CHEMICAL TOXICOLOGY 283 



It is unnecessary to make separate tests for each of these 

 metals, although, having detected one or more of them, it 

 may be needful to make special extractions of the original 

 material for the purposes of estimation, and the obtaining of 

 a specimen as a corpus delicti. 



General schemes may be devised to cover a preliminary 

 and comprehensive search, and several such schemes are 

 available, each of which has its special claims to excellence, 

 and its special advocates. The vital point is the destruction 

 of organic matter, which is an extremely tedious process to 

 carry out to completion. The English analysts rather 

 appear to favour the complete destruction of organic matter 

 either by ashing with previous addition of nitric and sulphuric 

 acid, in which process all the organic matter is burnt away, 

 or its destruction by prolonged heating with concentrated 

 sulphuric acid in the presence of potassium sulphate. In 

 the former process mercury is entirely lost, and in both 

 there is danger of losing arsenic. Both are tedious, and, as 

 our repeated experience has shown, do not possess advantage 

 in point of accuracy.* The German experts rely on the 

 process of Presenius and Babo, which consists in the partial 

 oxidation of albumins by warming with hydrochloric 

 acid, and repeated small quantities of potassium chlorate 

 (or chloric acid). The nascent chlorine is an effective 

 oxidising agent, and the process yields a clear yellow solu- 

 tion, from which excess of chlorine must be driven by a 

 current of air. Erom this acid liquid sulphuretted 

 hydrogen, after prolonged standing, gives sulphides of 

 arsenic, antimony (tin, cadmium, bismuth), mercury, 

 silver, lead, and copper, along with sulphur, and organic 

 matter. In practice this method is more tedious and 

 no more accurate than the comparatively simple scheme 

 outlined below, which has been adopted as the result 

 of very extended practice and comparisons with other 

 processes, but which merely systematises well-known 

 analytical processes. 



* See Lander and Winter, Analyst, 1908. 



