steiger.] ACTION OF SILVER NITRATE, ETC., ON SILICATES. 
79 
Water was not determined, but, as will be seen from the summa- 
tion, it is an unimportant constituent of the compound. Evidently 
the anhydrous salt has been formed, but incompletely, for only about 
half the sodium had been replaced. 
The molecular ratios are as follows: 
6PbO, loNa,(), 17A1 2 3 , 100SiO 2 , 
or, combining the monoxide bases, 
L6RO, 17A1 2 3 , 100SiO 2 . 
In this a large excess of siliea appears. 
LEUCITE. 
The specimen of leucite at hand was impure, and more careful work 
was therefore deferred until some future time, when it may be possible 
to prepare an artificial mineral which will be studied in detail. 
One preparation of the impure leucite was made by heating the 
native mineral in a sealed tube with four times its weight of thallous 
nitrate for twenty-four hours at a temperature of 250 J -2 ( ,K) J C. The 
leached residue was dried on the water bath. The analysis of this 
residue follows. 
Molecular 
SiO, . 
Al 2 ;s 
Tl,< ! . 
K,o 
H,() 
H 2 CM 
100.0 
26. 7 
16.8 
7.5 
1.8 
Combining potassium with thallium, the analysis gives the fol- 
lowing: 
24(T1K) 2 0, 27 A1 2 :! , 100SiO 2 , 2H 2 0. 
This indicates that the same molecule has been formed as in the 
;ase of analcite. 
THOMSONITE. 
The thomsonite used was well crystallized material from Table 
Mountain, Colorado. Only one derivative of this mineral was made. 
(The thomsonite was heated in a sealed tube with four times its weight 
|f dry silver nitrate, 20 hours, at 250 -21H) C. The residue was dried 
It about 40° C. Its composition is given on the page following. 
