218 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



quantitative accuracy of the methods for the separation of 

 arsenic from the tissues which are ordinarily made use of, 

 and to devise an improved method of his own. The improve- 

 ment has reference in the first place to the separation of the 

 arsenic from the organic matter, and in the second to obtain- 

 ing it in a weighable form. For the former, 100 grammes of 

 the finely divided animal matter is placed in a porcelain cap- 

 sule with 30 grammes of pure nitric acid, and moderately 

 heated. The mass at first liquefies, and then thickens and 

 becomes orange-colored. The capsule is taken from the fire 

 and 5 grammes of pure sulphuric acid are added. Heat is ap- 

 plied till white fumes appear, 10 or 12 grammes of nitric acid 

 are allowed to flow drop by drop on the residue, and the whole 

 is heated to carbonization. An easily pulverizable mass is 

 thus obtained, which is exhausted with boiling water, filtered, 

 the filtrate reduced with a few drops of hydro-sodium sulphite, 

 and precipitated as usual with hydrogen sulphide. The im- 

 provement in the determination consists in passing the gas 

 evolved from a Marsh apparatus through a tared glass tube 

 heated to redness by charcoal for a length of 20 to 25 cen- 

 timeters. After the arsenic is all carried over, the tube is de- 

 tached and a2:ain weig-hed. The difiference is the amount of 

 arsenic, the results being accurate. Five milligrammes of 

 arsenous oxide mixed with 100 grammes of muscular tissue 

 gave when treated by this process rings weighing respectively 

 3.72 and 3.67 milligrammes; the theoretical quantity being 

 3.79. Bull. Soc. CA., II., xxiv., Oc^oJer, 1875, 250. 



