138 



CALCIUM CYANAMIDE 



temperature is kept low, the yield of sulphate may amount to three or 

 four times that just given. 



The magnitude of the ammonium sulphate manufacture may be 

 judged from the following table, which gives the production, in tons, in 

 the United Kingdom during the years 1899, 1907, 1908 and 1909 l : 



In 1910, the total production of this country was 367,587 tons. 



In 1909, 264,000 tons of sulphate of ammonia were exported, leav- 

 ing about 85,000 tons for home consumption. In 1908, the figures 

 were 235,000 and 90,000 tons, respectively. 



If a successful method of utilising the sulphur, always present 

 in coal, in the formation of sulphuric acid, could be devised, a further 

 cheapening of sulphate of ammonia would result. The price of sul- 

 phate of ammonia varies considerably, but is usually about 12s. per cwt. 



Calcium Cyanamide. This substance was prepared by Franck 

 and Caro in 1895, by the action of nitrogen upon strongly heated 

 calcium carbide. It was first used as a manure in 1901. 



The reaction involved in its production is simple : 



calcium carbide and nitrogen yielding calcium cyanamide and free 

 carbon. The temperature required is said to be about 1000 C. and 

 the nitrogen is obtained from the air by removal of oxygen, either by 

 means of heated copper, or by fractional distillation of liquid air. It 

 is said that the addition of a small quantity of calcium chloride to the 

 calcium carbide, enables the reaction to occur at a lower temperature 

 (Polzeniusz). 



A similar product is formed when lime or chalk is heated with coke 

 or coal to a temperature of 2000 in a current of air. 



Two forms of calcium cyanamide were put on the market one 

 prepared by the Caro and Franck process known as " Kalk-stickstoff " 

 or "lime nitrogen" the other by the Polzeniusz process, known as 

 " Stickstoffkalk " or " Nitrolime " or " Nitrolim ". 



Many factories for its production have been erected and a consider- 

 able trade has already been established. Works in Italy, Dalmatia, 

 France, Switzerland, Germany, Norway, Japan, and near Niagara are 

 in operation. The commercial product is a fine, nearly black powder, 



Report of Chief Inspector of Alkali Works, 1910; abstract in Jour. Soc. Chem. 

 Ind., 1910, 942. 



