180 J. M. Ordway on Waterglass. 
predicable of the reactions is that mixtures containing as many 
equivalents of alkali as the sum of the equivalents of SnO, and 
iO,, are likely to undergo little or no change at the common 
temperature of the air; but when the mixture contains less 
alkali, gelatinization will occur in a few hours or days ; and the 
curd will be greater in amount according as the strength of the 
liquors put together is greater, and as the total proportion of 
The segregated matter retains the alkali with no little force, 
for when the air-dried precipitate is washed with water 4 part 
indeed of the alkali is removed, but the greater portion remains 
obstinately in combination. 
19. Some of the cake of 13 a, was reduced to powder and kept over 
lumps of caustic soda eighteen days. The dry powder was well washed 
It is difficult to ascertain whether the fresh undried cake may 
go dissociation in any greater degree; for if we attempt 
to wash it, though a part settles, the supernatant liquor remains 
milky a very long time, and the suspended matter cannot be 
separated by filtration, as it readily goes through the pores of 
the paper. : 
After seeing how a deficiency of alkali facilitates the coagula- 
tion of a mixture-of stannate and silicate, we should hardly ex 
pect to find metastannates so slow in yeaa any effect on 
waterglass. But metastannates are evidently not mere poly acid 
stannates, and a higher degree of compatibility is the less sur 
prising when we consider the many points of resemblance be- 
tween metastannate of potash and waterglass itself. Both are 
uncrystallizable and dry to tran 
ent gum-like masses, indefi- | 
