2 Prof. J. Joly on the 



at was that a compound of antimony of the form n RS, 

 >ttSb 2 S 3 becomes unstable in presence of oxygen at a 

 temperature which is unaffected by the nature of R or by 

 the value of n or m. In fact all these bodies give off their 

 antimony at a temperature varying not very widely around 

 480° 0. Judging from the five observations on other com- 

 pounds of antimony, these bodies also break up near this 

 temperature, whether sulphur is present or not. 

 The new results are as follows : — 



Table I. 



t°. 



1. Andorite. Ag 2 S, 2 PbS, 3 Sb 2 S 3 . Oruro 510 



2. Kerinesite. Sb 2 3 , Sb 2 S 3 . Loc. ? 430 



3. Polybasite. 9 Ag 2 S, Sb 2 S 3 . Loc? 430 



4. Livingstonite. HgS, 2 Sb 2 S 3 . Taseo... 430 



5. Nagyagite. Au 2 Pb u Sb 3 Te;S 17 . Nagyag 485 



6. Kilbrickenite. 6 PbS, Sb 2 S 3 . Kilbricken 430 



7. Tetrahedrite. 4 Cu 2 S, Sb 2 S 3 . Botes 460 



8. „ „ Westerwald 550 



9. ; , „ Kapnik 530 



10. „ ., Pribram 590 



As stated in the first paper, antimony may sublime as the 

 tetroxide Sb 2 4 or as antimonious oxide Sb 4 6 . The former 

 sublimate is insoluble in cold HC1, the latter is instantly 

 soluble. The earlier experiments seemed to show that the 

 sublimate Sb 4 6 appeared at a lower temperature than Sb 2 4 

 and, hence, was that which generally marked the beginning 



at OO 



and lowest temperature of decomposition. Repeated and 

 careful observations have, however, failed to substantiate 

 this point. Comparison of very many results showed that 

 in successive experiments on the same powder small traces 

 of either oxide might first appear or both appear together. 



A mixture of galena and bismuth ground together in the 

 agate mortar and in the proportions required to represent 

 the composition of zinkenite (PbS, Sb 2 y 3 ), behaved in all 

 respects identical with the mineral zinkenite. Similarly 

 argentite and stibnite mixed to represent the composition of 

 miargyrite (Ag 2 S, Sb 2 S 3 ) showed no difference in behaviour 

 from the latter mineral. 



It will be seen that the results of Table I. agree with those 

 already published. 



Arsenic. 



The subdivision of the arsenic-bearing minerals into three 

 groups according to the temperature at which the arsenic is 

 yielded, as suggested in the first paper, is supported by the 

 more recent experiments. 



