COLD. 



The alloy withplatilia is of a ycUouifli white co'our, very 

 duotili', and of a confiderable fpccific gravity. The alloy 

 witii iilvcr ill the llandarj proportioii, or I to 12, approaches, 

 as we have feen above, the nearefl to the dudtility of hne 

 gold of any alloy, and its fpecific gravity differs but little 

 troin the mean fpecilie gravity of the two metals. When 

 the fdver amounts to Ith, the colour of the allov approaches 

 to green, and forms the green gold of the goldfmiths. In 

 combination with copper, gold has its colour rather 

 heightened than impaired ; its Iiardnefs is increalcd and its 

 ductility very little lelfened, when the llandard proportion of 

 I part in 12 is not exceeded. This alloy of 22 carats fine is 

 generally ufed, when gold is fabricated into plate or orna- 

 ments, and likewife forms the gold coin of the country. 

 With quickfilver, gold unites with great facility, making 

 with it an amalgam which will be defcribed hercatter. The 

 alloy with iron is much harder than gold, very duftile and 

 malleable ; but the colour is debafed to a dullifh grey, inclin- 

 ing to white. Tin was formerly regarded as the metal 

 wliicli rendered the alloy with gold the moil brittle of all 

 the alloys, but the experiments of Mr. Bingley and Mr. 

 HaLchet have fl'.ewn that this notion is to a certain extent 

 erroneous, and that the effects produced by the mixture of 

 till with gold, ought probably to be afcribed to other 

 metals, with which the tin was contaminated, fuch as bif- 

 mnth, antimony, lead, and zinc. The alloy, confifling of 

 equal parts of zinc and gold, is very hard and fufceptible of 

 a tine polifli, and not being fubjeft to much alteration from 

 the air, it is recommended for the fabrication of the mirrors 

 of teleicopes. The alloy of gold with iilver, in which there 

 is onlv .'-th part of lilver, changes the colour of the gold 

 very fenfibly ; and the alloy is employed for foldering gold, 

 being more fuiible than this metal. 



Gold, Phyjual properties of. Gold, auriim, a yellow 

 metal, heavy, pure, ductile, malleable, and Ihining; and on 

 thofe accounts, the moft valuable of all metals. lu fufi- 

 bility it ranks between filver and copper ; it is not oxydable 

 by fufioii in atmofpheric air; nor is it afted upon by any of 

 the acids, except the oxymuriatic and nitro-muriatic> 



The yellow colour of gold is rendered paler by fufion with 

 borax ; but this may be prevented or corrected by fulion 

 with nitre, or fal ammoniac. The colour of gold is 

 heightened by an alloy of copper, and this property of 

 copper has given rife to fundry procefles for exalting the 

 colour of this noble metal. Other metals render it paler. 

 The alchemiils call gold, fol, the fun ; to denote its pre- 

 eminence over the otlier metals, which are called by the 

 names of the planets. Its fymbol, or charaftcr, is O ; 

 which, in their hieroglyphical way of writing, denotes per- 

 fection, liniplicity, folidity, &c. 



The weight of gold is to tliat of water, according to fome 

 ftatements, as 19.637 to 1000. Fine gold, immerfed in 

 water, weighs nearly one nineteenth part leis than in air, 

 and confequently it is upwards of nineteen times heavier than 

 its own volume of water. However, the fpecific gravity of 

 gold, or its comparative weight with an equal volume of 

 water, has been varioully alhgned : fome have made it 

 19.637, others 19.640, and in tlie Swedilh Tranfadtions it 

 is made no lefs than 20.000; that of water being loco. 

 Others again have made it as low as 18.75. ^"^ '"'""'' '^'-' 

 experiments of Mr. Ellicot, it does not appear to have ex- 

 ceeded 19.207 ; and from thofe of Dr. Lewis, on the pureft 

 gold, well iiammered, its gravity is ilated between 19.300 

 and 19.400. In all experiments of this kind, the relnlt 

 fhould be fpecilied with an account of the fenfiblllty of the 

 balance, and the quality and warmth of the water. An in- 

 creafe of heat rarefying water more than it does gold, the 

 Vox.. XVJ. 



