CYANAMID — MANUFACTURE, CHEMISTRY AND USES II 



crystallize by cooling. It is purified by recrystallization from 

 ether. Yield about 5 grams. 



From Commercial Calcium Cyanamide. — Fresh commercial 

 Cyanamid or better, the unhydrated lime-nitrogen, is extracted 

 with cold water (solubility about 0.9 grams nitrogen in 100 cc. 

 water). The calcium is removed either with oxalic acid or 

 aluminium sulphate, but preferably with the latter. After re- 

 moval of the calcium sulphate and alumina by filtration, the 

 filtrate is evaporated in vacuo below 40°, and the residue ex- 

 tracted with ether. It can be purified by recrystallization from 

 ether. 



PROPERTIES OF CYANAMIDE. 



Cyanamide,^ CN.NHg, most probably has the formula 



C <^ , although in a very few reactions it seems to act as 



if it were carbodiimide, CZ . It is a colorless, crystal- 



line solid, which melts at 41-42° C, as usually prepared. It 

 can be undercooled to 12° without solidifying. On stirring 

 with a sharp-pointed glass rod the undercooled liquid freezes. 

 The carefully purified substance melts sharply at 46° C.^ It 

 is easily soluble in water, alcohol and ether, and is volatile in 

 steam. It is slightly soluble in carbon disulphide, chloroform 

 and benzol. 



Action of Heat. — Pure cyanamide is perfectly stable at ordi- 

 nary temperatures, but polymerizes slowly on heating above 

 its melting point. Impure cyanamide polymerizes slowly at 

 ordinary temperatures. The principal polymer is dicyandia- 



mide, NH : C< >CN, or (H^CNJ,, which is probably 



cyan-guanidine. By strong heating, other derivatives are 



^ Sidgwick, Organic Chemistry of Nitrogen, p. 216, (Oxford, 1910). 

 2 G. Henschel, Diss. Univ. of Leipzig, 191 2. 



