284 VBTEEINAEY TOXICOLOGY 



Two operations are performed : 



(1) A Reinsch test direct on the material. 



(2) Partial destruction of the organic matter with 



nitric acid alone, or along with sulphuric acid. 

 This is the original method of Orfila, and is 

 recommended by the German authorities in 

 dealing with such materials as solid foodstuffs. 



1. The material in suitable quantity, from J ounce to 

 6 or 8 ounces, according to circumstances, is boiled in a 

 clean flask, with hydrochloric acid of about 16 per cent, 

 strength, and pure copper foil, or gauze. Foil is better 

 than gauze because the coating of a trace is more easily 

 seen, on account of the smaller surface as compared with 

 gauze. The flask is provided with an upright tube con- 

 denser, so that boiling may be prolonged without loss of 

 water, or of arsenic by volatilisation as arsenious chloride. 

 Before use the whole apparatus ought to be ' blanked ' by 

 boiling pure acid and copper together for half an hour, and 

 showing that no deposit takes place on the metal. It is 

 most important to remember that hydrochloric is the only 

 suitable acid. In the event of free chlorine, potassium 

 chlorate, nitric acid, or nitrates being present, solution of 

 the copper will occur. In such case the acid mixture must 

 be gently warmed until free of chlorine before putting in 

 the copper. 



In this test the following metals are deposited upon the 

 copper : Arsenic, antimony (bismuth), silver, and mercury. 

 If much of any of these is present, a deposit is seen on the 

 copper in a few moments after heating, and unless the strip 

 is taken out the whole of the copper will speedily pass into 

 solution, and the deposit beaome disseminated throughout 

 the mass and lost. Fresh strips are to be added and re- 

 moved when well coated, until eventually no further deposi- 

 tion occurs. 



If mere traces are present, boiling at a gentle heat ought 

 to be continued for at least an hour before abandoning the 

 test. 



