Barium Cyanamide, BaCN₂

The formation of Barium Cyanamide, BaCN₂, along with cyanide by the action of nitrogen on barium carbide has already been mentioned. Absorption readily takes place at 700°-800° C. A mixture of barium carbonate, or oxide, and carbon can be substituted for the carbide. Absorption then begins a little above 900° C. It is favoured by the presence of calcium chloride, and addition of barium chloride seems to facilitate it a little at low temperatures, but to decrease it at high. On the whole, barium chloride decreases the proportion of cyanamide.

There seems to be doubt as to the effect of temperature on the relative proportions of the two substances formed. According to Kuhling and Berkhold the proportion of cyanamide decreases with rise of temperature, but Ewan and Napier found that fusion of barium cyanide results in the formation of barium cyanamide, the amount of the latter depending on the duration and temperature of heating, the presence of finely divided iron also increasing the proportion of cyanamide. This supports the statement of Askenasy and Grude that at 1300°-1400° C. cyanide is first formed, and this at still higher temperatures gives cyanamide, the latter process being also favoured by a shortage of carbon. The equilibrium can no doubt be approached from either side, but the variation in the position of equilibrium with temperature has apparently not been very carefully studied. Fusion of the cyanide-cyanamide mixture with potash or soda also converts the whole into cyanide.

Barium cyanamide may also be obtained by fusing barium cyanate. By passing carbon dioxide into an aqueous solution of barium cyanamide, prepared by dissolving barium hydroxide in a solution of cyanamide, filtering, and adding more cyanamide, a heavy, granular, crystalline precipitate of composition 2(BaCN₂.CO₂).3H₂O is readily obtained.