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ARTIFICIAL dentures: ELECTRO-DEPOSIT. I05
It slunilcl now 1)e set aside to cool, when, after a few hours,
crystals of silver nitrate will have deposited, from which
the remaining- li(|uid is to he poured of¥. Another method
is to evaporate to dryness, hy which the free acid is all
driven off.
Preparation of Silver Cyanid Solution.—Dissolve the
prepared crystals of silver nitrate in three pints of distilled
water, which should be effected in a glass dish, glazed
earthenware, or stoneware vessel. Add to this solution a
small qurmtity of common salt, a little at a time, until pre-
cipitation of silver chlorid ceases. Now pour off the clear
solution and wash the chlorid of silver several times with
distilled water.
A strong solution of potassium cyanid (about Vj a pound
to I quart of water is usually employed) is now added to
this white precipitate, a little at a time, when the silver
cyanid will be formed. While the solution is being added
it should be well stirred with a glass rod. In making up a
cjuart of the solution, use the i ounce of fine silver, pre-
viously alluded to, with one-cjuarter of a pound of potassium
cyanid, and a quart of distilled water.
Silver Bronze for Plaster Cast.—In preparing silver
bronze for the cast, place a small cjuantity of silver chlorid
in a dish and add a few drops of sulphuric acid and a small
piece of zinc. After all action has ceased, the silver bronze
thus formed is thoroughly washed and dried.
Preparation of Plaster Cast.—A piece of copper wire is
placed around the cast and the ends twisted until it is thor-
oughly secured. The cast is then immersed in melted wax,
after which it is carefully and thoroughly coated w^ith the
silver bronze, which is best applied with the end of the
finger.
Manner of Making Attachment to the Battery.—In this
work Nos. I, 2, or 3 Bunsen battery may be employed. To