ch is
familiar to everybody, is obtained by this process.

(2) Finely turned and finished Brass Work. If it is intended to
nickel-plate such work, and if it is desirable to obtain brightly
polished nickel surfaces, the work must be perfectly polished to begin
with. Full details as to polishing may be found in workshop books or
treatises on watch-making. It will suffice here to say that the brass
work is first smoothed by the application of successive grades of
emery and oil, or by very fine "dead" smooth files covered with chalk.
Polishing is carried out by means of rotten stone and oil applied on
leather.

In polishing turned work care must be taken to move the file, emery,
or rotten stone to and fro over the work with great regularity, or the
surface will end by looking scratchy and irregular. The first process
of cleaning is, of course, to remove grease, and this is accomplished
best by dipping in a bath of strong hot caustic soda solution, and
less perfectly by heating the work and dipping it in the cold caustic
soda bath.

During this process a certain amount of chemical action often occurs
leading to the brass surface exhibiting some discoloration. The best
way of remedying this is to dip the brass into a hot bath of cyanide
of potassium solution. If it is inconvenient to employ hot baths or
to heat the brass work, good results may be obtained by rubbing the
articles over with a large rough cork plentifully lubricated with a
strong solution of an alkali.

If the surfaces are very soiled or dirty, a paste of alkali and fine
slaked lime may be applied on a cork rubber, and this in my experience
has always been most effective and satisfactory in every way, except
that it is difficult to get into crevices. If the alkali stains the
work, a little cyanide of potassium may be rubbed over the surface in
a similar manner.

Brass work treated by either of these methods is to be washed in clean
water till the alkali is entirely removed, and may then be
nickel-plated without any preliminary scratch-brushing. The treatment
in hot baths of alkali and cyanide is the method generally employed in
American factories as a preliminary to the nickelling of small brass
work for sewing machines, etc.

(3) Copper either for use as the kathode in electrolysis calibration
experiments or otherwise is most conveniently prepared by dipping in
the acid bath, rinsing quickly in cold water, scratch-brushing under
cold water, and