218 



upon many samples of native gold, and the certainty that one or other of the 

 sulphui'izing agents specified does frequently occur naturally in metaliferous 

 rocks, it seems highly probable that a large area of the natural surfaces of 

 native gold is sulphurized, and thus rendered, according to the degree of this, 

 non-amalgamable . 



If this is so, a very sufficient cause appears for the heavy loss in the 

 precious metal, experienced by the mill-owners in working their auriferous 

 reefs by the amalgamation process, since it would only be those portions or 

 grains thus suliohiirized, which have chanced to get their surfaces abraded 

 during their extraction or milling, that would be at all likely to adhere to the 

 mercury used. 



Whether this absorption is a purely mechanical one, as is assumed for that 

 where platinum acts upon sulphuretted hydrogen and other gases, or whether 

 it is a truly chemical one, is a matter of some interest to enquire into, 

 particularly in connection with the, as yet, ixnsolved problem relative to the 

 mode of solution and deposit of native gold ; also, in relation to the question 

 of absorption generally. 



By what can properly be deduced from the facts above stated, and those 

 which have manifested themselves to an investigation canned on especially to 

 determine this point, it certainly appears that this absorption is the; effect of 

 chemical action. 



Thus, if this absorption is mechanical, the sulphur must be in one of the 

 two following conditions : — 



I. As free sulphur. 

 II. Combined with hydrogen, as sulphuretted hydrogen. 



I. That it is not as free sulphur was evidenced by the fact that boiling 

 ether or bi-sulphide of carbon — two liquids having considerable affinities for 

 sulphur — would not remove it from the gold ; for, after long contact with these 

 solvents and an after thorough washing, the gold still refused to amalgamate. 



Neither of these liquids had any effect upon clean gold in regard to its 

 behaviovir with mercury. 



II. That it is not combined with hydrogen, and thus condensed on the gold 

 surface as sulphuretted hydrogen, appeared from the circumstance that 

 sidphurous acid effected no apparent change on it ; the action of this acid on 

 sulphuretted hydrogen being a rapidly decomposing one, sulphur being 

 liberated in a free state, caj^able of being detected and identified as in this 

 state, which I could not accomplish. 



Not appearing to be in either of these forms, therefore we must assume it 

 to exist in chemical union with the metal as a sulphide of gold, forming a 

 film of true auriferous pyrites, as was first suggested to me by Dr. Hector. 



Independent of the proof derived from experiment, it may be expected 

 tnmi sixlphur brought into close contact with a metal which we know does 



