* * * * *

7.  Oxide of Nickel, NiO.

  Behavior with Borax on Platinum wire

    in the oxidizing flame.

Colors intensely.  A small amount of oxide affords a glass which, while warm, is violet, and becomes of a pale reddish-brown on cooling.  A larger addition produces a dark violet color in the warm and reddish-brown in the cold bead.

    in the reducing flame.

The oxide is reduced and the metallic particles give the bead a turbid grey appearance.  If the blast be continued the metallic particles fall together without fusing, and the glass becomes colorless.  This reaction is readily obtained with tin upon charcoal, and the reduced nickel fuses to a bead with the tin.

  Behavior with Mic.  Salt on Platinum wire

    in the oxidizing flame.

      Dissolves into a reddish glass which becomes yellow on cooling. 
      With a large addition of the oxide, the glass is brownish while
      hot, and orange when cold.

    in the reducing flame.

On platinum wire the nickeliferous bead undergoes no change.  Treated with tin upon charcoal, it becomes at first opaque and grey, and after long continued blowing the reduced nickel forms a bead, and the glass remains colorless.

* * * * *

8.  Oxide of Zinc, ZnO.

  Behavior with Borax on Platinum wire

    in the oxidizing flame.

Dissolves easily into a clear colorless glass, which, when much oxide is present, may be rendered opaque and flocculent by an intermittent flame, and becomes so spontaneously with a still larger addition.  When a considerable quantity is dissolved, a glass is obtained which is pale yellow, while hot, and colorless when cold.

    in the reducing flame.

On platinum wire the saturated glass becomes at first opaque and grey, but by a sustained blast is again rendered clear.  On charcoal the oxide is gradually reduced; the metal is volatilized and in crusts the charcoal with oxide.

  Behavior with Mic.  Salt on Platinum wire

    in the oxidizing flame.

      As with borax.

    in the reducing flame.

      As with borax.

* * * * *

9.  Oxide of Cadmium, CdO.

  Behavior with Borax on Platinum wire

    in the oxidizing flame.

When in very large proportion, dissolves to a clear yellow glass, which becomes nearly colorless on cooling.  When the oxide is present in any considerable quantity, the glass can be rendered opaque with an intermittent flame, and, with a larger addition, it becomes so spontaneously on cooling.

    in the reducing flame.

      Upon charcoal ebullition takes place and the oxide is reduced. 
      The metallic cadmium is volatilized and incrusts the charcoal
      with its characteristic deep yellow oxide.