140 Observations on the Purity of Standard Gold, 



weight, because it was evidently whitened by the fusion of 

 very minute particle* of silver detached from the small 

 fragment of silver, which was then found adhering imme- 

 diately over the gold, in the form of agglutinated dust : 

 this fragment of silver weighed six grains and one-eighth. 

 We afterwards boiled this gold (which was silvered only 

 6n its surface) for some time in pure nitric acid; when it 

 lost completely its silver colour; and when assayed it was 

 found to be 24 carats. 



We proceeded afterwards to examine the small earth v 

 residue, in which we found, in saline particles, only a 

 few atoms of muriate of soda, and scarce a trace of muriate 

 of copper. The muriate of silver, which, on account of the 

 loss suffered by the piece of silver, ought to have formed a 

 weight of 45 grains and a half, was certainly evaporated with 

 the other elastic vapours. Eleven grains and a half only 

 of muriatic acid concurred in the formation of this muri- 

 ate: the thirteen pennyweights and a half of the same acid, 

 which besides contained the common salts employed in 

 this experiment, have therefore been dissipated (by not pay- 

 ing attention to the little copper) by a decomposition ef- 

 fected by means of the vegetable matter which was joined 

 with it : but what is difficult to account for, and which is 

 foreign to our object, is the evaporation of ten whole pen- 

 nyweights of soda, contained in the common salt, and 

 which ousrht to have remained fixed at the bottom of the 

 vessel: it had therefore become volatile, either by decom- 

 position, or by a new composition, and it had escaped by 

 the aperture in the apparatus. 



It is not probable, therefore, that Philip made use of simi- 

 lar methods of refining, either by flux or by cementation, 

 because, we repeat, he would have reduced the gold to a state 

 of perfect purity, as Darius wished to do subsequently; or 

 he would not have limited himself to so small a portion of 

 alloy, or perhaps this alloy would not have been silver. And 

 if he employed gold in the state in which he found it, we 

 must be forced to admit that nature furnished it at 23 carats 

 and a half fine, or of the standard of (0*979*). 



Many 



* Reaumur says (Memoircs de 1' Acadrmiedcs Sciences 1718, p. 87.) that 

 The gold brought from the bed of the river Ceze is at the standard of IS 

 carats eight grains. 



Gold of the Rhone . . . . . . 20 carats. 



of the Rhine .. .. .. 2}i 



of the Arritge . . . . . . i>'_'f 



Reaumur also observes, that the standard varies in the same piece of na- 

 tive 



