Temperature of Sublimation. 867 



both are present, by properly regulating the temperature ; 

 the sulphur passing on at a considerably lower temperature 

 than what is required to dispel the deposit of arsenious 

 oxide. 



Sulphur. 



In contrast with the behaviour of the compounds of arsenic 

 the sulphides show a remarkable sameness in the temperature 

 of sublimation however diverse the nature of the molecule or 

 of the associated elements. 



Table III. 



t°. 



1. Molybdenite. MoS 2 . Loc. ? 450 



2. Pyrites. FeS 2 . Loc.? 450 



3. Marcasite. ,, Jasper Co 440 



4. Hauerite. MnS 2 . Eadusa 450 



5. Stannite. Cu 2 S,~FeS, SnS 2 . St, Agnes, Cornwall 460 



6. Chalcopyrite. " Cu 2 S, Fe 2 S s . Loc? 470 



7. Chalcosite. Cu 2 S, Cornwall 490 



8. Linnasite. CoS, Co 2 S 3 . Mnssen 480 



9. Sphalerite (5). ZnS. Various 610 



10. Pentlandite. 2FeS, NiS. Lillehammer 480 



11. Oovellite. CuS. Butte 400 



12. Galenite. PbS. Loc? 470 



13. Bornite. Cu 2 S, CuS, FeS. Audley Mine, Cork 430 



14. Sternbergite. Ag 2 S, Fe 4 S 5 . Konigsberg 170 



15. Sulphur. 60 



16 & 4. Hauerite (trace of free S) 60 



Of the several compounds examined above, sternbergite 

 alone (14), departs from the general uniformity of tem- 

 perature ; possibly because the structure of the molecule 

 Fe 4 S 5 may be a loose one. Sphalerite is exceptionally high. 

 All the substances sublime far above the sublimation tem- 

 perature of the free element. Flowers of sulphur tested 

 under the same conditions gives a sublimate at 60°. 

 It is perhaps open to us to refer such substances as RS, 

 As 2 S 3 to the sulphur division and class them as a low- 

 temperature division. But the fact that such analogous 

 compounds as Cu 2 S, Fe 2 S 3 (6) and CoS, Uo 2 S 3 (8) maintain 

 a high temperature of sublimation is rather opposed to this 

 procedure and suggests that the instability of the As 2 S 3 

 molecule is more fitly regarded as due to the arsenic. The 

 question is, however, not without obscurities. 



