Ammonium sulfide, also known as diammonium sulfide, is an unstable salt with the formula (NH₄)₂S. Aqueous solutions purporting to contain this salt are commercially available. With a pK_a exceeding 15, the hydrosulfide ion cannot be deprotonated to an appreciable amount by ammonia. Thus, such solutions mainly consist of a mixture of ammonia and (NH₄)SH. Ammonium sulfide solutions are used occasionally in photographic developing, to apply patina to bronze, and in textile manufacturing. Also, due to its offensive smell, it is the active ingredient in a variety of foul pranks including the common stink bomb.