of the double sulphate of nickel and
ammonia, which does rather better if slightly alkaline. Deposits from
this solution, however, become gray if of any thickness, and,
moreover, are-apt to flake off the work. The following solution has
given very good results with me. It is mentioned, together with
others, in the Electrical Review, 7th June 1895.

The ingredients are:-

Nickel sulphate 5 parts

Ammonia sufficient to neutralise the nickel salt.

Ammonium tartrate 3.75 parts

Tannin 0.025 parts

Water 100 parts

The nickel sulphate and ammonia are dissolved in half the water, the
ammonium tartrate in the other half with the tannin. The solutions
are mixed and filtered at about 40 deg. C. This solution works well at
ordinary temperatures, or slightly warm, with a current density of ten
amperes per square foot. In an experiment made for the purpose I
found that plating may go on for an hour in this solution before the
deposit begins to show signs of flaking off. The deposit is of a fine
white colour.

The resistance of the bath is rather high and rather variable,
consequently it is as well to have a current indicator in circuit, and
it may well happen that five or six volts will be found requisite to
get the current up to the value stated. For nickelling small objects
of brass, such as binding screws, etc, it is very necessary to be
careful as to the state of polish and uniformity of their surfaces
before placing them in the plating bath. A polished surface will
appear when coated as a polished surface, and a mat surface as a mat
surface; moreover, any local irregularity, such as a speck of a
foreign metal, will give rise to an ugly spot in the nickelling bath.
For this reason it is often advisable to commence with a coat of
copper laid on in an alkaline solution and scratch-brushed to absolute
uniformity.

An examination of the work will, however, disclose whether such a
course is desirable or not; it is not done in American practice, at
all events for small brass objects. These are cleaned in alkali and
in boiling cyanide, which does not render a polished surface mat, as
weak acid is apt to do, and are then coated with a current density of
about ten amperes per square foot.

In spite of what is to be found in books as to the ease with which
nickel deposits may be polished, I find that the mat surface obtained
by plating on an imperfectly polish