656 



Experiments with Calcium Cyanamide. [feb., 



beneath was saturated and a considerable loss of material took 

 place. 



It may be concluded that while calcium cyanamide will 

 gradually slake and swell, and suffer a small loss of ammonia 

 on exposure to damp air in bags, yet under ordinary working 

 conditions these losses will be inappreciable, and the manure is 

 no more difficult to store than other artificial manures used 

 by the farmer. 



(2) The manufacturers state that they now take special 

 precautions to leave no unaltered carbide in their product, 

 so that the evolution of acetylene from the cyanamide which 

 was noticed with some of the earlier products no longer takes 

 place. 



To test the point a current of air saturated with moisture 

 by bubbling through water was led over 20 grams of cyanamide 

 in a flat-bottomed flask and then through a washing bottle 

 containing a solution of ammoniacal silver nitrate of known 

 strength. Blackening of the silver solution slowly took place, 

 and after the air current had been continued for seven days 

 the solution was examined. A very small amount of black 

 precipitate was recovered, and this on testing proved to contain 

 silver acetylide, silver sulphide and a trace of phosphide ; 

 the amount recovered was, however, too small for analysis. 

 Assuming that it had all been precipitated by acetylene 

 and calculating from its weight back to calcium carbide the 

 original crude cyanamide contained : — 



Experiment I. — cro48 per cent, calcium carbide. 

 2.-0-062 ,, 



quantities which are negligible. 



In another experiment 20 grams of cyanamide were shaken 

 into a large bottle with a little water, and the bottle stoppered 

 and put aside for a day in a warm place. The bottle was then 

 carefully opened and a light introduced; the taper burnt 

 quietly because not enough inflammable gas had been generated 

 to produce an explosive mixture. Since the exposure in both 

 the above experiments was much more severe than could 

 obtain in practice it may safely be concluded that the traces of 

 acetylene, sulphuretted hydrogen and phosphine that will be 

 obtained from the crude cyanamide can be neglected, for they 

 will never become a source of danger Or even inconvenience. 



