Barium, Oxide of

BaO. Syn. Baryta , Bary′tes , Cau′stic baryta* , Ox′ide of ba′′rium , Protox′ide of b. , Heav′y earth ; Baryte , Oxide de barium , Terre pesante† , ., Fr.; Baryt , Baryterde , Schwererde , ., Ger. One of the earths discovered by Scheele in 1774. Sources. Sulphate and carbonate of barium are abundant minerals, forming the ‘vein-stone’ of many lead mines. It is from the latter that baryta and the barium salts are almost exclusively obtained. Prep. 1. A mixture of carbonate of barium and charcoal (both in fine powder and moistened) is strongly ignited, for some time, in a porcelain, He ian, or black-lead crucible, and then allowed to cool out of contact with the air, from which it must also be subsequently carefully preserved. 2. (Pure.) Crystallised nitrate of barium is calcined in a capacious covered porcelain or He ian crucible, at a bright red heat, until red (nitrous) vapours are no longer disengaged, even on raising the temperature; and the residuum, as soon as the temperature has fallen sufficiently, but whilst still warm, is at once transferred to a bottle, as before. 3. M. Rosenthiel’s proce is founded upon the decomposition of sulphide of barium di olved in boiling water by oxide of zinc. Caustic baryta and sulphate of zinc are formed. Prop. A greyish-white, spongy, earthy-looking ma , fusible only before the oxyhydrogen blowpipe; highly caustic, corrosive, and alkaline, and slaking, like quick-lime, on the addition of water, but with the evolution of more heat.