SANGER. VOLATILE COMPOUNDS OP ARSENIC. 123 



passed a stream of hydrogen from sodium amalgam over a quantity of 

 wall paper, free from arsenic and antimony, contained in a large glass 

 vessel, and directed the stream against paper moistened with argentic 

 nitrate and screened from light. There was no action after 12 hours, 

 nor did the addition of ammonia to the hydrogen cause any blacken- 

 ing. He then passed ammoniacal hydrogen from sodium amalgam 

 over moist paper containing a large quantity of arsenic, and obtained 

 what he calls "characteristic reactions " for arsenic, probably a reduc- 

 tion of the silver paper. Of course the blackening of paper cannot be 

 taken as proof of the presence of arseniuretted hydrogen, nor is the 

 formation under these conditions to be expected. Bartlett notes that 

 he intends to pass ammoniacal hydrogen over 20 sq. yd. of paper for 

 a long time in the hope of collecting the resulting argentic arsenite, 

 but he has not, to my knowledge, published anything further on this 

 subject. 



Forster,* in 1880, tried the following experiments to ascertain 

 whether arsenious oxide was volatilized from Scheele's green, and 

 whether arseniuretted hydrogen could be given off from a paint con- 

 taining this pigment. Air was drawn through a bottle filled with glass 

 covered with Scheele's green, and, after filtration by cotton wool, was 

 passed into a solution of potassic hydroxide. One experiment lasted 

 one day, two lasted two days each, and a fourth seven days, the tem- 

 perature of the bottle being from 45 to 50°. In each case the potassic 

 hydroxide was neutralized by sulphuric acid, and by the Marsh method 

 gave no arsenic. In a second series the bottle was filled with shavings 

 smeared with a paint of linseed oil, turpentine, and Scheele's green. 

 The air was not filtered and passed through two U tubes containing 

 potassic hydroxide and argentic nitrate respectively. Two trials were 

 made for five days and two for six days, at a temperature of 14° ; a 

 fifth lasted nine days. The potassic hydroxide solution, treated as 

 before, gave no arsenic. The silver solution was precipitated by 

 hydrochloric acid, and sulphuretted hydrogen led through the filtrate 

 for twelve hours. Not getting a precipitate, Forster concludes the 

 absence of arsenic, but tests further by the Marsh method with a 

 negative result. 



Giglioli,t in 1880, after a series of experiments lasting eight 

 months, declared himself opposed to the theory of Selmi, and favored 



* Proceedings Med. Soc. of London, V. 41 ; Chemical News, 1880. 

 t Ann. d. R. Scuola sup. d' Agricoltura di Portici, II. 165; Gazz. chim. Ital., 

 1881, p. 249. 



