SANGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 337 



no arsenious when arsenic was ingested as the trioxide. Selmi 22 states 

 that he found in the urine of a dog poisoned by arsenic a volatile com- 

 pound of the element. The reference gives no analytical details and 

 the original is not accessible to us. It is not improbable, however, 

 from the analogy to phosphorus, that arsenic finds its way into the 

 urine as an arseniate. If this be the case, the question will perhaps 

 be asked if small amounts of arseniate, when distilled with hydrochlo- 

 ric acid, would be recovered in the distillate or would require a pre- 

 liminary reduction before distillation. 



Mayerhofer 23 has shown that if arsenic acid is distilled with a suf- 

 ficiently large quantity of hydrochloric acid, it is converted to arsenic 

 trichloride, chlorine being given off, since the pentachloride does not 

 exist under ordinary conditions. In our method the concentration of 

 the hydrochloric acid in 100 cc. of its solution would be so great 

 compared with that of the arseniate that a complete conversion to tri- 

 chloride might be predicted. That this is the case is shown by the 

 following analyses, in which the arsenic acid used was prepared by 

 evaporating a measured quantity of arsenious acid solution to dryness 

 with nitric acid before adding to the urine. 



SERIES C. 



Distillation Method in Presence of Arseniates. 



A nalyses of Urine. The method was finally tested by the analysis 

 of six samples of urine to which varying amounts of arsenic had been 

 added by one of us, the amounts not being known to the analyst. 



22 Mem. d. Accad. d. Scienze, Bologna, [4] 1, 299 (1882) ; ref., Gazz. Chim. Ital., 

 12,558(1882). 



23 Ann. Chem. u. Pharm., 158, 32(3 (1871). 



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