PLATK rr. 





^^/ ^^J 





5>\c::sa^, 



Fig. 4. — Liquid Cjivstai^s of Ammonium Olf^ai 



Fig. 8. — Modkl of Akrangembnt op Zinc Atoms (shaded) and^ 

 Sulphur Atoms (light) in Zinc Blende. 



