thoroughly with hot, distilled water, with addition of a little hydrochloric acid, and add the washings, which must be concentrated if necessary, to the filtrate. Dry the washed carbonaceous residue, then mark it II., and reserve for further examination according to the instructions given in § 223, 8, b (304). 4. PRELIMINARY EXAMINATION FOR ARSENIC AND OTHER METALLIC POISONS OF GROUPS V. AND VI. (Second Precipitation with Hydrosulphuric Acid). The clear fluid obtained in 3 contains all the arsenic which 293 may have been present, in form of arsenious acid, and may con |