338 J. M. Ordway on Waterglass. 
stirring, till the liquor acquires a sufficient strength as shown by 
the hydrometer. If the solution is dipped out hot, either the 
kettle must be immediately filled again with hot water, or the 
glass also must be taken out and held back till the water becomes 
hot, otherwise the silicate is apt to stick together and adhere 
most obstinately to the bottom of the kettle. 
en a waterglass contains a greater proportion of silica than 
is needed to constitute a bisilicate, its solution is the work of 
many hours. And silicate of soda is somewhat harder to dis- 
solve than a corresponding silicate of potash. -As the relative 
amount of silica is increased, the precise point at which the pro- 
duct ceases to be integrally soluble, has never yet been aseer- 
tained. Fuchs speaks of his original potash glass,—KaSis,—as 
being entirely soluble. A monosilicate is readily taken up by 
water at less than the boiling he 
and if sulphids are present, a part of the iron remains in the 
state of sulphuret, giving a blackish color to the sediment. But 
throws down only a part of it. From me may of eee 
in 
ecidedly p ' 
* Kuhlmann mentions a soluble double silicate of potash and manganese. _ om 
une matiére vitreuse d’un violet foncé, qui donne une dissolution brune. Loe 
de cobalt se combine aussi, mais en plus petite quantité, le silicate de po 
—Silicatisation, 8me edition, Paris, 1858, p: 1%. 
