131 Brown — Composition of the Selensulphur from Ilaivaii. 



the air bath was opened to remove the samples. The amounts 

 lost were, however, too minute to cause appreciable difference 

 in the determinations. The lava discarded as showing practi- 

 cally no selensulphur must have contained some as an invisible 

 impregnation, for an analysis of this material showed selenium, 

 0*07 per cent, and sulphur, 3*32 per cent. 



The composition of the hand picked sample is given in col- 

 umn 1, the same after deducting the material other than 

 selenium and sulphur recalculated to 100 per cent in column 2, 

 and the ratio of selenium to sulphur in column 3. 



l 2 3 



Loss at 103° (moisture)... 3-16$ 



Sulphur _ 12-44 94-82$ 2"956 45-5 



Selenium 0-68 5 ; 18 -065 1 



Remainder (lava).. (83-'72) 



100-00 100-00 

 Specific gravity 2'378. 



Alloys of sulphur and selenium containing from 35 to 

 66 per cent of the latter have been described,* but the min- 

 eral selensulphur is here found to contain such a small amount 

 of selenium that it can hardly be considered more than a 

 variety of the main substance, sulphur. It is therefore sug- 

 gested that " seleniferous sulphur" would be a more appropri- 

 ate term than selensulphur to apply to this mineral. 



& 



Bueknell University, Lewisburg, Pa. 



* Browning, Introduction to the Rarer Elements, 2d ed., p. 145. 



