Hydrogen sulphide (H.28; 34) is obtained by the action of sulphuric acid on pyrites. It is a colorless gas, having a disgusting odor suggesting that of rotten eggs. Its specific gravity is 1.19; water dissolves three times its volume of the gas.

The Solution (acid hydro-sulphuric liquidum, aqua hydro-sulphurate, H. S + 488.7 aq. = 4415.5) is not permanent in the air, but is oxidized, water being formed and white sulphur deposited. The liquid compound has no direct medicinal value. In the manufacture of mineral waters it is used for making "sulphur waters," if no sodium sulphide can be employed. It is never put in the apparatus, but gauged into each bottle, or the required dose separately put up in vials for each bottle, and mixed for immediate consumption, or a separate fountain for sulphur waters exclusively is employed. Acid Sulphuric (H3So4; 98). - The chemically pure acid is a liquid composed of not less than 96 per cent, of absolute sulphuric acid, and not more than 4 per cent, of water. It should be preserved in glass-stoppered bottles. A colorless liquid, of an oily appearance, inodorous, strongly caustic and corrosive, and having a strongly acid reaction. Its specific gravity should not be below 1.840. It is miscible, in all proportions, with water and alcohol, with evolution of heat. Sulphuric acid is used to produce various salts within the combination of artificial mineral waters and to separate silica from sodium silicate.