J. M. Ordway on Waterglass. 195 
boiled an hour with 80 c. ¢. of water. A second boiling was contin- 
ued one hour. The ignited residue made only 0°93 p.c. 
4, b.—10 g. of the same product were boiled one hour with 1000 c. « 
of water. After another boiliug the dry residue amounted to 1°73 p. c. 
It seems then that, in boiling anhydrous waterglass the amount 
of matter left undissolved depends, in a great measure, on the 
' quantity of water used. In other words, very siliceous water- 
glass is not integrally soluble in mere water, but dissolves with- 
out any considerable decomposition in a strong solution of the 
Silicate itself. When the least practicable proportion of water 
is taken, the light flocculent deposits actually obtained are made 
up chiefly of earthy and metallic silicates; and it may be fair] 
inferred that in such cases an absolute y pure silicate of ublel 
or soda would give no remainder except the very little produced 
by the first contact of pure water with the outer surface. 
the sediment left after the action of a large quantity of water is 
tse and scaly, and under the microscope appears to consist 
of purely siliceous filmy skeletons of the original particles of the 
glass; and there would doubtless be such a residue even though 
the silicate were completely free from foreign matter. The 
greater the proportion of alkali, the less decomposable is fused 
Waterglass; and we may safely say that pure products, a little 
More alkaline than the sesquisilicate, would dissolve without 
remainder in any quantity of water however great. 
Recent applications of Waterglass, 
A mere allusion was made in Part IIL to the admixture of 
ith 
seemed 
0 Use anything so excessively alkaline as hquor silicum,—which 
8 what the oldest propositions all direct,—is taking a long stride 
Stage of the soap manufacture, involves a troublesome change in 
