Scientific American Supplement, No. 586, March 26, 1887Various
Science
Scientific American Supplement, No. 586, March 26, 1887
Various
Science -- Periodicals
When an article has been nickel plated, it generally presents a dull
appearance, resembling frosted silver. To get over this I tried, some time
ago, the use of bisulphide of carbon in the same way as used for obtaining
a bright silver deposit. Curiously the deposit was very dark, almost black,
which could not be buffed or polished bright. But by using a very small
quantity of the bisulphide mixture, the plated surfaces were so bright that
the use of polishing mops or buffs could be almost dispensed with. When we
consider the amount of labor required in polishing a nickel plated article,
and the impossibility of finishing off bright an undercut surface, this
becomes an important addendum to the nickel plater's list of odds and ends.
This mixture is made precisely in the same way as for bright silvering, but
a great deal less is to be added to the bath, about one pint per 100
gallons. It should be well stirred in, after the day's work is done, when
the bath will be in proper condition for working next day. The mixture is
made by shaking together, in a glass bottle, one ounce bisulphide and one
gallon of the plating liquid, allow to stand until excess of bisulphide has
settled, and decant the clear liquid for use as required. It is better to
add this by degrees than to run the risk of overdoing. If too much is
added, the bath is not of necessity spoiled, but it takes a great deal of
working to bring it in order again.
About eight ounces of the double sulphate to each gallon of distilled or
rain water is a good proportion to use when making up a bath. There is a
slight excess with this. It is a mistake to add the salt afterward, when
the bath is in good condition. The chloride and cyanide are said to give
good results. I can only say that the use of either of these salts has not
led to promising results in my hands.
In preparing the double sulphate, English grain nickel is decidedly the
best form of metal to use. In practice, old anodes are generally used.
The metal is dissolved in a mixture of nitric and dilute sulphuric acid,
with the application of a gentle heat. When sufficient metal has been
dissolved, and the unused nitric acid expelled, the salt may be
precipitated by a strong solution sulphate of ammonia, or, if much free
acid is present, carbonate of ammonia is better to use.
Tin, lead, and portion of the iron, if present, are removed by this method.
The silica, carbon, and portions of copper are left behind with the
undissolved fragments of metals.
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