Other formulae are as follows:
Double nickel-ammonium sulphate, 4 parts.
Ammonium carbonate, 3 "
Water 100 "
Nickel sulphate, nitrate or chloride, 1 "
Sodium bisulphate, 1 "
Water, 20 "
Nickel anodes are used in the bath to maintain the strength. Too much
care cannot be exercised in the absolute cleanliness of the articles to
be plated. A too alkaline bath gives a disagreeable yellow color to the
deposit; too acid a bath gives badly adhering deposits.
Night Bell.
An alarm bell in a telegraph office, which bell is connected at night to
give a loud signal to attract the operator's attention. It is used in
telephone exchanges and is connected so as to ring as long as a
subscriber remains unanswered after calling.
Nobili's Rings.
When a dilute solution of copper acetate is placed on a bright silver
plate and a strip of zinc is touched to the silver beneath the copper, a
series of rings of copper are formed by electrolysis around the zinc.
These are Nobili's rings.
If for the copper acetate a solution of lead oxide in potassium hydrate
solution is substituted, and if the polished plate which may be German
silver is connected to the positive electrode of a battery, and a
platinum wire connected to the negative pole is immersed in the liquid,
it determines the formation of beautiful iridescent rings of lead
binoxide. The platinum wire is sometimes sealed in glass so that only
its point projects.
The colors are due to interference of light, the layers of lead oxide
being extremely thin.
The lead binoxide is formed by secondary reaction. Metallic lead is
first deposited on the negative pole. The oxygen which goes to the
positive pole formed by the polished plate produces lead binoxide which
is deposited there in rings. The reaction is comparable to that of a
storage battery.
Synonyms--Metallochromes--Electric Rings.
Nodular Deposit.
A deposit obtained in electroplating, characterized by irregular
thickness; due to too low density of current.
Non-conductor.
A material that does not conduct electricity except with great
difficulty; a substance of very high resistance.
Synonym--Insulator--Dielectric.
North Pole.
(a) The north-seeking pole of a magnet; the pole of a magnet which tends
to point to the north, and whence lines of force are assumed to issue on
their course to the other pole of the magnet.
(b) The North Pole of the earth. Treating the earth as a magnet, and
accepting the above nomenclature the north pole should be termed the
south pole. (See Austral Pole--Boreal Pole.)