194 J. M. Ordway on Waterglass. 
grams in about 150 c.c. of water for 30 minutes and obtained 
only 3:3 p.c. of residue. In view of so great a discrepancy, no 
one would suppose both determinations to have been correctly 
made. But tinding by another trial that my own result was 
certainly not below the truth, I made the following experiments 
o ascertain whether the apparent error in the other case was the 
fault of the manipulator or of his metho 
1, a.—25 grams of the finely powdered glass were boiled briskly for one 
hour, in a copper vessel, with 100 c. c. of water,—a little water being 
i sett 
weighed 1:2535 g., making 6°27 p.c. 
1, c—15 g. of the sample were boiled for two hours with 1500 c.¢. of 
from water, made 9°24 p. c. 
: qpenfret solution contained NaSigo; the second NaSi,,¢; the third, 
Na ip-4. 
2, b.—80 g. of the same glass were boiled four hours with 1600 ¢. & 
of water. A second boiling lasted one hour, and a third was kept up 
three hours. The ignited residue amounted to 21 p.c. 
2, c.—16 g. of the same powder were boiled four hours with 1600 ¢. ¢, of 
water, and again four hours with 1600 ¢. c. of water. The ignited 
residue amounted to 32 p. c. 
2, d.—8 g. of the same product were boiled four hours with 8 litres of 
water in a kettle heated by steam,—the carbonic acid of gas flame 
being thereby avoided. The sediment was boiled again four hours. 
The ignited residue occupied one third more space than the original 
silicate. It amounted to 34°5 p. c. 
This dehydrated matter contained nearly 97 p.c. of silica; that of % 
96 p.c.; that of b, 94 p.c.; that of a, 86°5 p. ¢. eee por 
8, a.—16 g. of a very pure and perfectly vitrified silicate, —NaSij.7,— 
German manufacture, were boiled one hour with 80 ¢. c. of water. 
The residue, after being boiled again, washed, and ignited, amounted 1 
0°44 p.c. : 4 
3, b.—15 g. after two boilings, with 1500 c. c. of water each time, left 8 
p.c. of dry matter containing 94 p. c. of silica. ; ; 
4, a.—20 g. of a remarkably nice commercial soda silicate, NaSiy.s4, Wel? 
