GOLD. 



quantity ; but It is a common error of 

 chemical writers, to say that the slightest 

 addition is sufficient for this purpose. 

 "When alloyed with tin, however, it will 

 not bear a red heat. With iron it forms 

 a grey mixture, which obeys the magnet. 

 This metal is very hard, and is said to be 

 much'superior to steel for the fabrication 

 of cutting instruments. Bismuth renders 

 gold white and brittle ; as do likewise 

 nickel, manganese, arsenic, and antimo- 

 ny. Zinc produces the same effect ; and, 

 when equal in weight to the gold, a me- 

 tal of a fine grain is produced, which is 

 said to be well adapted to form the mir- 

 rors of reflecting telescopes, on account 

 of the fine polish it is susceptible of, and 

 its not being subject to tarnish. The al- 

 loys of gold with molybdena are not 

 . known. It could not be mixed with tung- 

 sten on account of the infusibility of this 

 ]ast substance. Mr. Hatchett gives the 

 following order of different metals, ar- 

 ranged as they diminish the ductility of 

 gold : bismuth, lead, antimony, arsenic, 

 zinc, cobalt, manganese, nickel, tin, iron 

 platina, copper, silver. The first three 

 were nearly equal in effect ; and the pla-. 

 tina was not quite pure. 



For the purpose of coin, Mr. Hat- 

 chett considers an alloy of equal parts 

 of silver and copper as to be preferred, 

 and copper alone is preferable to silver 

 alone. 



Gold is found mostly in the metallic 

 state, .though generally alloyed with sil- 

 ver, copper, iron, or all three. It is found 

 either in separate lumps, or visible grains, 

 among the sands of rivers, in many parts 

 of Europe and elsewhere. The quantity 

 is, for the most part, insufficient to pay 

 the cost of separating it; but it is thought 

 to be more universally diffused in sands 

 and earths than any other metal, except 

 iron. The greatest quantity of gold is 

 imported into Europe from South Ame- 

 rica. Some is brought from the East In- 

 dian islands and China, and some from 

 the coast of Africa. The principal gold 

 mines in Europe are those of Hungary. 

 Some sands afford gold by simple wash- 

 ing ; the heavy metallic particles subsid- 

 ing soonest: but when it is bedded in 

 earths, or stones, these substances are 

 pounded, and boiled with on.e-tenth of 

 their weight of mercury together with 

 water. The mercury, after a certain 

 time, absorbs the gold, and may be sepa- 

 rated by pressure through leathern bags, 

 and subsequent distillation Or, other- 

 wise, if the sand be heated red hot, and 

 quenched in water several times, for the 



purpose of cracking and dividing it, and 

 the whole be then melted into glass, with 

 twice its weight of the oxide of lead, call- 

 ed litharge, and charcoal powder be then 

 added, the lead will be revived in the me- 

 tallic state, and will carry the gold along 

 with it. By exposure to a proper degree 

 of heat, with access of air, the lead may 

 again be converted into litharge, and the 

 gold will be left pure. This last opera- 

 tion is, in fact, a method of assaying sands 

 which contain gold, rather than of obtain- 

 ing it from them in the large way. 



Gold. is also found in certain martial 

 pyrites in Sweden and elsewhere ; from 

 which it may be extracted by torrefaction, 

 or burning of the sulphur, and subsequent 

 digestion in aqua-regia. 



To obtain gold in a state of purity, or to 

 ascertain the quantity of alloy it may con- 

 tain, it is exposed to a strong heat, toge- 

 ther with lead, in a porous crucible. This 

 operation is called cupellation. 



After gold has passed the cupel, it may 

 still contain either of the other perfect 

 metals, platina or silver. The former is 

 seldom suspected ; the latter is separated 

 by the operations called quartation and 

 parting, For all these operations, see AS- 

 SAYING. 



The quantity of alloy is never consi- 

 dered as part of the value of metals which 

 contain either gold or silver. In estimat- 

 ing or expressing the fineness of gold, 

 the whole mass spoken of is supposed to, 

 weigh 24 carats of 12 grains each, either 

 real or merely proportional, like the 

 assayer's weights; and the pure gold 

 is called fine. Thus, if gold be said to be 

 23 carats fine, it is to be understood 

 that, in a mass weighing 24 carats, the 

 quantity of pure gold amounts to 23s 

 carats. 



In such small works as cannot be as- 

 sayed by scraping off a part, and cupel- 

 ling it, the assayers endeavour to ascer- 

 tain its quality or fineness by the touch. 

 This is a method of comparing the colour 

 and other properties of a minute portion 

 of the metal with those of certain small 

 bars whose composition is known. These 

 bars are called touch-needles ; and they 

 are rubbed upon the black basaltes,which, 

 for that reason, is called the touch-stone. 

 Black flint, or pottery, will serve the 

 same purpose. Sets of golden needles 

 may consist of pure gold ; pure gold 

 twenty-three and a half carats with half 

 a carat silver ; twenty-three carats gold 

 with one carat silver ; twenty -two and a, 

 half carats gold with one and a half carat 

 silver, and so forth, till the silver amounts. 



