Pour; when cold,
detach the button of speise, and weigh.
Weigh out carefully a portion of about 1 gram of it. Place a shallow
clay dish in the muffle, and heat it to bright redness; then add about
1.5 gram of borax glass wrapped in a piece of tissue paper; when this
has fused, drop the piece of speise into it. Close the muffle until the
speise has melted, which should be almost at once. The arsenide of iron
will oxidise first, and when this has ceased the surface of the button
brightens. Remove it from the muffle, and quench in water as soon as the
button has solidified. The borax should be coloured slightly blue.
Weigh: the loss is the arsenide of iron. Repeat the operation with the
weighed button on another dish, using rather less borax. Continue the
scorification until a film, green when cold, floating on the surface of
the button shows that the nickel is beginning to oxidise. Cool,
separate, and weigh the button as before. The loss is the arsenide of
cobalt.
If copper is absent, the speise is now arsenide of nickel.
The weight of nickel corresponding to the arsenide got is calculated by
multiplying by 0.607; and, similarly, the weight of the cobalt is
ascertained by multiplying the loss in the last scorification by
0.615.[71] It must be remembered that the nickel and cobalt so obtained
are derived from a fraction only of the speise yielded by the ore taken,
so that the results must be multiplied by the weight of the whole of the
speise, and divided by the weight of the fragment used in the
determination.
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