The fact that only a portion of the nitrogen in zinc dust is 

 removed by heat indicates that the nitrogen is present in more 

 than one form. This theory is also supported by the following 

 experiments : 



A fresh sample of zinc dust was washed with water ,the 

 washings giving a decided ammonia test. The washing was 

 continued as long as traces of nitrogen could be detected in the 

 washings. It was then treated in the same manner with very 

 dilute hydrochloric acid. By adding potassium hydroxide in ex- 

 cess to the acid solution and allowing to stand a few minutes un- 

 til the precipitate settled, decanting the clear solution and boil- 

 ing, the vapors gave the odor of ammonia and rapidly changed 

 litmus from red to blue. Washing with acid was continued until 

 the washings no longer gave a test for nitrogen. The zinc was 

 then washed with water until free from acid, and rapidly dried 

 in a drying oven, and at once extracted with ether, the ether 

 evaporated and tested for nitrogen as above. Nitrogen was found 

 to be present, though not in as large amounts as in the oil from 

 the first sample examined, which was, however, directly treated 

 with ether. 



Three samples were examined : one from a large closely 

 covered can which had been in use in the laboratory as above 

 stated ; another from a glass bottle which had been in the museum 

 about fifteen years, and a third which was ordered by Professor 

 Oesterle for these experiments. Practically the only difference 

 found in the three samples was that the oil from the fresh sample 

 was decidedly yellow, while that from the laboratory sample was 

 somewhat lighter, and that from the museum sample was colorless. 



Dr. Victor Steger ("Metalldampfe in Zinkhiitten," Chem- 

 ischer und Chemischtechnischer Vortrage) gives the results of 

 several analyses of zinc dust, some of which contain considerable 

 insoluble residue consisting principally of carbon. To determine 

 to what extent this was present, a large amount of zinc dust 

 was treated with hydrochloric acid. At first the reaction was 

 rapid, but after a time ceased. The solution was decanted and 

 fresh acid added, but as the reaction was very weak the mixture 

 was heated. Even then a large amount remained undissolved. 

 A few drops of copper sulphate solution were added and digested 

 for several days, but a large amount remained insoluble. This 

 was washed with water until free from acid, dried, and per- 



