A System of Instruction in the Practical Use of the Blowpipe Part 14

in the oxidizing flame.

Dissolves to a clear gla.s.s, which, when sufficient acid is present, is of a yellowish-green color when warm, and becomes nearly colorless on cooling. On charcoal, the gla.s.s becomes dark, and when cool has a beautiful green color.

in the reducing flame.

The gla.s.s becomes of a bottle-green color, which on cooling, changes to a brilliant green, similar to that produced by oxide of chromium. The reaction on charcoal is precisely similar. Tin renders the color somewhat darker.

31. Vanadic Acid, VaO^{8}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves to a clear gla.s.s, which is colorless when only a small quant.i.ty of acid is present, and yellow when containing a larger proportion.

in the reducing flame.

The yellow color of the gla.s.s changes to a brown when warm and a chrome-green on cooling.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax.

in the reducing flame.

As with borax.

32. Oxide of Chromium, Cr^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Affords an intense color, but dissolves slowly. A small proportion colors the gla.s.s yellow when warm, and yellowish green when cold; a larger addition produces a dark red color when warm, which, on cooling, becomes yellow and finally a brilliant green with a tinge of yellow.

in the reducing flame.

A small quant.i.ty of the oxide renders the gla.s.s beautifully green both when warm and when cold. A larger addition changes it to a darker emerald green. Tin produces no change in the color.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves to a clear gla.s.s which has a pink tinge while warm, but on cooling becomes dusky green, and finally brilliantly green.

in the reducing flame.

As in the oxidizing flame, except that the colors are somewhat darker. Tin produces no further change.

33. a.r.s.enious Acid, AsO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

No reaction.

in the reducing flame.

No reaction.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

No reaction.

in the reducing flame.

No reaction.

34. Tellurous Acid, TeO^{2}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves to a clear colorless gla.s.s which, when treated on charcoal, becomes grey and dull from particles of reduced tellurium.

in the reducing flame.

As in the oxidizing flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax.