Clarke.] 
NORMAL ZEOLITES. 
43 
From these, which are empirically identical, we get the subjoined 
comparison between theory and the analysis by Damour :* 
Found. 
Calculated. 
Si0 2 
46.12 
16.81 
4.79 
5.09 
27.02 
47.46 
16.14 
4.43 
4.91 
27.06 
AL0 3 
CaO 
NaO 
H,0 
15H 2 0— 
99.83 
100. 00 
21.36 
According to Jannasch,t faujasite loses 10.88 per cent of water at 
105°-110°. At 150° it loses 16.83, about 12 molecules, which is regained 
in moist air. Between 250° and 260° it loses 22.67 per cent, and the 
remainder of the water is expelled upon ignition. Of the two formulae 
given, the one corresponding to the leucite-analcite type is preferable, 
for it represents the morphological analogy between the species. 
Furthermore, faujasite on treatment with hydrochloric acid is decom- 
posed, but does not gelatinize, a fact which may indicate a predomi- 
nance of trisilicate over orthosilicate groups. This datum, however, is 
of questionable significance. 
One more zeolite, the little-known species offretite, remains to be 
considered in this connection. This may be represented as a mixture of 
two molecules, 
/Si 3 8 =K 2 H ,SK) 4 =CaH 
Al— Si 3 8 =Al. 8H 2 0, and Al— Si0 4 HAI. 8H 2 0, 
Al \si0 4 =Al 
X Si 3 
in the ratio of 2 :1. This gives, in comparison with Gonnard's analysis, 
the following composition : 
Found, t 
Calculated. 
Si0 2 
52.47 
19.06 
2.43 
7.72 
18.90 
52.02 
18.95 
2.30 
7.77 
18.96 
ALO3 
CaO 
K 2 
H 2 
100. 58 
100. 00 
This species is evidently a derivative of orthoclase and anorthite, 
and the calcium term in the foregoing formula may evidently be writ- 
ten on the anorthite type, namely, as Al 6 (Si0 4 ) (J Ca 2 H 2 .16H 2 0. The 
* Dana's System, 6th ed., p. 598. 
tNeues Jahrb., 1887, II, p. 24. 
t Dana's System, 6th ed., p. 1043. 
