242 M edico- Legal Application of RiencKs Test for Arsenic. 



In this part of the subject, the most important practical consid- 

 erations are the determination of the amount of metallic copper to 

 be used, and the method of procedure in dense fluids, such as 

 broths, matter vomited, the blood, &c. In ascertaining the first, 

 two things are to be remembered ; 1st, that in the second step of 

 the operation, the sublimation, the tube should be as fine as pos- 

 sible ; and 2nd, the thickness of the deposit of arsenic is not at 

 all important, excepting that less copper is required, but there is 

 danger of its falling off in scales if too little is used. The only 

 rule that is applicable to all cases, is to examine a known small 

 proportion of the fluid first, and ascertain how much copper is 

 necessary to deprive it of all its poison ; the estimate thus made 

 may be applied to the remaining portions of the solution. If 

 sheet copper be used, it should be cut into strips, not exceeding 

 one fourth of an inch wide and one inch long, so that they may 

 be readily admitted into the subliming tube. The whole amount 

 of poison present may be sublimed in several tubes. To be cer- 

 tain that all the arsenic has been separated from the fluid, succes- 

 sive strips should be introduced, and the boiling continued longer 

 and longer, until no stain is produced in thirty minutes. 



The color and consistency of the fluids examined, may be sour- 

 ces of much embarrassment, when the usual tests are employed ; 

 and filtration is a necessary part of the process when the fluid re- 

 agents are used. But neither of these qualities opposes serious 

 impediments to the method under consideration. The coagula- 

 bility of the solution is however a serious obstacle, because the 

 arsenic is shut up in the coagula, and cannot be brought into 

 contact with the copper. To remedy this evil, the eoagulum 

 should be cut up into minute pieces and warmed along with mu- 

 riatic acid, the consequence of which is that all the poison will 

 be dissolved by the acid, which is one of the best solvents of 

 arsenic. The solid parts should be afterwards separated, by strain- 

 ing through a strong piece of cloth of close fabric. In this way, 

 the drug can be collected out of blood. When the coats of the 

 stomach are to be tested, they should be cut up, as is usually pre- 

 scribed, and boiled with dilute acid. In operating upon fluids 

 which are not yet coagulated, it is best to add dilute hydrochlo- 

 ric acid before heating, for in this way they do not form so dense 

 a solid, but the acid exerts its solvent action throughout the mass, 

 and may be afterwards pressed out by straining. 



