[ 315 ) 



CHAP. V. 



GILDING IN OR MOULU; USE OF QUICKSILVER IN EX- 

 TRACTING GOLD AND SILVER FROM EARTHS; EXPE- 

 RIMENTS OF BOERHAAVE ON QUICKSILVER; SILVER- 

 ING LOOKING-GLASSES, AND THE TIME WHEN THAT 

 ART WAS DISCOVERED. 



J. HERE is another method of applying gold on copper or silver, 

 which is much practised ; it is called gilding in Or Moulu. Quick. 

 silver dissolves gold with great facility : if you spread a gold leaf 

 (not what is called Dutch leaf, which is made of brass) on the 

 palm of your hand, and pour a little quicksilver upon it, you will 

 see the quicksilver absorbing the gold, just as water absorbs 

 into its substance a piece of salt or sugar. Persons who have 

 taken mercurial preparations internally, seldom fail to observe the 

 readiness with which the mercury transudes through their pores, 

 attaching itself to the gold of their watches, rings, sleeve-buttons, 

 or ear-rings, and rendering them of a white colour. A piece of 

 gold, of the thickness even of a guinea, being rubbed with quick- 

 silver, is soon penetrated by it, and thereby made so fragile, that 

 it may be broken between the fingers with ease : and if more 

 quicksilver be added, the mixture will become a kind of paste, of 

 different degrees of consistence according to the quantity of quick, 

 silver which is used. A piece of this paste is spread, by ways well 

 known to the artists, upon the surface of the copper which .1 to 

 be gilded in or moulu, and the metal is then exposed to a proper 

 degree of heat : quicksilver may be evaporated in a far less decree 

 of heat, than what is required to melt either gold or cupper ; 

 when therefore the mixture of gold and quicksilver is exposed to 

 the action of fire, the quicksilver is driven off in vapour ; and the 

 gold, not being susceptible of evaporation, remains attached to the 

 surface of the copper, and undergoing the operations of burnish- 

 ing, &c. too minute to be described, becomes gilt. This method 

 of gilding copper, by means of quicksilver and gold, was known 



