Acetylene and other terminal alkynes (1-alkynes) are weakly acidic in character.
They react with strong bases like NaNH2 ( sodium in liquid ammonia) to form sodium acetylide derivatives known as acetylides or alkynides.
Acytelene reacts with Na and LI liberating H-2 gas and forming metal acetylide. Therefore acetylene has chemical behaviour similar to acids.
Heavy metal ions mainly, Ag+ and Cu+ react with acetylinic hydrogen (hydrogen atom in acetylene) to form insoluble acetylides.