DETECTION OF ARSENIC.] 



CHEMISTRY. 



383 



he may grope long enough, and not only not succeed, but 

 waste the preserved matter, and so prevent discovery or 

 accurate analysis impossible. Two instances of this 

 nature came under our notice some few years ago. . In 

 one case, it was suspected that wine, which had been 

 partaken of by several persons, had accidentally been 

 kept in a bottle which had contained poison. The 

 anah-st was a clever chemist, but no physiologist ; he 

 never asked respecting the symptoms which had exhibited 

 themselves. The quantity of poison, whatever it was, 

 was exceedingly minute; and, for want of a proper 

 clue, he examined for antimony, corrosive sublimate, 

 be. We happened to suggest, that as it was wine, it was 

 highly possible arsenic mi^ht have been communicated 

 to the bottle by its having been cleaned with shot. We 

 also learned that the usual symptoms of arsenical poison- 

 ing had been noticed, but in a mild form. On using 

 Marsh's test, a minute quantity of arsenic was actually 

 discovered. In this case, had the chemist possessed 

 medical knowledge, he might have gone straight to his 

 work. 



The second instance to which we shall refer, was that 

 of suspected poisoning by arsenic ; in which the medical 

 man was utterly deficient of all the capabilities of a 

 chemical analyst. In attempting the analysis, the entire 

 contents of the stomach, with itself, were put into an 

 evaporating dish ; heat was applied ; and, for want of 

 rare and experience, the dish was cracked, and 

 the whole of its contents lost. The fragments, however, 

 were collected ; and, in more experienced hands, afforded 

 the evidence sought for. 



We may, therefore, be permitted to nrge on coroners 

 and juries tiie necessity, in every caff in which suspicion 

 lurks, that all available material should be placed in 

 competent hands only, lest that which is of value may 

 oe lost, or crude and indigested opinions be expressed, to 

 the damage of the suspected one, or the defeat of the 

 ends of justice. 



The directions we are about to give, are simply in- 

 tended to enable the tyro in chemical science to apply 

 his knowledge in gaining an insight into the mmlns 

 operand*. If he be desirous of repeating the experi- 

 ments on animals, he will do best to choose rabbits for 

 his purpose, because he will not have to experience that 

 disgust which the analysis of the stomach of cats, dogs, 

 <i:c., is apt to excite. An anatomist soon gets overall 

 topi- amislines* in the matter, whilst a tyro has to over- 

 come many offensive details. 



The belly of the poisoned animal is to be carefully 

 opened by means of a sharp knife, or lancet ; and the 

 whole of the stomach, from the throat to the gut, re- 

 moved, unopened just as is done in trussing fowls. 

 We shall be excused by our professional friends if we 

 use unprofessional and plain language. The stomach, 

 iVc. , is then to be placed in a clean dish, and divided 

 lengthwise by means of the lancet, so as to expose the 

 whole interior. Tliis may be then carefully examined 

 by means of a Stanhope lens, to detect the presence of 

 any white powder. If such be present, remove all of it 

 carefully with a bone spoon, or spatula, and wash it off 

 carefully into a test-tube ; put this aside for a time. 



Supposing no powder to be seen which will depend 

 on the quantity of arsenic given, and the length of 

 time which has elapsed from its administration put the 

 whole of the contents of the dish into an evaporating 

 dish containing a little distilled water ; and turning the 

 stomach and gut inside out, wash them carefully for 

 some time. This will wash or dissolve out all the un- 

 observed powder, and that which has been dissolved or 

 suspended in the food. Add to the mixture some strong 

 acetic acid ; and then cautiously evaporate the whole to 

 dryness, taking care not to do so beyond what is abso- 

 lutely necessary to ensure that all vapour is driven off. 

 Allow the contents of the dish to cool, and then add 

 some perfectly pure hydrochloric acid : great care must 

 be taken in this respect ; because all commercial acid 

 contains arsenic, which would vitiate the result. Heat the 

 acid with the contents of the dish for some time, adding 

 more as evaporation proceeds ; and after the lapse of 



half-an-hour, pour the liquid into a clean glass. By 

 these means all the arsenious acid will have been con- 

 verted into the chloride, and the solution will be free 

 from organic matter. The rest of the process is very ; 

 simple. Part of the solution may be boiled with some 

 pure copper, according to Reinsch's plan, and the rest 

 introduced into the hydrogen bottle, according to the 

 method of Marsh. By means of either process, both of 

 which we have already described, any arsenic present 

 will be at once detected. 



The powder previously removed into the test-tube 

 may be heated with hydrochloric acid, and the 

 same tests applied as above, when the results afforded 

 will, of course, be the same, although more distinct in 

 their indications. 



We have thus endeavoured to put the student into 

 possession of what we consider to be the best mode of 

 conducting an elementary analysis for the detection of 

 arsenic. We need only add, that in this, as in all other 

 chemical investigations, care and keen observation are 

 eminently required. In analysing vomited matter, the 

 practitioner must follow the same course ; if, however, 

 Marsh's test be adopted, care is required that the animal 

 matter do not cause so much frothing up as to cast the 

 contents out of the hydrogen bottle. This may partly 

 be prevented by pouring a few drops of almond oil on 

 the surface of the liquid in the bottle. It is an excellent 

 plan to heat the tube through which the gas issues 

 before reaching the jet. This is easily done by bending 

 the tube in the manner shown in the following engraving 

 Fig. 68. 



The flame may be received in a bent tube, as repre- 

 sented below, when the double layer of metallic arsenic, 

 and the white arsenic, will be readily noticed. 



Fig. 69. 



We have already frequently noticed the combination 

 of arsenic with copper, forming the pigment termed 

 Scheele's green. The chloride has also been often men- 

 tioned in our previous remarks. The chief other com- 

 pnunds of the metal are those with sulphur ; one of 

 which, realgar, is an ore of the metal, of a red colour, 

 containing one equivalent of arsenic to two of sulphur. 

 The other is known by the name of orpiment ; and it 

 has a yellow colour. 



Arsenic, like copper and iron, produces an acid bearing 

 its name ; its symbol is As O s . It forms salts witli 

 bases ; is a white substance ; and yields a red precipitate 

 with nitrate of silver alone ; whilst arsenious acid requires 

 the addition of ammonia. By this difference, with the 

 colour of the precipitate, the two may be distinguished. 

 Before concluding these remarks, we refor our readers 

 to what we have stated in reference to the combination 



