On charcoal, the saturated glass becomes at first dull, but as soon as the reduced antimony is volatilized, it again becomes clear. With tin, the glass is at first rendered grey by the reduced antimony, but by continued blowing is restored to clearness. Even when the glass contains but little oxide, tin produces this reaction. * * * * * 29. Tungstic Acid, WO^{3}. Behavior with Borax on Platinum wire in the oxidizing flame. Dissolves readily to a clear colorless glass. In large proportion it renders the borax yellow, while warm, and with a still greater addition the bead may be made opaque with an intermittent flame. If more be then added, this reaction takes place spontaneously. in the reducing flame. When the oxide is present in small quantity, the glass undergoes no change. With a larger proportion, the glass is deep yellow while warm, and yellowish-brown when cold. This reaction takes place upon charcoal, with a small quantity of the acid. Tin produces a dark coloration, when the acid is not present in too great a quantity. Behavior with Mic. Salt on Platinum wire in the oxidizing flame. Dissolves to a clear glass, which, when saturated, is yellow in the hot state. in the reducing flame. The glass is of a pure blue. If the tungstic acid contain iron, the glass becomes blood-red on cooling, similar to titanic acid. In this case, tin restores the blue color, or, if iron be in considerable quantity, renders it green. * * * * * 30. Molydbic Acid, MO^{3}. Behavior with Borax on Platinum wire in the oxidizing flame. Dissolves readily and in large quantity. When but little is dissolved, the glass is yellow while hot and colorless when cold. When in larger quantity yellow while warm and opaline when cold, and a further addition of acid renders it yellow when warm, the color, on cooling, changing first to a pale enamel blue, and then to an enamel white. in the reducing flame. The glass, which has been treated in the oxidizing flame, becomes, when the acid is not present in too large a quantity, brown, and when in large quantity, perfectly opaque. In a strong flame, oxide of molybdenum is formed which is visible in the yellow glass in the form of black flakes. If the glass appear opaque, it should be flattened with the forceps. Behavior with Mic. Salt on Platinum wire in the oxidizing flame. Dissolves to a clear glass, which, when sufficient acid is present, is of a yellowish-green color when warm, and becomes nearly colorless on cooling. On charcoal, the glass becomes dark, and when cool has a beautiful green color. in the reducing flame.