SANGER. — VOLATILE COMPOUNDS OF ARSENIC. 119 



2. A glass flask fitted with tubes like the bell jar was covered 

 on the inside with a paste of gelatine and Schweiufurth green, closed, 

 and allowed to stand. 



3. In a bell jar, fitted as in Exp. 1, was placed a dish containing a 

 paste of Schweiufurth green and water. 



4. In a similar bell jar was placed a dish containing arsenious oxide 

 and water. 



Experiments 1 and 2 should decide whether an arsenical gas could 

 be given off by decomposition of an arsenic compound with organic 

 matter aud moisture, while Experiments 3 and 4 would show if any 

 came from an arsenic compound and water alone. In Experiment 1 

 there was soon a formation of mould and odor of mould, and in Ex- 

 periment 2 an odor of decaying gelatine. No garlic smell was noticed 

 iu either. The temperature was 17 to 18°. 



Jar No. 1 and flask No. 2 having been closed for three weeks, 

 at the end of that time the air from the former was led for 24 hours 

 through an absorption bottle containing 150 c. c. water, the air in the 

 jar being renewed about a hundred times. The water was then intro- 

 duced into a flask containing zinc and acid, from which hydrogen had 

 been passing into argentic nitrate for one hour without result. The 

 silver solution was discolored in 15 minutes, and after an hour was 

 completely black. The filtrate became cloudy on addition of ammonia, 

 but was not tested further for arsenic, the black precipitate being 

 considered sufficient indication of the formation of arseuiuretted hy- 

 drogen. The same result was obtained from Experiment 2. 



Jars 3 and 4 were closed for eight days aud the air from them drawn 

 through water as before. The solution from No. 3 gave a very weak 

 action on the argentic nitrate, while that from No. 4 gave none at all. 



The first jar and the flask were again closed for some time and the 

 air led through 150 c.c. of argentic nitrate (1-100). The air, before 

 entering the two vessels, passed through a tube of calcic chloride, and 

 between the jar and the argentic nitrate was placed an empty tube to 

 catch dust or anything that might be condensed. No dust or moisture 

 was noticed in this tube. A slight gray deposit was formed in the 

 silver solution and the filtrate gave a turbidity with ammonia. 



From the fact that the color of the paper was not lessened, Fleck 

 concludes that the Schweinfurth green was not decomposed, but that 

 the formation of arseniuretted hydrogen was due to decomposition of 

 arsenious oxide. From the amount of silver precipitated Ire reckons 

 the amount of hydride formed at 0.01 c. c. in the five litres. 



Fleck also mixed five grams arsenious oxide with two grams starch 



