328 PROCEEMNGS OF THE AMERICAN ACADEMY. 



was diluted with water and introduced into the Marsh flask. The 

 amount of arsenic was determined by Sanger's ^ modification of the 

 Berzelius-Marsh method. 



In the twenty cases of suspected arsenical poisoning referred to in 

 the above paper, thirty-one samples of urine were examined by this 

 method, and in no instance was the amount of arsenic (as arsenious 

 oxide) greater than 0.07 mg. per liter. The analytical precautions 

 were such as to preclude the introduction of arsenic from any outside 

 source. Prior to these analyses but one instance had been found in 

 which a method for the quantitative estimation of arsenic in urine had 

 been described. Hubbard,^ in studying the elimination of arsenic by 

 the kidneys, added the urine directly to the Marsh flask and deter- 

 mined the weight of the mirror according to the gravimetric Berzelius- 

 Marsh method, first applied by Gautier,^ and afterwards elaborated by 

 Chittenden and Donaldson ^ and others. While the amounts of 

 arsenic found by Hubbard (varying from 0.35 to 1.12 mg. per liter) 

 were undoubtedly a close approximation, the method cannot be applied 

 to minimal amounts with certainty on account of the impossibility of 

 accurately weighing small mirrors and the effect of the presence of 

 organic matter on their deposition. 



The treatment described above has been used by several analysts 7 

 in the determination of arsenic in urine. Unfortunately it was not 

 accurately tested by the analysis of urines containing known amounts 

 of arsenic, partly on account of lack of time, partly through acceptance 

 of the Gautier method. The assumption that all of the arsenic pres- 

 ent was accounted for was probably incorrect, as our present work 

 will show. 



The method is a troublesome one, requiring much time for evapora- 

 tion and the destruction of the organic matter, as care must be taken 

 to have the latter entirely eliminated, since the accurate determination 

 of the arsenic is impossible in its presence. The use of large quanti- 

 ties of nitric acid is unpleasant and may introduce error. These con- 

 siderations, together with the much more important one of possible loss 

 of arsenic, have led us to substitute for the destruction of the organic 

 matter with nitric acid a distillation of the arsenic from the evaporated 

 urine by means of hydrochloric acid. 



3 These Proceedings, 26, 24 (1891) ; Amer. Chem. Jour., 13, 4:31 (1891). 

 * rhysiciau and Surgeon, Ann Arbor, Mich., 4, 348 (1882) ; Contr. Chem. Lab. 

 Univ. Mich., 1, Part I (1882). b Loc. cit. 



6 Amer. Chem. Jour., 2, 235 (1881). 



7 Putnam-Worcester, Bost. Med. Surg. Jour., 124, G23 (1891); Wood, Ibid., 

 128,414 (1893); and others. 



