A System of Instruction in the Practical Use of the Blowpipe Part 13

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves in large quant.i.ties to a clear colorless gla.s.s.

in the reducing flame.

If the acid be not present in too large a proportion, the gla.s.s remains unchanged. An additional amount of the acid renders it violet, and a still larger quant.i.ty affords a beautiful pure blue color, similar to that produced by tungstic acid. If to such a bead some sulphate of iron be added, the gla.s.s becomes blood-red. The addition of peroxide of iron renders the gla.s.s deep yellow while warm, the color becomes paler on cooling.

27. Pelopic Acid, Pp^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Behaves similarly to the preceding.

in the reducing flame.

A bead containing sufficient of the acid to render it spontaneously opaque on cooling, has a greyish color.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves even in large quant.i.ty to a colorless gla.s.s.

in the reducing flame.

With sufficient dose of the acid, the bead becomes brown with a violet tinge. This reaction is readily obtained upon charcoal.

Sulphate of iron renders the bead blood-red.

28. Oxide of Antimony, SbO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Even when in large proportion, dissolves to a clear gla.s.s, which is yellow when warm, but almost entirely loses its color on cooling. On charcoal, the antimonious acid may be almost expelled, so that tin produces no further change.

in the reducing flame.

A bead, that has only been treated for a short time in the oxidizing flame, when submitted to the reducing flame becomes grey and turbid from the reduced antimony. This soon volatizes and the gla.s.s again becomes clear. The addition of tin renders the gla.s.s ash-grey or black, according to the amount of oxide it contains.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves with ebullition to a gla.s.s of a pale yellow color while warm.

in the reducing flame.

On charcoal, the saturated gla.s.s becomes at first dull, but as soon as the reduced antimony is volatilized, it again becomes clear. With tin, the gla.s.s is at first rendered grey by the reduced antimony, but by continued blowing is restored to clearness. Even when the gla.s.s 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 gla.s.s. 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 quant.i.ty, the gla.s.s undergoes no change. With a larger proportion, the gla.s.s is deep yellow while warm, and yellowish-brown when cold. This reaction takes place upon charcoal, with a small quant.i.ty of the acid. Tin produces a dark coloration, when the acid is not present in too great a quant.i.ty.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves to a clear gla.s.s, which, when saturated, is yellow in the hot state.

in the reducing flame.

The gla.s.s is of a pure blue. If the tungstic acid contain iron, the gla.s.s becomes blood-red on cooling, similar to t.i.tanic acid.

In this case, tin restores the blue color, or, if iron be in considerable quant.i.ty, renders it green.

30. Molydbic Acid, MO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves readily and in large quant.i.ty. When but little is dissolved, the gla.s.s is yellow while hot and colorless when cold. When in larger quant.i.ty 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 gla.s.s, which has been treated in the oxidizing flame, becomes, when the acid is not present in too large a quant.i.ty, brown, and when in large quant.i.ty, perfectly opaque. In a strong flame, oxide of molybdenum is formed which is visible in the yellow gla.s.s in the form of black flakes. If the gla.s.s appear opaque, it should be flattened with the forceps.

Behavior with Mic. Salt on Platinum wire