Note 56 — Chapter XIV · THE VALENCY AND SPECIFIC HEAT OF THE METALS. MAGNESIUM. CALCIUM, STRONTIUM, BARIUM, AND BERYLLIUM
George Kamensky translation
The property of barium oxide of absorbing oxygen when heated, and giving the peroxide, BaO2, is very characteristic for this oxide (see Chapter III., Note 7). It only belongs to the anhydrous oxide. The hydroxide does not absorb oxygen. Peroxides of calcium and strontium may be obtained by means of hydrogen peroxide. Barium peroxide is insoluble in water, but is able to form a hydrate with it, and also to combine with hydrogen peroxide, forming a very unstable compound having the composition BaH2O4 (obtained by Professor Schöne), which in course of time evolves oxygen (Chapter IV., Note 21).