Cadmium, and Mercury. 



349 



The effect of solvents on the inversion point of ZnS. 



When wurtzite is heated in a medium of molten chloride of 

 sodium it changes to sphalerite much more rapidly than when 

 heated in vacuo or in an atmosphere of hydrogen sulphide. 

 Not only did the wurtzite change in the solid state, but new 

 dodecahedrons of the refractivity 2-37 were formed. As the 



Fig. 3. 



2550 

 2530 

 2510 



| 2490 



o 



I 2470 



'5 



ft 2450 



to 



2430 

 2410 

 2390 

 2370 













































































































































































































































































































































































O 





y 









































































































































n 

















































































































































/' 















































A 





















































~~~- 



--, 























































~~- 

























































-- 

























































*■ - 



* 























































-- 



,. 























































*■'- 























































- 



-- 













10 15 



Percentage of iron. 



20 



Fig. 3. Influence of iron on the specific volume of sphalerite. 



surface of the salt was left open to the air a little zinc oxide of 

 lower refractive index than wurtzite was detected by the 

 microscope. The aqueous solution of the sodium chloride 

 gave strong tests for zinc and sulphate. This indicates the 

 reaction 2NaCl + ZnS = Zn01 2 + Na 2 S. The reversion of the 

 reaction in the colder parts of the charge may have caused the 

 deposition of the crystals which are the stable form at that 

 temperature. In a platinum tube protected from the air by a 

 slow stream of carbon dioxide, wurtzite was almost completely 

 changed to sphalerite in 30 hours and excellent small dodeca- 

 hedrons were obtained. Pure amorphous zinc sulphide in 46 



