lved to a strong blue solution. The cyanide and
bisulphite solution is then added with warming till the blue colour is
destroyed. This usually requires the exact amount of cyanide and
bisulphite mentioned, but I have not found it essential to entirely
destroy the colour.

The solution contains cuprocyanide of sodium and ammonium (?), which
is not very soluble, and this salt tends to be deposited in granular
crystalline masses on standing. However, at a temperature of 50 deg. C.
the above receipt gives an excellent coppering liquid, which will coat
zinc with a fine reguline deposit. Brass or copper partly smeared
with solder will receive a deposit of copper on the latter as well as
on the former, and, moreover, a deposit which appears to be perfectly
uniform.

In using the bath the anode tends, as a rule, to become incrusted, and
this rapidly increases the resistance of the cell, so that the current
falls off quickly. The articles should be scratch-brushed and plated
for about two minutes with a current density of about ten amperes per
square foot.

As soon as the deposit begins to look red the articles are to be
removed and rebrushed, after which the process may be continued.
About five minutes' plating will give a copper deposit quite thick
enough after scratch-brushing to allow of a very even gilding or
silvering.

Aluminium appears to be fairly coated, but, as usual, the copper
strips after soldering. Iron receives an excellent and adherent coat.

I do not think that the formation of a crust upon the anode can be
entirely prevented. According to Gore, its formation is due to the
solution being too poor in copper, but I have added a solution of the
acetate of copper and ammonium till the colour was bright blue without
in any way reducing the incrustation. If the solutions become
violently blue it is perhaps as well to add a little more cyanide and
bisulphite, but I have not found such an addition necessary. The
process is one of the easiest and most satisfactory in
electro-metallurgy.

Sec. 141. Nickel-plating.

An examination of several American samples of nickel-plated goods has
disclosed that the coating of nickel is, as a rule, exceedingly thin.
This is what one would expect from laboratory repetition of the
processes employed.

Commercial practice in the matter of the composition of nickelling
solutions appears to vary a good deal. Thin coatings of nickel may be
readily given in a solution