Note 564 — MANGANESE561.

[The action of peroxide of manganese (the only compound of the metal used in the manufacture of glass) is simple and clearly understood. The sand (silica) used in the manufacture of glass frequently contains iron, which by the heat necessary for the fusion of the glass becomes reduced to the state of protoxide, giving the glass a greenish or yellowish colour; also, if any organic substance be present in the materials (and where sulphate of soda is used, charcoal is added), the glass is not colourless. When peroxide of manganese is added, it parts with some of its oxygen, becoming reduced to the protoxide, which remains colourless in the glass, the protoxide of iron absorbing the oxygen, becomes at the same time converted into the peroxide, which also imparts no colour to the glass, which is thus rendered colourless. If more of the peroxide of manganese be added than the carbon or protoxide of iron can reduce, it will tinge the glass of an amethyst colour, as stated in the text.]