5€6 
gilding. 
nated “by artiits mercurial water. The acid, which has tL 
greater affinity for tlie iron than for the mercury, at¬ 
tacks the former, and depofits a thin layer of mercury 
inftead of that of iron, which it takes away. This layer 
efledfs the union ot the amalgam which is then applied 
with the iron ; which combination would not have taken 
place without it. But by this procefs the furface of the 
iron is injured by the aiflion of the nitric acid, and the 
union is fo flight tliat a brilliant and durable gilding 
can never be produced by this method. 
Gilding with the Amalgam and the Sulphat of Copper.—~ 
Sometimes with a camel-hair pencil a folution of Ailphat 
of copper is applied to that part of the fteel which is 
propoied to be gilded. By a chemical affinity, exabfly. 
fimilar to that juft deferibed, a thin layer of copper is 
precipitated upon the iron. The copper having an affi¬ 
nity for the mercury, is capable of ferving as an interme¬ 
diate fubftance, and eftetling a kind of union between 
the amalgam and the iron. But in both of thefe pro- 
celFes the furface of the fteel is always injured by the 
adtion of the acid, and in both a degree of heat muft 
likewife be employed fufficient to volatilize the mer¬ 
cury. In confequence of thefe difadvantages moft artifts 
adopt the ifirft procefs, which confifts in applying the 
gold-leaf to the metal when hot, and in fixing it by the 
addion of the burnilher. This procefs is troublefome, 
but the furface of the iron is lefs liable to be injured 
by it. 
Improved Procefs for gilding Iron or Steel .—This procefs 
is as yet but little known. Into a folution of gold in 
nitro-muriatic acid pour about twice the quantity of 
ether ; this mixture ftiould be made with care, and in 
a large velfel. Shake the two liquids together, and as 
I'oon as the mixture has fettled, the ether will be feen 
feparating from the nitro-muriatic acid, and floating on 
the furface. The acid becomes colourlefs, and the ether 
acquires a colour, becaufe it takes away the gold from 
the acid. The two liquids are poured into a glafs fun¬ 
nel, the pipe of which muft be very fmall, and muft be 
flopped till the tw'o fluids have fettled, when they will 
be completely feparated from each other. Being then 
opened, the acid which, on account of its w'eight, is 
lowernioft, runs out the firft ; when it is entirely drawn 
oft, ftop the funnel, which then contains only the folu¬ 
tion of gold in etiier; this is put into a phial, well 
corked, and kept for ufe. To gild iron or fteel with 
this preparation, firft pblifti the furface with the fineft 
emery, or rather with colcothar moiftened with brandy, 
'fhen, with a fmall brufti or pencil, apply the auriferous 
ether; the liquid loon evaporates, and the gold remains. 
Heat, and afterwards rub it with the burnilher. By means 
ot this lolution of gold in ether, the artift may, with a 
pen or pencil, trace all kinds of figures upon iron, which 
is the method employed for plating the wares of Soh- 
lingen. As every artift may not have at hand the re¬ 
ceipts for the beft method of preparing nitro-muriatic 
acid and ether, w'e lhall here fubjoin them. 
For the Solution of Gold in Nitro-muriatic Acid .—Into a 
fufficient quantity of nitrous acid put as much lal-am- 
luoniac as it is capable of diflblving cold, and even in a 
cool place. Into this acid put gold reduced to filings 
or thin leaves, and place it in a fituation where it will 
become warm till the metal is completely diffolved. 
1 he folution aft'umes a yellow colour, being that of the 
gold, and ftains the Ikins of animals purple. 
Method of preparing Sulphuric Ether .—Into a large retort 
put one pound and a half of highly-reftified I'pirit of 
wine, to which pour flowly two pounds of the moft con. 
centrated fulphuric acid, llightly agitating the mixture 
as you add the acid. The mixture will become warm, 
and the vapours that will be abundantly difengaged will 
have a pirngent fmell. When you have poured in all 
Ibiie fulphuric acid, add half a pound of Ipirit (tf wine, 
which will rince the neck of the retort on its palfage ; 
mix the whole well, and .let it ftand for fome time, pre- 
vioufly clofing the mouth of the retort. jPlace it after¬ 
wards on a fand-bath ; adapt to it a large recipient, and 
kindle the fire : it ftiould be flow and moderate, and the 
heat ought not to be communicated to the recipient. 
