GOLD. 



doubt that a complete examination of the 

 process would indicate others worthy of 

 notice. 



Ether, naphtha, and the essential oils, 

 take gold from its solvent, and form li- 

 quors which have been called potable 

 gold. The gold which is precipitated by 

 evaporation of these fluids, or by the ad- 

 dition of sulphate of iron to the solution 

 of gold, is of the utmost purity. 



In the dry way, gold resists the action 

 of neutral salts, more especially nitre, 

 which deflagrates with the imperfect me- 

 tals. Nitre, however, does not afford an 

 expeditious way of purifying gold, be- 

 cause this metal in some measure protects 

 and covers the alloys from its action. It 

 is remarked that borax, used as a flux witli 

 gold, renders it paler ; and that this alter- 

 ation of colour disappears by the addition 

 of nitre or commou salt. As the acid of 

 borax forms a compound with gold, which 

 falls to the bottom when this acid is added 

 to the metal in solution, it is probable that 

 the paleness produced by borax may arise 

 from the combination of a small portion of 

 its acid with the gold, which might be 

 driven off* by a continuance of the heat, 

 and united by stronger affinity with the 

 alkali of the nitre, or of the common salt, 

 in proportion as their acids are dissipated 

 by heat. 



Earth and alkalies do not act on gold 

 in the dry way. Sulphur, which com- 

 bines with most metals, has no effect on 

 this. A process, called dry-parting, is 

 grounded on this property ; and is more 

 especially used in separating silver from 

 gold, when the quantity of the latter 

 metal is too small to answer the expense 

 of dissolving the larger mass of silver in 

 nitric acid. For this purpose the mixed 

 metal is fused, and flowers of sulphur 

 thrown on its surface. These combine 

 with the silver in the form of a black sco- 

 ria, while the gold remains at the bottom 

 in its metallic state. The operation of 

 dry-parting does not leave the gold in a 

 state of purity ; because the last portions 

 of silver are defended from the action of 

 the sulphur. But when the quantity of 

 silver is thus diminished, the operation of 

 parting with aqua-fortis, or nitric acid, 

 may be advantageously used. 



Sulphuret of potash dissolves gold in 

 (lie dry way. Equal parts of sulphur and 

 potash are hastily fused with one-fourth 

 of apart of gold leaf. This combination 

 is soluble in water, with which it forms a 

 yellowish green solution. By the addi- 

 tion of an acid, the gold is thrown down in 



combination with the sulphur, of which it 

 may be deprived by heat. 



Most metals unite with gold by fusion. 

 With silver it forms a compound, which 

 is paler, in proportion to the quantity of 

 silver added. It is remarkable that a cer- 

 tain proportion, for example, a fifth part, 

 renders it greenish. From this circum- 

 stance, as well as from that of a consider- 

 able proportion of these metals separating; 

 from each other by fusion, in consequence 

 of their different specific gravities, when 

 their proportions do not greatly differ, it 

 should seem that their union is little more 

 than a mere mixture without combina- 

 tion ; for, as gokl-leaf transmits the green 

 rays of light, it will easily follow that par- 

 ticles of silver, enveloped in particles of 

 gold, will reflect a green instead of a 

 white light. 



A strong heat is necessary to combine 

 platina with gold: it greatly alters the 

 colour of the gold if its weight exceed 

 the forty-seventh part of the mass. Mr. 

 Francillon, however, informs us, that sir 

 parts of gold and one of malleable platina 

 produce a metal of a beautiful colour, 

 great malleability, susceptible of a fine 

 polish, and more unalterable than gold 

 itself. It does not much affect the duc- 

 tility. The Spanish ministry has prohibit- 

 ed the exportation of platina from Ame- 

 rica, lest it should be used in adulterating 

 gold ; but this does not appear to be % 

 danger which need be feared, as chemis- 

 try has long been in possession of several 

 simple and expeditious methods of detect- 

 ing this fraud, which besides is evident 

 to the sight when the quantity of de- 

 basement is considerable. It may be 

 questioned, likewise, whether the value 

 of platina would not soon equal that of 

 gold, if its properties and uses were bet- 

 ter known in society. Gold made stand- 

 ard by platina, and hammered, is tolera- 

 bly elastic. 



Mercury is strongly disposed to unite 

 with gold, in all proportions with which 

 it forms an amalgam : this, like other 

 amalgams, is softer, the larger the pro- 

 portion of mercury. It softens and 

 liquifies by heat, and crystallizes by 

 cooling. 



Lead unites with gold, and considera- 

 bly impairs its ductility, one-fourth of a 

 grain to an ounce rendering it complete- 

 ly brittle. Copper renders gold less duc- 

 tile, harder, more fusible, and of a deep- 

 er colour. This is the usual addition in 

 coin, and other articles used in society. 

 Tin renders it brittle in proportion to its 



