GOLD. 



in the year 1717, that in the mints of Spain and Pof tugal the 

 value of gold is fixteen times that of filver ; but that in thofe 

 countries, payments in filver bearing generally a premium of 

 fix per cent, the proportion may be confidered as fixed by 

 commerce at 15 .V to I ; that in the other parts of Europe, 

 the value of gold is at moit fifteen, and in China and Japan 

 but nine or ten times that of filver ; fo that gold is rated 

 higher in England than in any other part of Europe, and 

 higher in Europe than in the Eaftern countries. Hence, in 

 great meafure, arife the profits of exchanging gold for filver 

 in one place, and re -exchanging them in another ; and hence 

 the o-reater difparity between the relative quantities of gold 

 and filver in one commercial nation than in another ; this me- 

 tal being brought in moll abundance which is rated highefl 

 in proportion to the other, and that which is rated loweil be- 

 ing drained away. There are various ways of determining 

 the finenefs of gold ; or the proportion of alloy which it 

 contains. Thole who are nfcd to this bufinefs can judge 

 nearly the proportion of alloy from the colour of any given 

 mafs, provided that the fpecies of alloy be known. For the 

 method of doing this, fee Tovcil-needks. The great excefs 

 of the weight of gold, above that of the metals ufed for its 

 alloy, affords another method of determining the quantity of 

 alloy in any given mafs, where the fpecies of alloy is known. 

 Thus fine gold lofes in water one grain in every 19.3 nearly ; 

 and fine filver lofes one grain in about eleven ; from whence 

 it is eafy to find the lofs of any number of grains of each, 

 and confcquenlly of any affignable mixture of the two me- 

 tals. Thus, fifty grains of gold will lofe above 2/, and fifty 

 grains of filver fomewhat more than 4' ; fo that a mixture 

 of equal parts of the two will lofe above feven in a hun- 

 dred, or one in fo\irteen. A mixture of gold with half its 

 weight of filver will lofe one part in 1 5.4 ; with a third of 

 filver, one in 16.2 ; with a fourth, one in 1.67 ; and with an 

 eleventh of filver,' which is the llnndard proportion of alloy, 

 one in 18 I. On this principle, the fpecific gravity or pro- 

 portional lofs in water, of gold alloyed with different quan- 

 tities of filver, copper, and mixtures of both, may be com- 

 puted and formed into tables for ufe. The accuracy of this 

 method, it fhould be obferved, depends on the fuppofition 

 that each of the two metals, that are melted together, re- 

 tains its own proper gravity, which is the cafe in mixtures 

 of gold and filver ; but gold and copper, melted together, 

 are fpecifically lighter than if thev were weighed feparatelv ; 

 or the fpecific gravity of tiie alloy is lefs than that of the 

 mean of its ingredients ; the cafe is the fame with the alloys 

 of nickel and gold, of lead and gold, of iron and gold ; 

 but the reverfe happens in mixtures of gold with zinc, bif* 

 muth, and tin. It appears, therefore, that the hydrollatic ba- 

 hmce cannot difcover, with certainty, the exadl finenefs of 

 gold, unlefs when filver is the metal mixed with it. 



There are various methods of fcparating gold from gilt 

 works : it may be feparated from the furfaee of filver, either 

 by fpreading over the gilt filver a pafte made of powdered 

 fal ammoniac moiftened with aquafortis, and heating it till 

 the matter i'mokes, and is nearly dry ; throw it into water; 

 and the gold will eafily come off by rubbing it with a feratch 

 brulh : or, by putting the gilt filver into common aqua re- 

 gia, nearly boiling, and turning the metal frequently, till it 

 becomes all over black ; then walh it with water, and rub it 

 with the feratch brufti, which will difengage the gpidleft by 

 the aqua regia. See Gilding. 



Gold may be feparated from gilt copper, by applying a 

 folution of borax to the gilt parts with a pencil, and fprink- 

 ling over the place thus moillened a little powdered fulphur; 

 \vhen the piece is made red-hot and quenched in water, the 

 ^pld may be wiped o'f with a brufh. 