Continue the operation till a fulphuric fmell is emitted" 
from the globe of the recipient. Unlute and collect the 
produce, which is a mixture of ether, acidulated water,, 
fpirit of wine, fulphuric acid, and a carbonic matter. 
To reilify this, put it again into a retort; and after 
adding a fmall quantity of alkali to abforb the acid, 
place the retort on the fand-batli, which heat very mo¬ 
derately ; the firft half of the liquid that palfes over is 
extremely pure ether. The refidue of the firft diftilla- 
tion may be employed to prepare a farther quantity of 
ether. It will be fufficient to pour upon it fome good 
fpirit of wine, but lefs in quantity by one-third than 
the firft time ; diftil, rectify, &c. Thofe w'ho may find 
a difficulty in preparing ether may fubftitute for that 
liquid an eftential oil, as fpirit of lavender, oil of tur¬ 
pentine, &c. thefe liquids poft'efs the property of fepa^- 
rating gold from a nitro-muriatic folution. 
Of gilding Silver cold .—Independently of the preceding 
methods, lilvermay be gilded cold, and with great eafe, 
by means of the following procefs. Dilfolve fome gold 
in nitro-muriatic acid, and dip linen rags in the folution. 
Burn the rags, carefully preferving the a,fhes, which 
will be very black, and, by retaining the gold are found 
much heavier than common afnes. Rub them on the 
furface of the filver you intend to gild, for which pur- 
pofe a piece of leather or cork may be employed. 
This aftion attaches the particles of gold to the furface 
of the filver ; wafh the latter, when you will perceive 
fome flight traces of gilding; which will appear much 
more diftinflly when rubbed with the burniflter. This 
procefs ij ufually called dry-gilding. 
Of gilding Brafs .—The furface of delicate inftruments 
made of brafs may be preferved a confiderable time tin- 
injured, by gilding them in the following manner. Pro¬ 
cure a folution of faturated gold, and after having eva¬ 
porated it to the confiftence of oil, leave it to cryftal- 
lize. Diflblve the cryftals in pure water, and after 
plunging into this folution the articles that are to be 
gilded, wafh them in pure water, and fubmit them to 
tlie adtion of the burnilher. Repeat the procefs till they 
are completely gilded. The folution of the cryftals of 
nilro-muriat of gold is preferable to a fimple folution 
of the metal, becaufe the latter always contains a portion 
of acid at liberty, which attacks more or lefs powerfully 
the furface of the brafs, and deftroys its polifli. 
Method of Gold-varnifnng Brafs .—A varnifh, very much 
refembling the gold varnifti of Palermo deferibed above, 
may be applied to brafs, by covering it with a folution 
of gum-lac in fpirit of wine. It preferves its brilliancy 
as long as the varnifh lafts. The articles prepared in 
this way muft not be rubbed with too hard a brufti, or 
with, chalk ; they muft only be wetted with linen raga. 
This varnifti is prepared in the following manner. Dif- 
folve two ounces of very pure gum-lac in forty-eight 
ounces of alkohol, and place the folution upon a fand- 
bath in a moderate heat. To prevent part of the fpirit 
of wine from evaporating, as well as the veffel from 
burfting if too clofely flopped, cover the neck with a 
bladder, in which leveral holes muft be made with a 
pin. In another veffel, and in the fame quantity of 
fpirit of wine, diffolve an ounce of gum-tragacanth, in 
grains. Mix the two folutions when complete ; put 
into it three grains of fanders Wood, and let the wiiole 
ftand for twelve hours in a moderate heat. Filtre 
through paper, and keep it for ufe in a very clean phial. 
Sanders wood is preferable to any other fubftance for 
giving a gold colour to the varnifh made with lac. If 
you intend it to be pale, and not to alter the colour of 
the brafs, omit this cplouring principle ; and if you 
want a higher gold yellow, add half as much more 
wood as tlie quanlity Ipecified above. 
