190 F. W. Clarh — Constitution of the Zeolites. 



Chabazite— Ganges from Al.X.Ca, . 18H 2 0, to Al 3 X 3 Xa 3 . 

 9H.,0. with Si0 4 : Si 3 ; :': 1 : 1, giving apparently inetasilicate 

 ratios. On fusion, according to Doelter, gives silica and 

 anorthite. In the lime salt four molecules of water and in 

 the soda salt two molecules are to be considered as constitu- 

 tional ; giving the ultimate formulae 



Al 4 X 6 Ca s H 4 (AlH 2 o ) 2 . 14H„0, 

 Al 2 X 3 Xa 3 H 2 (AlH 2 dJ.7H 2 



Gmelinite. — Al s X 3 Xa 3 . 9H 2 0, or like the non-calcic chaba- 

 zite ; but with Si0 4 : Si 3 8 : : 1 : 2. Two molecules of water 

 are probably constitutional. 



Hydronephelite. — Al 3 (Si0 4 ) 3 Xa s H . 3H 2 0. Clearly a deriva- 

 tive of nepheline. 



Offretite. — The analysis by Gonnard agrees sharply with the 

 formula — 



2Al s (Si 3 8 ) 3 K 2 . 8H a O + Al,(Si0 4 ),CaH . 8H 2 0. 



So much for the first group of zeolites, which is character- 

 ized by the perfectly uniform ratio of Al : X = 6 : 6 or 3 : 3, 

 accordingly as bivalent or univalent bases predominate among 

 the remaining metallic components. The second group is 

 similarly defined by the ratio Al : X = 4 : 6 or 2:3; the 

 water being the chief variable. In detail, the members of 

 this group are as follows : 



Foresite.— Al 4 (SiO 4 ) 6 CaH 10 . H 2 0. 



Scolecite.— Al 4 (Si0 4 ) 6 Ca 2 H 8 . 2H 2 0. According to Doelter, 

 yields anorthite on fusion. Converted into natrolite by the 

 prolonged action of soda solutions, according to Lemberg. 

 Loses about -J of its water at 300°, regaining the same in moist 

 air. 



Laumontite. — Al 4 X 6 Ca 2 H 6 . 4H a O. Si0 4 : Si 3 8 = 5:1. 

 Yields anorthite and a pyroxenic mineral on fusion. Loses 

 about | its water at 300°. * 



Eeulandite.— Al 4 X 6 Ca 2 H 8 . 6II 2 0, with Si0 4 : Si 3 8 = 1:1. 

 According to Doelter, yields a " lime augite " on fusion, with 

 silica. This observation may best agree with the metasilicate 

 formula A] s Ca(SiO s ) 6 H 4 . 3H 2 0, both formulae being empiri- 

 cally identical, and both in accord with the behavior of 

 heulandite upon dehydration. 



£ rev: sterile.— Like heulandite, but with barium and stron- 

 tium replacing lime. 



Epistilhite. — Isomeric with heulandite, but with the water 

 apparently more firmly combined. Perhaps a part of the Al 

 is replaced by AlH„0 o + H 2 . 



#*«&.— Al 4 X 6 Ca 2 H 8 . SH 2 0, with Si0 4 : Si 3 8 = 1:1. On 

 fusion, behaves like heulandite, but sometimes yields anorthite. 

 The variations in composition are probably due to variations in 

 the ratio between the ortho- and trisilicate groups. 



