space over 
tightly stopped bottle. But as in cold weather both the forma- 
tion of the r izati be carried 
_ can just as well be rapidly concentrated by heat. 
_ Ammon attempted in vain to crystallize the potash salt and 
to form a double silicate of potash and i os 
All my own efforts to produce crystals of potash silicate have 4 
thus far proved unavailing, though I have exposed very con- 
Centrated solutions, for many days, to the extreme cold of winter. 
Berzelius fixed on SiO, as the constitution of silicic acid, 
Principally on account of an assumed analogy between feldspar 
d son for such 
ak 
lous. Why should w t the plain guidance of the simple — 
_Silicates and selecting feldspar,—a complex, anhydrous combina- 
_ion,—presume on its resemblance to a double sulphate which 
-_* See Part IIL, this J xxxiii, p. 34. In the 18th line from the bottom of 
that page, it pate apegeme to. y filtrate two of alcohol,” 
the 
