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vitrifying； cements the gold with great firmness to the glass； after which
it may be burnished。
The gilding upon porcelain is in like manner fixed by heat and the use of
borax； and this kind of ware； being neither transparent nor liable to
soften； and thus to be injured in its form in a low red heat； is free from
the risk and injury which the finer and more fusible kinds of glass are
apt to sustain from such treatment。 Porcelain and other wares may be
platinized； silvered； tinned； or bronzed； in a similar manner。
16。 GILDING THE EDGES OF PAPER
The edges of the leaves of books and letter paper are gilded whilst in a
horizontal position in the bookbinder's press or some arrangement of the
same nature； by first applying a composition formed of four parts of
Armenian…bole and one of candied sugar； ground together with water to a
proper consistence； and laid on by a brush with the white of an egg。 This
coating； when nearly dry is smoothed be the burnisher； it is then slightly
moistened by a sponge dipped in clean water and squeezed in the hand； the
gold leaf is now taken up on a piece of cotton from the leathern cushion
and applied on the moistened surface； when dry it is to be burnished by
rubbing the burnisher over it repeatedly from end to end； taking care not
to wound the surface by the point。
17。 PROFESSOR WORTS' AMALGAM FOR SILVERING
This is the only means yet discovered for silvering iron directly； yet it
is not so lasting as some of the other processes。 Take quicksilver and the
metal potassium； equal parts by volume； put them together in a tumbler；
and if both metals be good there will be a brisk ebullition； which
continues until an amalgam of the two is formed； then add as much
quicksilver as there is of the amalgam； let it work till thoroughly mixed；
and it is ready for use。 This amalgam you may apply with a cloth to any
metal； even iron； though it be a rusty bar； and you have it neatly
silvered over。
18。 FOR COPPERING IRON
This is the latest method； and that now in use。 To a solution of sulphate
of copper； add a solution of ferrocyanide of pottasium； so long as a
precipitate continues to be formed。 This is allowed to settle； and the
clear liquor being decanted the vessel is filled with water； and when the
precipitate settles the liquor is again decanted； and continue to repeat
these washings until the sulphate of potash is washed quite out； this is
known by adding a little chloride of barium to a small quantity of the
washings； and when there is no white precipitate formed by the test； the
precipitate is sufficiently washed。 A solution of cyanide of potassium is
now added to this precipitate until it is dissolved； during which process
the solution becomes warm by the chemical re…action which takes place。 The
solution is filtered； and allowed to repose all night。 If the solution of
cyanide of potassium that is used is strong； the greater portion of the
ferrocyanide of potassium crystalises in the solution； and may be
collected and preserved for use again。 If the solution of cyanide of
potassium used to dissolve the precipitate is dilute； it will be necessary
to condense the liquor by evaporation to obtain the yellow prussiate in
crystals。 The remaining solution is the coppering solution； should it not
be convenient to separate the yellow prussiate by crystallization； the
presence of that salt in the solution does not deteriorate it nor
interfere with its power of depositing copper。
19。 PECULIARITIES IN WORKING CYANIDE OF COPPER SOLUTION
The true composition of the salts thus formed by copper and cyanide of
potassium has not yet been determined； but their relations to the battery
and electrolyzation are peculiar。 The solution must be worked at a heat
not less than from 150~ to 200~ Farenheit （that is not quite as hot a
boiling water； which is 212~ Farenheit。） All other solutions we have tried
follow the laws； that if the electricity is so strong as to cause gas to
be evolved at the electrode； the metal will be deposited in a sandy or
powdered state； but the solution of cyanide of copper and potassium is an
exception to these laws； as there is no reguline deposit obtained unless
gas is freely evolved from the surface of the article upon which the
deposit is taking place。 As this solution is used hot； a considerable
evaporation takes place； which requires that additions be made to the
solution from time to time。 If water alone be used for this purpose it
will precipitate a great quantity of the copper as a white powder； but
this is prevented by dissolving a little cyanide of potassium in the water
at the rate of 4 ounces to the gallon。 The vessels used in factories for
this solution are generally of copper； which are heated over a flue or in
a sand…bath； the vessel itself serving as the positive electrode of the
battery； but any vessel will suit if a copper electrode is employed when
the vessel is not of copper。
20。 PREPARATION OF IRON FOR COATING WITH COPPER
When it is required to cover an iron article with copper； it is first
steeped in hot caustic potash or soda to remove any grease or oil。 Being
washed from that it is placed for a short time in diluted sulphuric acid；
consisting of about one part acid to 16 parts of water； which removes any
oxide that may exist。 It is then washed in water and scoured with sand
till the surface is perfectly clean； and finally attached to the battery
and immersed in the cyanide solution。 All this must be done with despatch
so as to prevent the iron combining with oxygen。 An immersion of five
minutes duration in the cyanide solution is sufficient to deposit upon the
iron a film of copper； but it is necessary to the complete protection of
the iron that it should have a considerably thick coating； and as the
cyanide process is expensive； it is preferable when the iron has received
a film of copper by the cyanide solution； to take it out； wash it in
water； and attach to it a simple cell or weak battery； and put it into a
solution of sulphate of copper。 If there is any part not sufficiently
covered with copper by the cyanide solution； the sulphate will make these
parts of a dark colour； which a touch of the finger will remove。 When such
is the case； the article must be taken out； scoured； and put again into
the cyanide solution till perfectly covered。 A little practice will render
this very easy。 The sulphate solution for covering iron should be prepared
by adding it by degrees a little caustic potash； so long as the
precipitate formed is re…dissolved。 This neutralizes a great portion of
the sulphuric acid； and thus the iron is not so readily acted upon。 When
the iron is thus coppered； proceed to silver it in the manner recommended
for silvering according to receipt No。9； or if you want to put a very
heavy coating of silver on it； make use of a strong battery。
21。 SOLDERING FLUID
For mending articles of tin； iron； zinc； copper； and almost all other
metals。 Take 2 fl。 ou