686 . PHILOSOPHICAL TRANSACTIONS. [aNNO 1779. 



common of all ores, and on examination is very seldom found to contain gold. 

 Specimens however have been found from which gold has been procured ; and 

 particularly there have been found in Fatchobuigna near Zalatna, in Transylva- 

 nia, masses which contain a large proportion of this metal. Sometimes the gold 

 is in its metallic form, and visible to the naked eye ; sometimes it is not: and 

 in these cases the ore has been thought to contain the gold united first with 

 iron, and that compound united with sulphur. 



Dr. Fordyce observes on this proposition, that it has not as yet been proved, 

 that a compound metal can be combined with sulphur. If 2 metals are soluble 

 in sulphur, and each be separately combined with it, the 2 compounds may be 

 diffused through one another, as is the case with the compounds of sulphur and 

 iron, and sulphur and copper ; which may be diffused through each other : but 

 if we have a compound of 2 metals, of which one is soluble in sulphur, and the 

 other is not, if we apply sulphur to this compound, it will dissolve the one, and 

 leave the other ; as, if gold and silver be combined, if we reduce the mass to 

 fine particles, and mix them with sulphur, and throw them into a crucible, 

 heated white hot, and afterwards melt the whole mass, the silver will combine 

 with the sulphur, and the gold will fall to the bottom of the vessel. This being 

 the case, they doubted whether this ore contains the gold in its metallic form, 

 only mechanically mixed with the pyrites ; or combined with the sulphur by 

 means of the iron : and therefore subjected a specimen to examination, in 

 which they could not discover, even by the help of a microscope, any particle of 

 native gold. 



Exp. 1. They powdered 100 grs. of this ore, and boiled it in nitrous acid 

 diluted with water; a solution took place with effervescence. Having digested 

 them together, till the whole soluble part was taken up, and poured off the 

 solution, and made a precipitation by fixed vegetable alkali, the precipitate 

 appeared to be iron. Having washed the remaining part with water, and 

 exposed in a glass matrass in sand, to nearly a red heat, a very small portion of 

 sulphur sublimed; the remainder was quartzose sand, with particles of gold, 

 whjch were similar in figure, though small, to the particle of gold found native 

 in veins mixed with various matrixes, and not at all like particles which had 

 been combined with a menstruum, which ought either to have appeared in a 

 powder, whose particles were hardly visible from their smallness; or in crystals 

 similar to one another. 



Exp. 2. If any metal be combined with sulphur, mercury will not precipitate 

 the sulphur from it; they therefore took 140 grs. of the same ore, aud triturated 

 it for some hours with about 5 times its weight of mercury; the powdered ore 

 was washed off from the mercury, the remainder put into glass vessels, and eva- 

 porated by heat : a mass of gold was left, but part of it being accidentally lost, its 



