CHEMICAL TOXICOLOGY 



Introductory. — Under the respective headings in the text 

 the chief tests for the poisons dealt with have been given. 

 At first sight it may appear that few reactions have been 

 quoted. Thus in the case of arsenic many well-known pre- 

 cipitation tests have been omitted. This has been done 

 because it seemed advisable only to name those tests which 

 are suitable for the recognition of traces, which are as 

 characteristic as possible, and which can be applied to the 

 substance in the form in which it is obtained from the 

 material under research. 



In the present section some details are given as to the 

 general methods of separation of poisons from organic 

 matter in the laboratory. For analytical purposes the 

 poisons fall into four groups, viz. : 



A. Volatile poisons. 



B. Heavy metals and metalloids. 



C. Non-volatile organic poisons. ' 



D. Bases, acids, and alkali salts. 



Preliminary Observations. — Before starting a systematic 

 search for poisons, certain general observations ought to be 

 made. These include colour. The existence of coloration, 

 either local or diffused, is a valuable guide. A yellow colour 

 suggests nitric and picric acids; greenish-blue points to 

 copper ; green to chromium compounds ; black to iron com- 

 pounds of tannin ; blue may be due to indigo or Prussian 

 blue, used as colouring agents for vermin powders, but the 

 quantity is usually too small to be perceived ; specks of red 



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