CllKMiSTKY 



[DKTECTIOX or AI 



with UM modes which my be ad..|.t. .1 t.> detect 

 the preMno* of anenio oommencing with come oom- 

 Irtively rough experinwnU, ai . then giving those 

 refined method! which the analytical chemist adopt* iu 

 oases which form the rabjeot of judicial investigation. 

 If the student proceed successively with each, he may 

 aoon acquire (kill in the detection of the poiion. 



(a.) Introduce a few grains of white anenio iuto a 

 tort-tube, and apply the heat of a ipirit-lamp to the 

 powder. It will volatilue and oondense on the cool part 

 . .f the tube aa a white crystalline substance. 



(6.) Mix a little white anenio with some powdered 

 charcoal, and apply heat a* before. The oxide will be 

 reduced, and mi la! lie arsenic will be produced in dark 

 metallic crystals. 



(c.) Apply heat to these crystals, when they will 

 immediately volatilue, recondensing in some cooler part 

 ,: ::.,. tab*. 



The foregoing experiment* will illustrate the cha- 

 racteristics of arsenic and anenioua acid, and the method 

 by means of which the metal may be reduced. 



Anenio has, like antimony, the power of combining 

 with hydrogen, and of forming what is termed arseu- 

 iuretted hydrogen. This fact has been taken advan- 

 tage of by Mr. Marsh, to afford a most ingenious and 

 effective means for discovering the presence of arsenic 

 in minute quantities. The best mode of illustrating 

 this is as follows : 



Into the bottle represented in the following figure, in- 

 troduce some water, zinc-shavings, and a little sulphuric 

 acid ; just as is done in malting hydrogen gas. Refit the 

 tit. 7. tube and cork ; and after having allowed 

 the mixture of air and hydrogen to escape, 

 so as to prevent any danger of explosion, 

 ignite the gas, and hold against the flame a 

 white porcelain plate. If the zinc and acid 

 be pure, nothing will be deposited on the 

 plate except a little water. Dissolve a 

 small portion of arsenious acid in hydro- 

 chloric acid, heating the mixture. Whan 

 the solution is effected, pour a few drops 

 into the bottle producing hydrogen, and 

 instantly replace the tube. After a few 

 seconds, apply a light to the jet ; when it will be noticed 

 that the flame has a blue colour ; and if a cold plate be 

 now held against it, crystals of arsenious acid will be at 

 once produced ; in the centre of which will be a black 

 mark. Instead of the plate, let the flame play inside 

 of a glass-tube. The arsenious acid and arsenic in a 

 metallic state will both be deposits!. These may then 

 be again volatilised in the manner already referred to in 

 experiments a and c, above. We need scarcely state, that 

 in accurate analysis, it is of the utmost importance that 

 all the materials employed should be pure. Zinc and 

 sulphuric acid frequently contain arsenic ; hence, if the 

 loiiiinercial articles be used, they may possibly afford 

 arsenic, which would render all results obtained value- 

 less. This precaution, the experienced chemist, of 

 course, always attends to ; and U at all times scrupulously 

 careful as to the purity of his testa. 



If a piece of clean copper be dipped into the hot 

 notation of arseuious acid just mentioned, and boiled 

 therein, the copper will become coated, arsenic being re- 

 duced on its surface. The <.] r flip may then be 

 removed ; and after being washed u. water and dried, the 

 arsenic may be sublimed from its surface, if it be intro- 

 duced into a test-tube, and heated by means of a spirit- 

 lamp. This plan is Reinsch's tost ; but unless quite pure 

 copper be employed, the result* are vitiated and value- 

 less ; for copper frequently contains a portion of arsenic, 

 obtained from it* ores. In a late case of suspected 

 poisoning, the accidental discovery of the impurity of 

 the copper, after the analysis had been effected, alone 

 saved the condemnation and execution of the suspected 

 individual 



Arsenic in solution may also be detected by liquid 

 testa. Tha* of nitrate of silver with ammonia, when 

 the alkali U not in excess, affords a yellow precipitate ; of 

 sulphate of copper and ammonia, a rich green one ; and 



a stream of sulphuretted hydrogen produces a \ 

 sulphide. These tests, however, are never relied on in 

 accurate investigations. 



