1908.] Experiments with Calcium Cyanamide. 653 



same time does either the cyanamide or the superphosphate 

 suffer any loss of fertilising value ? 



At the outset it should be borne in mind that calcium cyana- 

 mide is slowly attacked by water or by moist air and is con- 

 verted into ammonia and calcium carbonate, roughly in 

 accordance with the equation — 



CaCN 2 + 3H 3 0 = CaCOs + 2NH 3 . 

 There is, however, in the commercial fertiliser a considerable 

 amount of quicklime, which absorbs water and becomes 

 slaked lime in the usual way ; this slaking of the free lime 

 being the first action that takes place when the crude cyana- 

 mide is exposed to moisture. Once the cyanamide has been 

 decomposed there is nothing that will retain the ammonia 

 produced except any excess of moisture that may be present, 

 hence there is always a possibility of loss of the valuable part 

 of the manure, the ammonia, if it is exposed too long to the 

 air ; in the soil the ammonia would, of course, be immediately 

 absorbed by the humus or the clay. 



The action of acids upon the crude cyanamide is similar ; 

 a compound of the acid with the quicklime is at once produced 

 with considerable evolution of heat, then the cyanamide is 

 attacked to form compounds of lime and ammonia with the 

 acid in question. 



Experimental. — A quantity of calcium cyanamide was 

 supplied to the Rothamsted Experimental Station by the 

 North- Western Cyanamide Company, who are establishing 

 large works in Norway for the manufacture and supply of the 

 manure to north-western Europe. The sample in question 

 came from the works at Piano d'Orte in Italy, where the 

 process is now being carried out on a large scale. It con- 

 tained, as a mean of several analyses, 17-24 per cent, of nitro- 

 gen, and was the usual fine black powder, which had been 

 treated by some special process before export, in order to render 

 it less hygroscopic and easier to handle. 



(1) Absorption of water, &c, on exposure, — A series of small 

 quantities (1 gram) of cyanamide was weighed out on watch 

 glasses and placed under a large bell jar over water, thus 

 ensuring the maximum exposure of a thin layer of the manure 

 to the action of moist air. At weekly intervals two watch 

 glasses were withdrawn, and one was weighed in the wet 



