ween hammer and plate.

To coat with mercury only, procure some nitrate of mercury. This is
easily made by placing mercury in an earthenware bowl, pouring somewhat
dilute nitric acid on it, and letting it stand till the metallic mercury
is changed to a white crystal. Dense reddish-brown fumes will arise,
which are injurious if breathed, so the operation should be conducted
either in the open air, or where there is a draught.

Having your silvering solution ready, which is to be somewhat diluted
with water, next take two swabs, with handles about 12 inches long, dip
the first into a basin containing dilute nitric acid, and rub it rapidly
over about a foot of the surface of the plate; the oxide of copper will
be absolutely removed, and the surface of the copper rendered pure and
bright; then take the other swab, wet with the dilute nitric of mercury,
and pass it over the clean surface, rubbing it well in. Continue this
till the whole plate has a coating of mercury. It may be well to go
over it more than once. Now turn on the water and wash the plate clean,
sprinkle with metallic mercury, rubbing it upwards until the plate will
hold no more.

A basin with nitrate of mercury may be kept handy, and the plates
touched up from time to time for a few days until they get amalgamated
with gold, after which, unless you have much base metal to contend with,
they will give no further trouble.

It must be remembered, however, that an excessive use of nitric acid
will result in waste of mercury, which will be carried off in a milky
stream with the water; and also that it will cause the amalgam to become
very hard, and less active in attracting other particles of gold.

If you are treating the plate with nitrate of silver prepared as already
mentioned, clean the plate with dilute nitric acid, rub the surface with
the ball of amalgam, following with the swab and fairly rubbing in. It
will be well to prepare the plate some days before requiring to use
it, as a better adhesion of the silver and copper takes place than if
mercury is applied at once.

To amalgamate with zinc amalgam, clean the copper plate by means of a
swab, with fairly strong sulphuric acid diluted with water; then while
wet apply the zinc-mercury mixture and well rub in. To prepare the
zinc-amalgam, clip some zinc (the lining of packing cases will do)
into small pieces and immerse them in mercury after washing them with
a little weak sulphuric acid and water to rem