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form chemical union with it in a -wet way, and at common temperatures, would 

 then be in an extremely 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 these arguments are deemed con- 

 chisive 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 platinum is always a mechanical one, and are com- 

 pelled to distinguish varieties of absorption. 



The affinities of sulphur, also oxygen, for platinum, 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 

 these minute actions of metallic surfaces requires rigorous investigation, and 

 for this 1 doubt not the mercury test here used for proving absolute cleanliness 

 of surface will often prove very useful. 



Reverting to that which more strictly falls within the scope of this paper, 

 as sulphur has been found upon native gold, I should be quite prepared to 

 find the metals tellurium and selenium also upon the natural surfaces of the 

 gold of Transylvania and the Thames (these substances being isomorphous 

 with sulphur and more fixed), as telluric gold is found in Transylvania^ and 

 the character of the two golds assimilates. 



In conclusion, I would beg to observe the necessity of fully establishing 

 the character of this absorption of sulphur by gold. If it is a chemical act, as 

 present evidence tends to show, and sulphides of gold and platinum are so 

 easily and so rapidly formed, we cannot doiibt but that sulphur plays a very 

 important part in the solution and translation of these metals from rock 

 masses to intersecting quartz reefs, or from deep strata to superficial positions. 



In whatever form, however, sulphur is thus absorbed by gold, it is 

 certainly the greatest obstacle to a thorough and complete amalgamation which 

 we have to contend with ; no doubt other substances occasionally intervene 

 to prevent or retard this process, such for instance as the oxides of iron and 

 organic matter, but sulphur and its isomorphs must, I think, be the most 

 actively and the most frequently concerned in this refusal of natixral gold 

 surfaces to amalgamate. In case further investigation should prove this 

 sulphurization of the natural surfaces of gold to be general, it will be easy to look 

 for a remedy against its effects ; but, as yet, it would be useless to speculate 

 as to what this should be. As stated, there are several ways of removing 

 these films : perhaps chloride of lime in conjunction with muriatic acid would 

 prove serviceable, but, unfortunately, it could only be applied to the "stuff" 

 before amalgamation, and there might be a loss of gold occasioned by solution. 



The sodium amalgam of Crooke would be a safe and certain remedy, and 



