A metallic carbide on treatment with water gives a colourless gas which burns readily in air and which gives a precipitate with ammoniacal silver nitrate solution. Gas evolved is
Acetylene
CaC2+2H2O→Ca(OH)2+C2H2CH≡CH+2[Ag(NH3)2]OH→ Ag−C≡C−Ag+4NH3+2H2O White ppt.