926 Transactions of the American Institute. 



iiue charcoal dust and plumbago, an equal quantity of each, placed 

 into a carbon crucible, and this into a porcelain retort, which has a 

 tube attached, through which the gases that escape during the 

 heating of the crucible can be passed into a chlorine solution. 

 "VN^ien the crucible is slowly brought to a red heat, bisulphide of 

 carbon issues forth, and at the same time the chlorine solution 

 darkens; when tested with sulphate of iron or oxalic acid, a pre- 

 cipitate of gold is obtained. This volatilized gold is not absorbed 

 by mercury. If the desulphurized remaining ore is then again 

 treated with mercury vapor, as before, cooled and washed, a third 

 quantity of gold is separated. 



This, and a number of other observations have brought me to 

 think that gold was, and still is, existing in nature in a chemically 

 combined state, not only with sulphur, but also with silica as a 

 silicate of the oxide of gold Au O Si O^, as a silicide of gold Au Si, 

 and, perhaps, in many other similar combinations. I ask you 

 simpl}', my hearers, did we ever look for gold in a different state 

 from the metallic? We speak of invisible gold, prepare in our 

 laboratories solutions of gold, auric oxides, suli^hides, and other 

 combinations, and deny to nature, whicji we only imitate, the right 

 and privilege to have used the same means, simply because our 

 books say otherwise or nothing of it. Why can we not oxidize 

 gold in its metallic state without first dissolving it ? I think it is 

 simply for the reason that it has to be brought to an atomic, amor- 

 phous state, and subdivision, before it is acted upon by oxygen or 

 sulphur. 



Rose-colored quartz is by miners considered quite a reliable indi- 

 cation that gold may be expected at greater depth. By smelting 

 glass with purple of cassius, oxide of gold, auric acid, or even 

 finely divided precipitated gold, we produce a splendid crimson 

 glass, which, if a smaller quantity is used, has the color of rose. 

 If rose-colored quartz is chemically decomposed with fluoride of 

 calcium, gold can easily be detected in the result. I have wit- 

 nessed many experiments, and made myself, M'hile in Bostoli, a 

 number of tests with various fluorides, such as cryolite, fluorspar, 

 and the so-called Stevens flux, all ffivino: me the evidence that the 

 opinion expressed by Prof. Bischoft' in Bonn, the best authority we 

 have in chemical geology, that gold, as well as platinum, may derive 

 its origin from the decomposition of silicates, is well founded. 



We will now take up the next point, and give a brief account of 

 the 



