676 Ford and Bradley — Footeite and Connellite. 



to obtain it by artificial means but with only negative results. 

 The authors gratefully acknowledge the advice of Prof. H. 

 W. Foote in regard to this portion of the investigation. 



A large number of tests were made upon specimens of ata- 

 camite, brochantite and other similar minerals in order to ascer- 

 tain if they might not also contain small amounts of nitric 

 oxide which had previously been overlooked. In only one 

 case, however, was any evidence of its presence discovered. 

 A solution of an atacamite from the United Verde mine, 

 Jerome, Arizona, gave a faint color reaction with diphenyla- 

 mine, indicating the presence of a trace of nitric acid. 



Mineralogical Laboratory of the Sheffield Scientific School of Yale 

 University, New Haven, Conn., April 12, 1915. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Fixation of Atmospheric Nitrogen. — In an address 

 delivered recently before two sections of the American Chemical 

 Society, W. S. Landis has discussed this important topic, giving 

 special attention to the calcium cyanamide industry at Niagara 

 Falls. It is well known that the first step of this process is the pro- 

 duction of calcium carbide, CaC 2 , from lime and coke in an elec- 

 tric furnace. This product is then finely ground and heated with 

 atmospheric nitrogen in order to form a mixture of calcium cyana- 

 mide, CaCN 2 , and free carbon. The magnitude of the operation 

 may be perceived from the statement that 2,000,000 cubic feet of 

 practically pure nitrogen (or about 15 tons) are used daily for this 

 purpose at Niagara Falls. The crude cyanamide contains about 

 22 per cent of nitrogen, and it is used as a fertilizer, after being 

 ground, treated with a little water to decompose any unaltered 

 calcium carbide, and oiled to prevent the formation of dust. At 

 present this appears to be the chief use of the cyanamide, but it 

 may be used for several other purposes. For instance, when 

 mixed with water and heated under pressure its nitrogen is all 

 converted into ammonia according to the equation CaCN 2 + 

 3H 2 = 2NH 3 + CaC0 3 . Another transformation is effected by 

 melting down a special grade of cyanamide with a flux, such as 

 common salt, when the free carbon present combines with the 

 cyanamide forming cyanide. The resulting product is equiva- 

 lent to about 25 per cent of its weight of potassium cyanide, and 

 it is stated that this crude form of cyanide is perfectly service- 

 able in the metallurgical operation of extracting gold and silver 

 from ores, and is very much cheaper than the higher grade 