Gold may be recovered from wood, gilt on a water fize, 

 by fteeping, it for a quarter of an hour in a quantity of very 

 hot water, fufficient to cover it ; then fcrub the wood in a 

 little warm w.ater, with fhort ftiflF brittle bruflies of different 

 fizes : boil the whole mixture of water, fi/.e, gold, &c. to 

 drynefs ; make the dry matter red-hot in a crucible to burn 

 off the fize, and grind the remainder with mercury. The 

 gold will be more eafily laid hold of by the mercury, by the 

 addition of fome clean fand. 



Gold, Alchemical Hi/lory of. See Philosopher's Stotif, 

 and Transmutation. 



Gold, jlmalgam of, is a preparation of gold much ufed 

 by the gilders (fee Gilding) ; and it is made by heating 

 fome pure quickfilver in a clean crucible, and adding to it, 

 when it is nearly boiling, about a fixth of its weight of fine 

 gold in thin plates that are hot ; after this mixture has been 

 kept hot for a few minutes, it becomes an homogeneous fub- 

 fiance ; and when cold, it is put into a piece of foft leather, 

 and which is gradually prefied till the fluid part of the amal- 

 gam, confining almoil wholly of mercury, is forced through 

 the pores of the leather ; while the gold, combined with 

 about twice its weight of mercury, will remain in the ftate 

 of a yellow filveiy mafs, of the eonfi Hence of foft butter ; • 

 when this mafs has been bruifed in a mortar, or fliaken in a 

 phial, with repeated portions of iait and water, till the water 

 receives no foulnefs from it, it is fit for ufe, and may be 

 preferved for any time in a corked phial. For the purpofes 

 of gilding it i.s of great importance, that this amalgam- 

 (hould be formed of pure materials, as any portion of lead 

 or bifmuth would deteriorate the colour of the gold, and 

 tarnifh it with black fpecks. The mercury (liould therefore 

 be previoufiy diftilled from the red precipitate (nitrous red 

 oxyd of mercury), either alone or mixed with a httle char- 

 coal powder. See AiMALOAii and Mercury. 



GoLTJ-bealin^, and Gohv-l/cater' s fiin. See GoLv-leaf, 



Gold, Burmjlied, is that which is polifhed with a fteel in- 

 ftrument, called a burnifiier, if it be wrought gold, or gild- 

 ing on metal ; or with a wolf 's tooth, if it be gilding in water. 

 See Gilding. 



Gold Chain: See Chain. 



Gold Coin, or fpecies of gold. See Coin and Coinage. 



Gold Colour on Clafs artd China. See Gems, Glass, 

 GiLDiNti, and Porcelain. 



GoLD-coloured Glazing. See GlazinG. 



GoLD'Colourcd JlTeltil'is produced by melting zinc with cop- 

 per. According to the purity of the zinc and copper, the 

 proportions in which they are mixed, and the intimacy of 

 their union, tl^ compound metal proves more or lefs malle- 

 able, and approaches more or lefs to the colour of gold. 

 Some direft the zinc to be taken only in a fifth or fixth part 

 of the weight of the eepper, and others in an equal weight 

 or more. Dr. Lewis oblerves, from the refult of many ex- 

 periments, that both with the fmallell and largell of thefe 

 quantities of zinc, the metal proves more hke gold than with 

 the inteiTnediate proportions. 



The colour of thefe compounds is improved by a fmall 

 mixture of fome other metallic bodies. Cramer recommends 

 the addition of a fmall quantity of pure tin to copper, melt- 

 ed with a fourth or fixtli part of zinc, which forms a com- 

 pound metal, that acquires, on being well cleaned, and laid 

 in the air for fame days, a fupevficial colour of fine gold; 

 Geoffroy fays that iron has the bell efleft : with the pro- 

 portions of ten parts of zmc, eight of copper, and one, of 

 iron-filings, he produced a metal of a fine fmoolh grain, com- 

 patt, hard, and bright, and of a beautiful gold colour. By 

 making the copper firft into brafs, and then melting it with 

 a fuitable quantity of zinc, a metal may be obtained of fu. 



p'irioiv 



