Mr. R. C. Campbell on the Ferrocyanides. 513 



the pyroxylic spirit, which has been treated with both quick- 

 lime and chloride of calcium, is burned in a platinum capsule 

 till fully one-half be consumed, the residuum becomes oily 

 and opalescent. 



The spirit used for the construction of the following table 

 was purified by distillation from pulverized quicklime, and 

 was drawn over with the heat of a water-bath, at such a tem- 

 perature that its specific gravity at 60° was 0'8136. When 

 the specific gravity becomes 0'84-7 by the dissipation of the 

 lighter spirit, the boiling point is 14*5° Fahr. I believe that 

 a useful criterion of the nature of pyroxylic spirit would be 

 obtained by comparing its boiling temperatures at different 

 degrees of density. To this point I shall also direct my 

 further investigations. 



The temperature of the pyroxylic spirit when the specific 

 gravities were taken, was exactly 60° Fahr. 



LXXVII. On the Feirocyanides. By [the late] R. Corbett 

 Campbell. Communicated by Dr. Clark*. 



IT is well known that the yellow prussiate of potash, heated 

 * by itself in close vessels, is decomposed into cyanide of 

 potassium, carburet of iron, and nitrogen gas. I have observed 



* Communicated to this Journal by the Chemical Society, having been 

 read June 1, 1841. 



