Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/775

Rh GOLD piece. to 986'6, that of the Austrian reiehsdueaten, the alloying metal being mainly copper. In England, when gold coins were lirst introduced by Ileiiry III., in 1257, they were of pure gold. l‘]'lward III., in 1345, was the lirst to use a. standard 994's, and in 1526 Henry VIII. issued crowns of the double rose of the standard 916'G for concurrent issue with sovereigns, and other coins of the original standard 994'8. In 1544 the standard for all gold coins 75 1 was reduced to 9166, and again in 1546 to 833%}, the lowest point ever reached in England. Mary restored the old standard 994'8. I Elizabeth directed that coins of both standards, 916'6 and 994'8, should be issued, and the latter was employed at intervals until 1640. Since then the lower standard, 916'6, has been solely used, and, as is shown by the following extract from the Coinage Act of 1870, 33 Vic. c. 10, is the one now in use :— 5 I Staiidard Weight. Least Current Weight. Remedy Allowance. _ Weight. 'cight. Weight. Veight. I _.‘l M._t. - |_ 051m l Grains. Grams. Grains. Grains. Gidiiiisl. Fineness‘
 * 1)ciioi3i)iii:tioii of hnpﬂiul jg];-ic —Imperial __MT-ti-ic-‘ Standard 1-‘ iiicncss. — ‘cig ‘I_1l _ nl
 * Goi.i)— I

Fivc—Pound......... 61637239 39 '9-l0‘?8 61250000 3968935 Elcvcn-twelfths fiiie 1'00000 0 06479 I Two-l’ound ................ .. 24654895 15'97611 24500000 1537574 gold, oiietwclfthalloy; 040000 0 02592 0002 Sovereign. . . . . . . . . . . . . . . . . .. 1‘23“2T-147 7'9S805 1'2'2'50000 793787 or niillesiiiial ﬁneness 0'20000 0'01'296 f llalf-Sovereign. . . . . . . . . . .. 61'63T‘.Z3 3'99-102 61 '12500 306083 916‘66. 010000 0 00648 In Anierica and in those countries which have formed the “ Latin (‘onveiition," the standard of gold coin is 900, with a “remedy” of :i:]'(,-25 5. M. l’eligot suggested‘ that by employing a triple alloy containing 58'1 per cent. of gold, 36'1 of copper, and 5'8 of zinc, a coin might be produced which, while be.iiig of the value of 25 francs, would have the decimal weight of 10 grammes. The alloy is perfectly malleable and of good colour. In England the t"-vllowing standards are used for plate and jewellery, 375, 500, 6:25, 7 3), and 91613, the alloying metal being silver and copper in vary- in; proportions. In France three alloys of the following standards are used for jewellery, 9'20, 840, and 750. A greenish alloy used by goldsmitlis contains 70 per cent. of silver and 30 per cent. of gold. “ Elue gold" is stated to contain 75 per cent. of gold and ‘.25 per cent. of iron. The Japanese use for ornament an alloy of gold and silver, the standard of which varies from 350 to 500, the colour of the precious metal being developed by “pickling” in a mixture of plum—juice, vinegar, and sulphate of copper. They may be said to possess a series of bronzes, in which gold and silver replace tin and zinc, all these alloys being characterized by patina having a wonderful range of tint. The common alloy, Shi-ya-ku- Do, contains 70 per cent. of copper and 30 per cent. of gold ; when exposed ti air it becomes coated with a ﬁne black patina, and is much used in Japan for sword ornaments. Gold wire may be drawn of any :1uality, but it is usual to add 5 to 9 dwts. of copper to the poum .- The “ sold rs " used for red gold contain 1 part of copper and 5 of gold ; for light gold, 1 part of copper, 1 of silver, and 4 of gold. Alloys of Gold and S[lrcr.——Electrui1i, the natural alloy of gold and silver, has already been described, p. 740. Matthiessen ob- s--rved that the density of those alloys, the composition of which varies from -lu-lg,,. to .-u,;.lg, is greater than that calculated fi'oni the densities of the constituent metals. These alloys are harder, more fusible, an-l more soiiorous than pure gold. The alloys of the f<)1'l1111lil3 .iu.g, _»lu.ig._., Auiigj, and AiiAg.m are perfectly honio- geneous, and have been studied by Level." llatcliett has shown,‘ lay a series of careful c.:pcrimcnts, that certain metals, ever) when present in such small quantities as the T,—,‘Wtli part of the mass, render standard gold brittle and unﬁt for rolling. These metals are bismuth, lcad, antimony, arsenic, and zinc. Gulrl mul Z[:zc.—Vitli regard to the latter met-.11, it may be remarked that, although its presence in small quantities renders gold brittle, it may be added to gold in larger quantities without destroying the ductility of the precious metal, for, as has been already stated, Pcligot proved that a triple alloy of gold, copper, and zinc, which contains 5'8 percent. of the last-iianied, is perfectly ductile. The alloy of 11 parts gold and 1 part of zinc is, however, stated to be brittle. /Jul/l and Tz':z-.