(1):
A crystalline substance, (C2H4NH)2, formed by action of ammonia on ethylene bromide, by reduction of pyrazine, etc. It is a strong base, and is used as a remedy for gout.
(2):
A feebly basic solid, C4H4N2, obtained by distilling piperazine with zinc dust, and in other ways. Also, by extension, any of various derivatives of the same.