Strontium Peroxide, SrO₂

Similarly to calcium peroxide, Strontium Peroxide, SrO₂, was first obtained as a white crystalline precipitate in the hydrated form, SrO₂.8H₂O, by the action of hydrogen peroxide or sodium peroxide on strontium hydroxide. It is also formed when an alkali reacts with a strontium salt solution containing hydrogen peroxide. By heating to 130° C. in a current of dry air, or by drying in vacuo, the anhydrous compound is obtained, but it cannot be completely freed from water without partial decomposition. The anhydrous peroxide may be prepared directly by precipitating from very concentrated solutions above 50° C. Very large pressures are required in order to make strontium oxide combine directly with oxygen. Combination under a pressure of 76 atmospheres of oxygen is possible, but the maximum yield, 15-16 per cent, of peroxide, is obtained at about 400° C. under a pressure of 98 atmospheres.

The heat of formation from strontium oxide and oxygen is 10.875 Cal., or from metallic strontium and oxygen 153.07 Cal.

At red heat strontium peroxide melts and gives off oxygen. It is a white powder, only slightly soluble in water, by which it is partially decomposed, but soluble in acids. Anhydrous commercial strontium oxide contains 85 per cent, of strontium peroxide and 15 per cent, of strontium hydroxide, and has a density of 0.546. It is very stable in a dry atmosphere, and may be heated to 150° C. without loss of available oxygen.

The octahydrate is precipitated at ordinary temperatures from dilute solutions of strontium hydroxide and hydrogen peroxide. It has been suggested that the compound formed contains 9 molecules of water of crystallisation. The heat of hydration is 20.48 Cal. Hydrates containing 10 and 12 molecules of water have been mentioned.