Barium Periodate, Ba(IO₄)₂

Barium Periodate, Ba(IO₄)₂, has not been isolated in the solid state, but several basic salts are known. The compound formed by precipitation of a barium salt by an alkali periodate in acid solution is BaO.Ba(IO₄)₂.7H₂O. If the solution is strongly acid a pentahydrate or, in presence of nitric acid, a trihydrate may be formed. The hepta- hydrate loses 4 molecules of water at 200° C., and is completely dehydrated at 300° C.

Ihre obtained also the compound 2BaO.Ba(IO₄)₂.6H₂O.

By calcination of the dibarium salt, or by heating barium oxide, peroxide, or carbonate with iodine in the presence of air, a pentabarium compound, 4BaO.Ba(IO₄)₂, is obtained. It is also formed by heating barium iodate to a high temperature when iodine and oxygen are evolved, or by heating barium iodide in dry air. Similar reactions take place with calcium and strontium compounds, but the products are less stable. Rammelsberg obtained several other salts of doubtful composition, and Langlois isolated the compound 3BaO.2Ba(IO₄)₂.5H₂O.