GIL 



GIM 



verdigris moistened with water, will an- 

 swer the purpose. 



Copper, and the alloys formed by its 

 combination with zinc, are gilded nearly 

 in the same manner as silver; but as their 

 affinity for mercury is coniderably less 

 that that of silver, it would be difficult to 

 made the amalgam of gold adhere to the 

 burnished surface of these metals by the 

 same means, and with the same evenness, 

 as takes place in the case last described. 

 To obviate this inconvenience, advantage 

 is very ingeniously taken of the action of 

 nitric acid to facilitate the adhesion of 

 the copper and mercury, in the following 

 manner. A piece of copper, a button for 

 example, is cleaned, by steeping it in 

 acid, and subsequent washing, and is then 

 burnish ed, either in a lathe, or by any 

 other means : after this it is dipped in a 

 neutralized solution of nitrate of mercury, 

 and in the space of a few minutes, owing 

 to the strong 1 affinity of nitric acid for 

 copper, the mercurial salt is decomposed, 

 the copper takes the place of the mercu- 

 ry, and at the same time the mercury is 

 deposited in the metallic state on the 

 surface of the copper, covering it entire- 

 ly, and strongly adhering to it ; the gold 

 amalgam is now applied, and the rest of 

 the process goes on as already described. 

 By this method of proceeding, a given 

 quantity of gold may be made to cover a 

 larger surface than in any other way of 

 gilding on metals; five grains of gold will 

 completely gild both the upper and un- 

 der surfaces of one hundred and forty- 

 four copper buttons, each of them an inch 

 in diameter. 



There is no metal, the gilding of which 

 presents so many difficulties as iron, or 

 rather steel. If the method of simple 

 burnishing down is had recourse to, the 

 heat requisite for this purpose will, in ma- 

 ny cases, bring the temper of the steel 

 too low : on such occasions, the way al- 

 ready described for gilding on copper is 

 sometimes practised ; that is, the parts 

 of the steel to be gilded are pencilled 

 over with nitrate of mercury, by which 

 they are covered with a slightly adhering 

 coat of mercury ; then the amalgam is ap- 

 plied, and the gilding finished in the usual 

 way. The objections to this mode of pro- 

 ceeding are, first, that a considerable heat 

 is required, though inferior to that requi- 

 site for burnishing down ; and, secondly, 

 that, even with all possible care, the gild- 

 ing is apt to be rough and scale off. A 

 very considerable improvement in this 

 way of gilding is, to trace the figure of 

 the gilding on the steel first of all, with a 



brush charged with a strong solution of 

 sulphated copper, in consequence of 

 which a pretty thick plate of this metal is 

 deposited on the steel, to which it may 

 be made to adhere, with considerable 

 firmness, by means of the burnisher ; thus 

 the gilding is, in fact, performed upon 

 the copper. 



A new method of gold-gilding upon, 

 steel has lately been published, possessed 

 of many advantages over the others, and 

 probably in time may attain to a very high 

 degree of perfection. It depends upon 

 the well known fact, that, if sulphuric 

 ether and nitro-muriate of gold are mix- 

 ed together, the ether will, by degrees, 

 separate from the acid nearly the whole 

 of the gold, and retain it for some time in 

 solution, in nearly a metallic state. If 

 ether, thus charged with gold, is spread, 

 by means of a pen or fine brush, on the 

 surface of highly polished steel, the ether 

 presently evaporates, leaving the gold be- 

 hind in close contact with the steel, and 

 the adhesion is considerably improved by 

 the subsequent application of the bur- 

 nisher. The dearness, and especially the 

 rapid volatility of ether, are, at first, ob- 

 jections of some moment, but may be got 

 over by using the best oil of turpentine 

 instead of ether, which, has nearly the 

 same efficacy in decomposing the nitro- 

 muriate of gold, and is both cheaper, and 

 not so very quickly evaporable. 



Gold-gilding upon silver is, we believe, 

 at present entirely disused. It was per- 

 formed in the following manner : a satu- 

 rated solution of gold, in nitro-muriatic 

 acid, was poured upon some linen rags, 

 and, when they were become dry, they 

 were heaped in a plate, and touched with 

 a hot coal. The fire gradually spread 

 through the mass, and reduced it to a 

 heavy black ash. A soft cork, being 

 moistened in water, was dipped in this ash, 

 to which a part of it adhered, and was 

 then rubbed on the surface of polished 

 silver, upon which the minute particles 

 of gold became fixed, and covered it with 

 an extremely thin coating, which, when 

 burnished, exhibited the genuine colour 

 and lustre of the precious metal. JUkirfs 

 Diet. 



GILL, a measure of capacity, contain- 

 ing a quarter of a pint. 



GILT varnish. See VARNISH. 



GIMBALS, in sea affairs, the brass 

 rings by which a sea compass is suspend- 

 ed in its box, so as to counteract the ef- 

 fect of the ship's motion, and keep the 

 card horizontal. 



