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MISCELLANEOUS ELECTRICAL APPARATUS 369

The electrolyte is composed of one part of nickel—sul-
phate dissolved in twenty parts of water to which one part
of sodium-bisulphate is added.

This mixture is placed in the tank instead of the copper-
sulphate. The objects to be plated are hung from the
copper rod connected to the negative pole of the battery.

When the nickel-plated articles are removed from the
bath they will have a dull, white color known as “ white
nickel.” When white nickel is polished with a cloth wheel
revolving at high speed, and known as a buffing-wheel, it
will assume a high luster.

HOW TO MAKE A RHEOSTAT

It is often desirable to regulate the amount of current
passing through a small lamp, motor, or other electrical
device operated by a battery.

This is accomplished by inserting resistance into the
circuit. A rheostat is an arrangement for quickly altering
the amount of resistance at will.

A simple rheostat is easily made by fitting a five-point
switch such as that shown in Figure 95 with several coils
of German-silver resistance wire. German silver has much
more resistance than copper wire, and is used, therefore,
because less will be required, and it will occupy a smaller
space.

A five-point switch will serve satisfactorily in making a
rheostat, but if a finer graduation of the resistance is de-
sired it will be necessary to use one having more points.

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