658 



Experiments with Calcium Cyanamide. [feb., 



the acid calcium phosphate ; the. temperature was, however ? 

 kept down by the evaporation of the surplus water in the 

 superphosphate and might have been still further reduced, had 

 it been thought desirable, by sprinkling a little water over the 

 mass while the mixing was going on. 



To test this point a further experiment was tried in which 

 two separate hundredweights of superphosphate were spread 

 on the floor and 56 lb. of cyanamide was carefully poured on 

 each, covered with the superphosphate and mixed as before. 

 In one case, No. 4, nothing was added to the mixture of two 

 parts superphosphate and one cyanamide, but in the other, 

 No. 5, 2 gallons of water were sprinkled on from a water pot 

 as the mixing went on. This kept the dust down entirely, 

 so that it was possible to complete the mixing without any 

 trouble from the fineness of the cyanamide. The highest 

 temperature reached was 95° (it was a damp cool day with an 

 air temperature of 13 0 C), and the wetted heap ran up to this 

 point more quickly than the unsprinkled heap. This was 

 because 1 cwt. of superphosphate does not contain water 

 enough to slake all the lime in \ cwt. of cyanamide, so that the 

 mixture did not react as strongly as one poorer in cyanamide 

 would have done. Further, with such a small proportion of 

 superphosphate there was not enough acid in it to neutralise 

 all the ammonia produced, consequently a little ammonia 

 could be detected escaping from the steaming heaps both by 

 the nose and by litmus paper. 



These latter trials are quoted here to show that sprinkling 

 with water can be used with advantage while making up a 

 mixture of superphosphate and cyanamide, as it keeps down the 

 dust and restricts the rise of temperature without adding any 

 difficulties to the mixing process or causing the final product 

 to cake or set in any way. In the above experiments the 

 material was friable and in a good working condition on the 

 following day. 



As will be seen from the weights the heat generated caused 

 the evaporation of a good deal of water, so that the heaps 

 had lost weight considerably when they come to be bagged. 

 There was no tendency to cake shown during the mixing, and 

 on the following day, when the heaps had cooled down, the 

 mixture was still perfectly loose and friable, neither has it 



