ON BASIC SUBSTITUTIONS IN THE ZEOLITES 263 



From formula' of this character, structures of many types are 

 derivable, and some of them may contain chlorine. The sodium 

 stilbite, prepared by Mr. McNeil, may be represented thus : 



4AI— SiaOs^Al + A\—Si,0^='Sai + Al— SiO^sNaj 

 \si30s=Al ^SijOg^Al \siOt=Al 



the last molecule having been formed by loss of silica from the 

 original trisilicate molecule. This set of symbols corresponds 

 to the percentage composition given below, as contrasted with 

 the average of McNeil's two anal3'Ses. 



Calculated. Found. 



SiO,, 64.88 65.03 



AlO., 20.05 20.06 



CaO ) 91 



XaaO \ 13-72 12.60 



CI 1.74 1-71 



100.39 100.31 



Less O 39 -S^ 



100.00 99-93 

 The sodium chabazite agrees well with a mi.xture of the sec- 

 ond and third molecules in the expression given above, in the 



ratio of 5 : 3 ; thus : 



5Al,Na3(Si30,).Cl ; 



3Ai;Na3(SiO,),Cl ; 

 which compares as follows : 



Calculated. Found. 



SiOj 54-90 54-77 



AljOs 20.67 20.36 



CaO } 1.52 



NajO ) 18.S5 17.42 



CI 7- 10 6.92 



H^O -28 



101.52 101.27 



Less O 1-52 1-56 



100.00 99-71 



In silver chabazite, which was prepared by the action of silver 

 nitrate upon the mineral, NO3 appears in place of CI, and we 



have 



3AlAg3(Si303),N03; 



iAlAg3(SiO,),N03; 



