Stannous Oxide, SnO

Stannous Oxide, SnO, may be prepared in several ways. It is obtained by heating a mixture of stannous chloride and sodium carbonate until it becomes black, then washing with water, and drying the residue with a gentle heat in a stream of carbon dioxide. It is also produced by igniting stannous oxalate out of contact with air, when it is obtained as an olive-green powder; and by precipitating stannous chloride solution with alkali, and boiling the hydrated oxide thus produced with dilute caustic potash solution; the anhydrous oxide thus formed crystallises in microscopic cubes or octahedra. A crystalline form of the oxide is also obtained by digesting a nearly saturated solution of stannous oxide in acetic acid of density 1.06 at 56° C. This form of the oxide is red, but quiokly turns black on exposure to sunlight.

The black amorphous oxide easily dissolves in hydrochloric acid forming stannous chloride, and burns when heated in the air forming the dioxide:

SnO(cryst.) + ½O₂ = SnO₂(cryst.) + 71,000 calories.