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PROCEEDINGS OF THE AMERICAN ACADEMY. 



SERIES D. 

 Distillation Method. 



To show the calculation of the analysis, one example will suffice : 



Comparison of Methods. In order to compare more fairly the distil- 

 lation method with the method of evaporation, the latter was slightly 

 modified to secure the most favorable conditions for the recovery of 

 the arsenic. 200 c.c. urine were evaporated to about 50 c.c, and then 

 treated with 25 c.c. conceiitrated nitric acid and 5 c.c. sulphuric acid. 

 Evaporation was continued until the fumes of sulphuric acid appeared, 

 which left a dark residue containing a large amount of organic matter. 

 By successive addition of small amounts of nitric acid and heating, 



