391 Transactions. — Chemistry. 



are somewhat difficult to oxidize can absorb H 2 S, for instance, silver, 

 mercury, gold, and platinum. It is further known that the removal is, in 

 these cases, chemically brought about, the sulphur of the gas combining with 

 the metal forming a true sulphide ; why not, then, continue the analogy of 

 graphitic carbon with these metals, by supposing that the absorption of this 

 gas by such carbon is also a chemical action resulting in the formation of a 

 sulphide of carbon analogous in some measure with the sulphides of the metals 

 instanced ? We can suppose that, according to the proclivities of these 

 sulphides, they may be hydrous or anhydrous, but any way we must account 

 for the hydrogen dissociated from the sulphur in this absorption, and this we 

 cannot do better, I think, than by supposing it combined with oxygen to form 

 water, free or combined, according as the sulphides are anhydrous or not. 



I cannot see but that this is a legitimate conclusion; and though it would 

 |be very difficult to prove by analytical results that such is the case, it would, 

 I believe, be quite as difficult to prove the reverse. 



It may be averred, in response to this, that there is no physical change 

 manifested in the carbon, and that the absorption is slight as computed upon 

 the weight of solid material used ; but we must consider that physical 

 change, of a magnitude so great as to manifest itself to us, is not necessarily 

 the consequence of even a profound chemical change in structure or composi- 

 tion. The sulphurizing of gold or platina for instance at common temperatures 

 by the gaseous method does not exhibit itself optically, nor even gravimetri- 

 cally to any ordinary weighing apparatus, yet the surface of these metals can, 

 as we know, be covered with the compound thus formed, and so completely 

 that they will not amalgamate while in this condition. 



Again we must consider that the comparatively small extent to which this 



absorption can be carried on may be due to carbon being less quantivalent 



when in the graphitic or metallic state than it is now assumed to have, this 



being certainly computed for it as existing in the metalloidal state. Further, 



we know that hydrogen and other elements form a notable part of most 



graphitic carbons, especially of charcoal, and as these are, without doubt, in 



greater part combined with the carbon, we may have a compound to deal with 



in place of an element, and so a substance having yet a higher atomic 



equivalent. Besides, the greater part of this compound may, like that of gold 



and platinum with sulphur, be so situated as to be out of contact with the 



gas; also, the sulphuretted compound thus formed is possibly so firmly 



adherent to the carbon that it cannot scale off and so expose fresh surfaces 



(as rust of iron does), and it may be so insoluble in the menstruum in 



which the gas is administered that the thinnest films of this compound 



upon the carbon act as an effectual bar to further action of this kind, 



graphitic carbon in these particular relations of it to sulphur occupying in 