gold muR turn nut proportionably heavier tliaii an cqihl 

 volume of tlie exj)iinded fluid ; and this difiereiicc ii nior.; 

 conliderabie than it has generally bei 11 fuppofed. I'^rom 

 freezing to boiling water, or by an augn.entation of heal 

 equivalent to 180 of l"ahrcnheits thermometer, Dr. Lew's 

 found that a rod of gold was lengthcui-d about one part i.i 

 703, and confequently its volume increafed about otic part 

 in 233, while tlie volume of v.ater is increafed one twcnty- 

 fixth or more ; Jieiice it appears, tliat by an ai!grt""T.ati<jn 

 of 40"^ of the thermometer, or from a little above fri-e/.i.ig 

 to the fummer heat, the volume of gold, if its expai;lion he 

 i.niform, is increafed one part in 1048, anil that of v.ater 

 i/ne in 117; and the gravity of gold, weighed in ihc water 

 fo warmed and expanded, Ihould be greater than \y!ien the 

 gold and water are 40 colder, in the proportion of about 

 19.265 to 19.400: and this calculation gives a difference, 

 in the gravity, of O.034 for every 10' of the llicrniomiter ; 

 but fome trials feemed to make it greater. It Iia3 been 

 imagined, that the comparative gravity of gold to brafs 

 weights, which are more than double in volume to an equal 

 weight of gold, mull be lo far influenced by the variable 

 gravity of the atmofphere, that there iiinil be an advantage 

 in buying gold by weight when the air is ligjitefl. Cut Dr. 

 Lewis obferves, that this difference appears too inconf:d-.r- 

 able to be regarded in a commercial view. For the lof;; of 

 weight of the two metals in the air being as much lefs than 

 their lofs in water, as air is lighter than water ; and air, if 

 we admit the accuracy of the conclufion deduced from an 

 experiment of Mr. Hawkibee, being in its lighteft ftate 

 about a 937th, and in its heavieft (late about an 848th part 

 of the weight of water ; it will be found, on calculation, 

 that the gold preponderates above the brafs, in the hcaviefl 

 more than in the Ughtell air, only by one part in 145. oco, 

 or one grain in about 302 ounces ; which is a difference too 

 minute to be feniible in the nicefl balance. If the mean 

 gravity of gold be reckoned 19.3CO, as a cubic inch of 

 ^vater weighs about 254 grains, a cubic inch of gold will 

 confequently weigh about 4902 grains, cr 10 ounces, 102 

 grains. The pound weight, or tv.elve cinccs Troy, of 

 gold, is divided into twenty-four carats. Dr. Lewis Hates 

 tlie fpecific gravity of fine gold at 53 Fahrenheit, to te 

 19.376. According to Briuon the fpecific gravity of fine 

 gold in ingot is 19.258, and when hammered 19 361. 

 The fpecific gravity of gold made ftandard by Britilli 

 copper, was found by Mr. Hatchett (fee Phil. Tranf.^for 

 I'-!o3) to be 17.281, when call in an iron irould ; but 

 when the fame was call in fand, it was only 16.994. . (See 

 Spenfc Gn.^^■ITy.) The foftnefs of gold, for it is nearly 

 as foft as tin, and its toughncfs, adapt it for receiving thi 

 inipivfTions of dies, and of courfe to be reduced to the flate 

 of coin, and for various other purpofes in the arts. It is 

 biU (lightly elaflie and fonorous. \Vith regard to tenacity, 

 it is inferior to iron, copper, platina, and nlver, and there- 

 fore the afiVrtions of fojmer chemills and philofopliers ha\e 

 been contradicted by later exi>*riin.ciits, for gold lias been 

 I'fually reprefeiited as the n.oft tenacious as well as tlie luoll 

 dutlile of all metals. Its malleability and duclility are 

 fufficiently evinced by the GoLD-/f<j/"and GoLD-ww, whicli 

 fee. See alfo Ductility. 



The value of gold to that of filver, was anciently only as 

 twelve to one. Indeed, tliis proportion varies as gold is 

 more or lefs plentiful : for Suetonius relstcs, that C.-cfar 

 brought fuch a quantity of gold from Italy, that the pound 

 of <Told was onlv worth feven pounds and a half of filver. 

 In our coinage, the value of fine gold to fine filver is nearly 

 as 15,- to I. (>'5ee Coin and ST.vsn.Mtn.) Sir Ifaac Ne*-- 

 ton obferves, in a repfefcnlation to the lords of the treafury 

 3 II in 



