192 J. M. Ordway on Waterglass. 
37, a.—100 g. of 25 p.c. NaSig.g, cooled to 6° C. were mixed with 100 g. 
of 25 5 p.c. Na® cooled to 14°. The precipitate hard pressed, and after 
48 hours again hard pressed, weighed 38°8 g., and contained 54 p. c 
gross of NaSi 
a'.—92 g. of the sear heated to 90° C,, gave 1 g. of a curd 
containing 44 p.c. of NaSis. 
b.—100 g. of 25 p. c. NaSigg a 100 g. of 25 p.c. Naf, on being mixed 
at a boiling he A gave 34 g, of a hard pressed, transparent, soluble 
mass conta 58 p. c. gross of NaSiggo 
The mother- “Hqut? cooled fo- 1”. 0, ranuinea perfectly clear. 
38, aa g. of 25 p. c. NaSiog at 2° C. were mixed with 100 g. of 25 
p.¢. NaS. The precipitate contained 8°3 g. of NaSig 3¢. 
a'—137 g. of the mother- Lae heated to 90° C., gave a precipitate in 
which there were 1:56 
6.—100 g. of 25 p.c. NaBing and 100 g. of 25 p. c. NaS were heated to 
the boiling point and et The hard pressed curd weighed 20°6 g» 
and contained 95 Si 
The a -liquor eeakenl clear on cooling. 
These examples, selected from more than a hundred trials, 
serve to Hfitistrate the following points :— 
1. Many neutral potassium and sodium salts cause a precipita 
i in liquid waterglass; but the various salts are very unequ 
recipitating power, the acetates and chlorids being particu 
bas 'y efficient. 
2. The less alkaline the silicate is, the more matter is throw2 
down by a given saline liquid. 
3. The more sch ceielented the solutions are, the more complete 
is the precipitation. 
4, Heat increases the precipitating power of the chlorids, 
siete and nitrates, and diminishes that of the acetates. 
ith strong liquors, an inerease in the quantity of precipi: 
tant ka is not attended by a proportionate increase in t 
amount of coagulum; but a little more of the saline liquid than 
will just prides a disturbance usually suffices to throw down 
the greater part of all that is precipitable. 
6. The deposits have a ae or less tendency to cohere into 
a hard or pasty mass, and can therefore be in a _— measure 
freed from adhering mother-liquor by strong press 
And it may be remarked, in passing, that the solid precipitates af 
obtained from waterglass by means of alcohol, are dep <_ 
extraneous liquor more readily and bl noo by the seal t 
by the slow process of absorption recommen art I wn 
7. When the products, thus forcibly sheared: of foreign mat 
are less siliceous than the oe — are wholly solu gor 
cold water. Exposed to the air a day or two, ina aa 
lace, they lose 20 p. e. or more of their enh and beco 
ry and hard,—the ROPaDEity remaining unimpai aired. 
