Dry stannous oxide, if touched with a glowing body, catches fire and burns to stannic oxide, Sn02.
In opposition to stannous chloride, even sulphurous acid (solution) behaves as an oxidizing agent.
If it is evaporated slowly, anhydrous stannous oxide crystallizes out in forms which are combinations of the cube and dodecahedron.
According to Stolba, beautiful crystals of pure tin can be obtained as follows: A platinum basin, coated over with wax or paraffin outside, except a small circle at the very lowest point, is placed on a plate of amalgamated zinc, lying on the bottom of a beaker, and is filled with a solution of pure stannous chloride.
Stannous Fluoride, SnF 2, is obtained as small, white monoclinic tables by evaporating a solution of stannous oxide in hydrofluoric acid in a vacuum.
Hence all tin crystals as kept in the laboratory give with water a turbid solution, which contains stannic in addition to stannous chloride.
A mixture of stannous and stannic chloride, when added to a sufficient quantity of solution of chloride of gold, gives an intensely purple precipitate of gold purple (purple of Cassius).
Tin forms two well-marked series of salts, in one of which it is divalent, these salts being derived from stannous oxide, SnO, in the other it is tetravalent, this series being derived from stannic oxide, Sn02.
Traces of bismuth may be detected by treating the solution with excess of tartaric acid, potash and stannous chloride, a precipitate or dark coloration of bismuth oxide being formed even when only one part of bismuth is present in 20,000 of water.
Copper quadrantoxide, Cu 4 0, is an olive-green powder formed by mixing well-cooled solutions of copper sulphate and alkaline stannous chloride.