The foregoing remarks and experiment* will give our 

 readers a general idea of the various methods employed 

 to detect arsenic. We shall now direct attention to the 

 usual moilu optrandi in post-mortem investigat 

 w -hen death has been suspected to have arisen from the 

 use or administration of arsenic as a poison. 



Arsenic is generally taken in comparatively small 

 quantities . e., of a tew grains only. It is not very 

 soluble in water of the temperature of the stomach ; but 

 it must be borne in mind that the acids in the stomach 

 greatly facilitate its solution. When taken in large 

 doses, it produce* vomiting, which relieves the stomach 

 of a portion of the poison. An instance of this kiixl 

 occurred in Glasgow some years ago, when not less than 

 a quarter of an ounce of the poison was discovered in 

 the stomach of the deceased person, who had been vio- 

 lently sick for some time before death. The symptoms 

 of arsenical poUouing are, violent retching, heat in the 

 throat and palate, a metallic taste in the mouth, and 

 great irritability of the whole system. The face wears 

 an anxious appearance ; and, indeed, most of the symp- 

 toms produced by irritant poisons are manifested. It is 

 of the utmost importance that medical aid should at 

 once be secured ; but in the absence of this, the only 

 antidote which can be readily obtained, is that of the 

 peroxide of iron. To obtain it, add carbonate of am- 

 monia to the ordinary tincture of steel, as long as a 

 powder is thrown down ; and to save time, pour off the 

 clear liquid, adding water to the powder ; again pour off 

 the liquid, and add sufficient water to allow of the pow- 

 der being readily suspended in it. Stir it up, and 

 administer a wine-glass full continually, taking care 

 that as much as possible of the oxide be swallowed at 

 each dose. Meanwhile medical aid may have been 

 obtained, and the patient no left in experienced hands. 

 When the remedy cannot be arrived at, every attempt 

 should be made to make the patient vomit, so as to 

 clear the stomach as much as possible of the poison. If 

 such precautions be taken before inflammation com- 

 mences, considerable chance exists of preventing a fatal 

 termination, because, as we before remarked, the com- 

 parative insolubility of arsenic favours the chance of 

 recovery. 



When any suspicion of foul play exists, every drop 

 thrown up from the stomach should be carefully pre- 

 served, and be left untouched until placed in competent 

 hands for analysis. Many a life has been preserved 

 through the over-cunning of criminals. A small dose of 

 arsenic is far more likely to prove fatal than a large one, 

 for reasons we have already assigned ; but the non-suc- 

 cess of one attempt by no means leads to the supposition 

 that it will not be repeated. Therefore, if symptoms 

 such as we have described have been noticed, and any 

 suspicion exist, then the analysis of the ejected matter 

 may, if it do not lead to detection, terrify by the dis- 

 covery it affords. 



In post-mortem examinations, much chemical skill is 

 required ; and wo cannot but remark on the careless and 

 loose manner with which such delicate operations are 

 entrusted to what we may safely call unpractised 

 and ignorant persons. The ordinary medical prac- 

 titioner is often one v hose education has been generally 

 on each branch of the knowledge of his profession ; and 

 those of us who are acquainted with the course of che- 

 mistry through which most students pass in our hospitals 

 and colleges, previously to passing their examination, 

 would not trust to such the analysis of a piece of chalk. 

 Chemical analysis requires, for its successful pursuit, a 

 most extensive knowledge, a careful manipulation, and 

 a delicately-balanced judgment which nothing but 

 years of practice can afford when detection, in case* 

 of poisoning, is required. Other qualifications are also 

 requisite ; for if a chemist be merely informed that .1. ,,ili 

 lias been caused by an irritant poison unless ho have 

 xullieifiit medical knowledge to cuaMe him to anticipate 

 iiis progruss by an acquaintance with the symptom 



