HISTORY OF GOLD. 539 



its phlogiston ; and IMacquer could do no less than take this Macquer. 

 side of the question. It appears, however, observed he, that 

 it is a kind of calcination which renders gold fitted for becom- 

 ing vitrified. 



Others, with Orschal at their head, seeing on one hand the Orschal. 

 facility with which gold simply attenuated produces this 

 colour ; and on the other, the low tcmpeiature at which its 

 oxides return to the metallic state, concluded, that to divide 

 it well, was suflficient to render it fit for painting. Macquer Macquer. 

 himself at length adopted this opinion, and is the first who 

 said clearly, " all these facts prove, the purple colour is 

 ** natural to gold, whenever it is in a btate of extreme divi- 

 " sion." If it be hereafter discovered, that this doctrine is well 

 founded, let it not be forgotten in France, that to INlacquer the 

 hono'ir is to be ascribed.* 



I will recall, to the attention of chemists, some facts, which 

 may guide us to the opinion, apparently the more accurate of 

 the two. 



Silver is incapable of being oxided by the simple heat of our properties of 

 furnaces; and its extreme readiness to return to the metallic ^''^*-'^" 

 state, when it has been oxided by acids, is another obbtacle to 

 overcome. Yet, when an easily vitrifiable substance cart dis- 

 solve the oxide as fast as it forms, the oxidation, favoured by 

 this attraction, becomes permanent, and supports a heat which 

 is no longer capable of reducing it. The application of leaf Oxide of ^old. 



silver on glass, its oxide combmes with phoshoric or boracic '"f^ ^1 issoU- 

 o ' 1 ed in glass. 



acid, are known proofs of this. The case appears to be the 



same with gold. If a vitreous surface can disstilve its oxide as 



fast as it is formed, the reduction is delayed, and the purple 



maintains itself, till a higher temperature forces it to give up 



its oxigen. 



But the following fact, known in glass-houses, seems to de- CoU] nnitts 



decide the question. Dissolve in soft dint-glass any preciintute "1*^1^ glass, 



^ . ft 7 I i Without colour 



of gold, the result will be a brilliant glass, perfectly transpa- ii,g it. 



* To ascribe to Macquer the honour of a discovery, wliich, ac- 

 cording to our author, yet remains to be made, and respecting 

 which he confesses Macquer only adopted the opinion of otiiers, 

 shows Prof. Proust to be more zealous for the honour of France, 

 than for the cause of truth and justice. — T. 



X X 2 rent 



