SANGER. — VOLATILE COMPOUNDS OF ARSENIC. 1*25 



through the flask and system of tubes at the rate of 15-23 litres daily. 

 Mould was noticed in 16 days. From June 4, 187G, to November 21, 

 1885, the air of the flask was tested at irregular intervals, as detailed 

 below, and the presence of arsenic in the silver solutions determined. 

 Li every solution except the first, reduction of the silver was noticed, 

 and very often a yellowish sediment was formed. The odor of the 

 air in the flask was very disagreeable, and in one case brought to 

 mind the odor of either arseniuretted hydrogen or kakodyl. Sometimes 

 the silver solution had a strong odor. Argentic nitrate paper, hung 

 in the flask, turned dark very quickly, but plumbic acetate paper was 

 not affected. Auric chloride paper was introduced in the last year, 

 but was not reduced. Ammonia was given off freely, especially 

 towards the last. 



November 21, 1885, as the last silver solution tested gave but a 

 faint deposit in the reduction tube, and an argentic nitrate paper 

 hung in the flask was not blackened, it was concluded that the action 

 had ceased. The residue in the flask was then examined for arsenic. 

 An aqueous extract yielded 149 mgr. arsenious sulphide and the 

 residue from this, extracted with very dilute acetic acid gave 67 mgr. 

 The remainder of the mass, consisting of organic matter, earth, sand, 

 etc., was treated with hydrochloric acid and potassic chlorate, and 

 from the filtered solution 469 mgr. arsenious sulphide were obtained, 

 making 685 mgr. in all, corresponding to 551 mgr. arsenious oxide. 

 The residue from the treatment with hydrochloric acid and potassic 

 chlorate was not examined further, and it is quite possible that the 

 extraction was not complete. 



The arsenic was found in the first two extracts as arseniate, but a 

 similar condition could not from the method of extraction be shown 

 in the residue. Undoubtedly the lower oxide was to a great extent 

 changed to the higher. Hamberg concluded that the remaining 449 

 mgr. had passed away as some gaseous compound, though it is not to 

 my mind certain that these figures are not too large by the amount 

 which may have remained in the last residue. 



A consideration of the amount actually absorbed is interesting, and 

 throws some light on the nature of the volatile compound. In the 

 interval between two successive examinations of silver solutions, 

 or when the flask was opened to test odor or action on test paper, 

 much of the gas may have escaped, yet it can be fairly assumed that 

 most of it came in contact with the absorbents. In the first examina- 

 tion (after a run of five months) there were found 1.1 mgr. of arsenious 

 sulphide, corresponding to 0.88 mgr. of the oxide. In the second test 



