Cadmium, and Mercury. 



357 



fibers and felted fibrous structure. Inside of some were nuclei 

 of amorphous material, indicating again that the precipitate 

 was at first amorphous. Crystalline material all wurtzite. 



Exp. 7. Temperature 250°-2-5#H i SO 4 . Both large and 

 small spherules, the last in clustered form and amorphous, the 

 large ones mostly doubly refracting and crystalline wurtzite. 



Exp. 8. Temperature 350°- 5^H 2 S0 4 . Possibly 30 per 

 cent wurtzite, the rest sphalerite. 



Exp. 9. Temperature 350°-10^H 2 SO 4 . Perhaps 80 per 

 cent wurtzite, the rest sphalerite. 



Exp. 10. Temperature 350° - 2'5^ H 2 S0 4 . Most of the prod- 

 uct consisted of small spherules, of which about 30 per cent 

 was amorphous, the rest felted aggregates of wurtzite. 



Exp. 11. Temperature 250° — 1^H 2 S0 4 . Consisted almost 

 wholly of irregular granules, much of it isotropic and having 

 the refractive index of sphalerite. In strong light considerable 

 of it shows double refraction and the index of wurtzite. 



Exp. 12. Temperature 300°-2-5^H 2 SO 4 . All apparently 

 isotropic irregular forms having the index of sphalerite. 



Table VII. 



Influence of temperature and acid concentration on the crystalline form 

 of Zinc sulphide. 









Percentage of H 2 S0 4 







Tem- 















pera- 















ture 



10 



25 



4-0 



5-0 



7-5 



10-0 



350° 



no wurt- 



70$ 

 wurtzite. 



70$ 



30$ 

 wurtzite. 







80$ 

 wurtzite. 





zite ; very 



no 



wurtzite ; 



5$ 



90$ 



100$ 



300° 



little 



amorphous 



sulphide. 



much 



sphalerite 



wurtzite. 

 all 



rest 



amorphous 



sulphide; 



no 

 sphalerite. 



wurtzite. 



all 



wurtzite 



wurtzite. 



250° 



as well as 



wurtzite 





wurtzite 









wurtzite. 



and 



amorphous 



sulphide. 





and 



amorphous 



sulphide. 







The results of these experiments are summarized in Table 

 VII. When all the data are carefully compared, it will be seen 

 that temperature and acid concentration appear to be the two fac- 



Am. Jour. Sci.— Fourth Series, Vol. XXXIV, No. 202.— October, 1912. 

 24 



