Ammonium pentasulfide is a chemical compound with the chemical formula .
Passing hydrogen sulfide through a suspension of powdered sulfur in a concentrated ammonia solution:
Ammonium sulfide forms yellow crystals, decomposing in water, of monoclinic system, space group P2<sub>1</sub>/c, cell parameters a = 0.5427 nm, b = 1.6226 nm, c = 0.9430 nm, ò = 105.31ð, Z = 4.
The compound can be stored under the mother liquor without air access. When dry, it decomposes quickly in the air. the compound emits sulfur intensively in water and melts in a sealed ampoule at 95 ðC to form a red liquid.
The compound decomposes when stored in air or slightly heated: