ON GOLD : ITS FORMATION IN OUR REEFS. 163 



1. — That it is not as free sulphur is evidenced by the fact that 

 boiling ether, or bi-sulphide of carbon — two liquids having con- 

 siderable 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 amalganaate. 



Neither of these liquids liad any effect upon clean gold in regard 

 to its behaviour with mercury. 



2. — That it is not combined with hydrogen, and thus condensed 

 on the gold surface as sulphuretted hydrogen, appeared from the 

 circumstance that sulpurous acid effected no apparent change on 

 it. 



Not appealing to be in either of these forms, I therefore 

 assume it to exist in chemical union with the metal as a sulphide 

 of gold. 



Independent of the proof derived from experiment, it may be 

 expected that sulphur brought into close contact with a metal 

 which we know does form chemical union with it in a wet way, 

 and at common temperatures, would then be in an exti-emely 

 favourable condition for the exercise of chemical affinities ; and 

 the same argument applies for absorption being generally chemical 

 wherever there are affinities existing at the temperatures we 

 employ between the absorbants and the absorbed substances. 



Indeed so far as these experiments and arguments are deemed 

 conclusive in favour of the absorption of sulphur by gold being 

 chemical, by so much are we compelled to diverge from the 

 received opinion that the absorption of the common gases by 

 platina is always a mechanical one, and are compelled to 

 distinguish vai'ieties of absorption. 



The affinities of sulphur, also oxygen, for platina, are superior 

 to their affinity for gold ; why not therefore suppose sub-sulphides, 

 or sub-oxides, to form, when these substances are respectively 

 absorbed ; but the whole question of the.se minute actions of 

 metallic surfaces requires rigorous investigation. 



As I have already said, there is no visible change upon the 

 surfaces of gold treated with sulphuretted hydrogen, not even 

 upon richly argentifei'ous gold. Still the sulphur is there, and as 

 my tests reveal, in chemical combination with the metal ; but 

 some farther confirmation may be considered necessary. Professor 

 Eglinton, of the New York School of Mines, records the fact 

 that he has found gold soluble in cold sodic-sulphide. It will l)e 

 remembered that I have already stated that gold should be soluble 

 in alkaline sulphides, as it is sulphurized by them, and gold 

 sulphide is soluble in them. 



But a more complete confirmation of the correctness of my 

 discovery, that the absorption of sulphur by gold is chemical, has 

 just been obtained experimentally. 



I find that if gold is digested for about eighteen hours in a w^eak 

 solution of sodic and ammonia sulphide, it becomes very 



