Prep. By treating sulphuret of iron with dilute sulphuric acid, and passing the gas which is evolved into cold distilled water.

Prop. & Comp. A colourless liquid, having the odour of rotten eggs; gradually decomposing, especially when exposed to air and light, with the deposition of sulphur. It is a watery solution of hydrosulphuric acid, or sulphuretted hydrogen (HS).

Uses. Used only as a test. It possesses the property of throwing down most of the ordinary metals from acid solutions: the precipitate with arsenic is yellow; with antimony, orange; with cadmium, yellow; with mercury, lead, copper, and silver, black; with bismuth and gold, brownish-black, etc. Zinc is precipitated white, from a slightly alkaline solution.

Sulphuretted hydrogen is a constituent of some mineral waters. When the gas is inhaled undiluted, it acts as a poisonous sedative.