Don't know why you're being downvoted when you have provided the answer.
"In their search for a new process for producing cyanides for cyanide leaching of gold, Frank and Caro discovered the ability of alkaline earth carbides to absorb atmospheric nitrogen at high temperatures."
Nitrogen is obtained either by fractional distillation of liquid air, or by means of the copper oxide process. In the latter, air is passed through a red-hot mass of finely divided copper, suspended in asbestos or other inert material. The copper combines with the oxygen and allows the nitrogen to pass through. The copper oxide is easily recovered for use by reduction in situ with a suitable gas, such as natural gas.
The nitrogen used must be pure and dry, otherwise, at high temperatures, there is destruction of the carbon pencils, and of calcium carbide, according to the following reactions ...
"In their search for a new process for producing cyanides for cyanide leaching of gold, Frank and Caro discovered the ability of alkaline earth carbides to absorb atmospheric nitrogen at high temperatures."