12 Prof. J. Joly on the 



obtainable from colloidal bismuth, attending deflagration. 

 It is not volatilized off the glasses and is insoluble in HOI or 

 in solution of KHO. It whitens slowly when heated on 

 the glass. 



The test by chloride of tin is the best for bismuth under 

 the conditions obtaining in these experiments. Put a drop 

 or two of solution of SnCU on the sublimate, followed by a 

 couple of drops of dilute HOI, and work round with a stirring- 

 rod till all is dissolved. Add now a little NH 4 HO solution, 

 or KHO solution, till the first formed white precipitate is 

 dissolved. The ppt. of Bi 2 2 then slowly collects. 



If the sublimate is soluble in KHO sol., it is even more 

 effective to add a little of this and then drop in a few crystals 

 of Sn01 2 ; these only partially dissolve and rapidly blacken, 

 bringing down the black oxide. This black precipitate 

 will be found to whiten in a few hours if left exposed to 

 the air. 



Table V. 



white heat. 



2. Bismuthenite. Bi 2 S ;! . Sehneeberg. Volatile subl. at fi00°-600° with 



deflagration ; subl. of Bi.,0 3 at white heat. 



3. Gralenobismutite. PbS, Bi 2 ^ 3 . Nordmarken. Tr. of Bi 2 3 with defla- 



gration at 5ti0° ; and at high temperature. 



4. Cosalitevar. Bjelkite. 2PbS, Bi 2 S 3 . Bjelke Mine. Tr. of Bi 2 3 with 



deflagration at 720° ; and at white heat. 



5. Lillianite. 3 PbS, Bi 2 S 3 . Lillian Mine, Leadville. The high temp. subl. 



of Bi 2 3 only observed. 



6. Aikinite. 3(Pb . Cu 2 )S, Bi,S-,. Loc. ?. Tr. of Bi 2 3 with deflag. at 



510° ; Tr. of vol. white subl. at 600° ; Bi 2 3 at 

 high temperature. 



7. „ BeresolT, Siberia. Tr. of Bi 2 3 at 620° with deflag. and at 



high temperature. 



8. ,. Loc? Tr. of Bi.,0 3 with deflag. at 670°; Tr. of vol. white 



subl. at 820°. Bi 2 3 at high temp. 



9. Emplectite. Cu S, Bi 2 S 3 . Schwarzenberg. Tr. of Bi.,0 3 at 600° with 



fleflag. ; and at 1200°. 



10. Tetradymite. Bi 2 Te 3 . Schemnitz. Bi 2 3 at white heat. 



11. Alloclasite. Co(As. Bi)S. Loc. ? Bi 2 3 at 1350° with red streaks. 



In the case of the sulphobismuthites the high temperature 

 at which the sublimate of the oxide appears in bulk does not 

 define the decomposition point of the mineral, but only that 

 at which the oxide itself becomes volatile. The oxide is, in 

 fact, formed at some lower temperature, collecting upon the 

 hob while other volatile constituents pass off, and remaining 



