340 alkaline salts. Chemical Characters. It is easily soluble in water; partly volatilised by heat; and becomes moist on exposure to the air. Constituent Parts. It is a compound of Ammonia, Sulphuric Acid, and Water. Geognostic and Geographic Situations. It occurs among the lavas of ..Etna, and Vesuvius ; in the Solfatara by Puzzaeolo; in the lagunes, near Siena in Tuscany; and on the bottom of a hot spring in Dau- phiny. ORDER IIE