——-lcliorne5 showed that gold alloyed with 317th part of tin is siilﬁeiciitly ductile to be rolled and stanipe(l into coin, provided the metal is not annealed at a high temperature. The alloys of tin and gold are hard and brittle, and the combination of the metals is attended with eontraetion; thus the alloy SiiAu has a density 14'243, instead of 14'S:-28 indicated by calculation. Mattliicssen and Bose“ obtained large crystals of the alloy Au,Sn_5, having the colour of tin, which changed to a bronze tint by oxidation. Gold and Iron.—I-Iatchctt found that the alloy of 11 parts gold and 1 part of iron is easily rolled without annealing. In these propo_i-tions the density of the alloy is less than the mean of its ronstitueiit metals. Hold and Pallmlizun.—Tliese metals are stated to alloy in all proportions. According to Clicncvix,7 the alloy composed of equal parts of the two metals is grey, is less ductile than its constituent metals, and has the speciﬁc gravity 11'08. The alloy of 4 parts of gold and 1 part of palladium is white, hard, and ductile. Graham has shown“ that a wire of palladium alloyed with from 24 to 25 parts of gold does not exhibit the remarkable retraction which, in pure palladium, attends its loss of occluded hydrogen. Gold and Platz'mmz.—Clai'kc states that the alloy of equal parts of the two metals is ductile, and has almost the colour of gold. Gold and I2hodimn.—Gold alloyed with %,th or 11th of rhodium is, according to ’ollaston, very ductile, infusible, and of the coloui‘ of gold. Gold and I;-i(lium.—Small quantities of iridium do not destroy the ductility of gold, but this is probably because the metal is only disseminated through the mass, and not alloyed, as it falls to the bottom of the crucible in which the gold is fused. Gold and l'iclccl.—Eleven parts of gold and 1 of nickel yield an alloy resembling brass. Gold and C'oball.—Eleven parts of gold and 1 of cobalt form a brittle alloy of a dull yellow colour. Assay of G'olcl.—1t may be well to supplement the information given in the article ASSAYING with some additional details as to the assay of gold bullion, as practised in the Royal Mint, and of gold ores. The assay of bullion consists of six operations:— (1.) The sample of metal taken for assay is ﬂattened, and an assistant adjusts a portion of it to an exact weight by cutting or filing. This weight varies with different operators from 5 to 16 grains. The assayer then completes the adjustment on a more sensitive balance. The prepared assay piece is wrapped in lead foil, together with a certain amount of pure silver, which is generally equal to 2;: times the amount of gold assumed to be present. In the case of standard gold, the weight of lead employed is to the weight of the alloy taken for assay as 8 to 1, and the ratio of the weight of lead to the weight of copper present is 100:1. Much diversity of opinion exists as to the amount of lead that should be employed. The pro- portions recommended by D’Arcet9 are considerably less than those advocated by Kaiidclliardt ;1° and it may be stated, with regard to the silver, that the last mentioned authority and Cliaudet recommend the proportion of 1 of gold to 2; of silver, but Pettcnkofer states that the proportion need not exceed 1 to 1§, provided that the subsequent boiling in nitric acid is sufficiently prolonged. The amount of gold lost in ciipellatioii has been shown by I-lossler to increase with the amount of lead used, and to decrease as the amount of silver is increased.“ (2.) The necessary number of cupels are arranged on the bottom of the miifﬂe (ﬁg. 2, ASS.-YI.'G), and the packets coiitaiiiiiig the silver and gold are transferred from a. numbered wooden range to corresponding eupels. The furnace operations are then performed as is described in AssAYi.'G (p. 727), and the result is that each cupel contains a button of silver and gold. (3.) The button a (ﬁg. 11) is ﬂattened by striking it with a hammer on a polished anvil, first in the centre, and then on the edge, a third blow being given on the opposite edge which clongates the metal. After annealing in an iron tray. the flattened buttons b are reduced by laminating rolls to the thiekness of a visiting card c. They are again annealed and rolled into a spiral or cornet_d. (4.) These comets are then treated with nitric acid of speciﬁc gravity 1'2, either separately in parting ﬂasks, or together in cups 1 Comptes Remlus, t. lxxvi. p. 144]. -' L'rc‘s Dictionary of Arts. 7th edition, 1S7-3. vol. i p 96. -‘ .lmi. tie (,'}ii'm. rt dc Phys. (3). t. xxxvi. p. 193, and t. xxxix. 1. 16:‘-. 4 mu Tr(ms.. 130:1. part 1, pp. 43-194. -" I'M’. Trans, 1734. ‘- l‘ro¢‘. Roy. Soc, vol. xi. 1860-2, p. -1311 7 Wurtz. Dic!io;1nm're cle Clu'1m'e, t. ii. p. 630. “ Proc. Roy. Soc. xvii. p. 503. __ _ _, 9 Bodemann‘s Anleitumv zur Berg- und I1iil(enniann1schen 1’robzcrl'mis(, ‘.41 ed. 1s:.6. p. 360. W Go rl-Probirretfalzrcn. p. 3. " lringl. Polylech. Journ., 206, p. 18-}.
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