Observations on the Purity of Standard Gold. 13<> 



the barley, or the barley meal, was used instead of charcoal, 

 in order to form what the Lyonnese call the soul of the 

 crucible, which was placed at the bottom of it, where it was 

 retained by a covering (from which probably comes the 

 expression of dosed crucible), on which i he 'gold in fusion 

 was placed by means of a little lead (in order to vitrify the 

 base metals which it might contain,) and some common 

 salt, sulphurct of antimony or of lead, in order that 

 they may lay hold of the fine silver and volatilize it with 

 the lead, or reduce it to scoriae. The elastic fluids, extri- 

 cated from the vegetable matter by the action of the fire, 

 form the office of bellows for incessantly agitating the 

 metal during several days, which makes all the impurities 

 swim above, and which ought to be skimmed off as the 

 Lyonnese do. 



Properly speaking, a fire which lasts five days gives ra- 

 ther an idea of the cementation of the moderns, and ana- 

 logous to that which Pliny has communicated to us, than 

 a real fusion in close crucibles, — a circumstance which 

 would be directly contrary to the object in view. Thus, in 

 Hungary, in order the better to open all the interior parts 

 jof the gold to the muriatic acid reduced into vapour in the 

 cementation, they are accustomed to add lead to the mass, 

 which is afterwards reduced into small hollow drops, or, in 

 other words, into grains. It may be that the lead indi- 

 cated by Agatharchides has the same object: the tin may 

 have been taken by an equivoque for crude antimony, for 

 galenum, or for -the native sulphuret of lead: it is possible 

 likewise that the barley meal was merely intended to serve 

 for the equal distribution of the little salt, a stratum of 

 which must be placed on the gold, and perhaps assisted to 

 decompose it, as argil or sulphate of iron now does. 



In order to obtain some light upon this curious subject, 

 there were put into a crucible covered by another crucible 

 turned upside down, thirty pennyweights of barlev-meal, 

 and an ounce of common salt: it was then made red-hot, 

 and kept 3r3 hours in this state. Tbe.e was put in, more 

 for the sake of curiosity than any thing else, a thin piece of 

 gold weighing 24 grains, and a piece of silver weighing 40 

 grains. The lower crucible was half full, and an opening 

 was left at the joining of the two crucibles to let out the 

 elastic vapour. 



After this space of time, the apparatus being cooled was 

 opened, and there was found a small earthy residue slightly 

 saline and whitish, weighing eleven grains and a half. The 

 gold was above; it was increased one eighth'of a grain in 



weight, 



