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 genate. Thus, the combination of Sulphur with potash, or fixed vegetable alkali, is called sulphuret of potash; that which it forms with ammoniac, or volatile alkali, is termed sulphuret of ammoniac. Hydrogen is likewise capable of combining with many combustible substances. in the state of gas, it dissolves charcoal, Sulphur, phosphorus, and several metals; we distinguish these combinations by the terms, carbonated hydrogen gas, sulphurated hydrogen gas, and phosphorated hydrogen gas. The sulphurated gas was called hepatic air by former chemists, or foetid air from sulphur, by Mr Scheele. The virtues of several mineral waters, and the foetid smell of animal excrements, chiefly arise from the preference of this gas. The phosphorated hydrogen gas is remarkable for the property, discovered by Me Gengembrem of taking fire spontaneously upon getting into contact with atmospheric air, or, what is better, with oxygen gas. This gas has a strong flavor, resembling that of putrid fish; and it is very probable that he phosphorescent quality of fish, in the state of putrefaction, arises from the escape of this species of gas. When hydrogen and charcoal are combined together, without the intervention of caloric, to bring the hydrogen into the state of gas, they form an oil, which is either fixed or volatile, according to the proportions of hydrogen and char-