J. M. Ordway on Waterglass. 193 
12. When a silicate of one alkali is precipitated by a salt of 
the other, both bases enter into the composition of the solid pro- 
duct, and the relative proportion of potash and soda therein, is 
be nearly the same as in the average of the liquors mixed. 
The method here adopted, for determining the net composition 
of an unwashed precipitate, might perhaps be found advanta- 
geous in many other cases in which pure water is likely to alter 
a deposited product,—-and such cases are probably of more com- 
mon occurrence than has been heretofore suspected. Of course 
When a mother-liquor would of itself contain no peculiar sub- 
stance capable of showing, by the comparative quantity of it 
found in the drained precipitate, the amount of contaminating 
liquor, it would generally be easy to add some special indicator. 
Decomposition of Waterglass by Water. 
It is a question of no little interest, as well as of some practi- 
cal Importance, whether different solutions made from a given 
4 manufacturer how successful he had been in fluxing a mixture 
Mtended for bisilicate of soda. Some of the uniform product 
Was at first sent for examination to a noted analytical chemist who 
Teported that when 25 grains of the sample, re uced to fine pow- 
In first boiling and 4 oz. in the second,—the “precipitate and 
Insoluble matter,” washed, dried, and burnt, amounted to 13 
®ccount was rather surprising and unsatisfactory, for the vitreous 
i Showed i en made from 
€an materials it could hardly contain any “insoluble glass. 
Pulverizing some of the same well vitrified silicate, I boiled 20 
