a eee ee te eae 
J. M. Ordway on Waterglass. 29 
quently made, the spirit was purified by agitating it with caustic 
soda and redistilling. 
In examining the various precipitates obtained, extreme accu- 
racy would have involved an unwarranted waste of time; an 
there being scores of analyses to make, it was necessary to adopt 
modes which should be expeditious and without pretending to 
give figures absolutely exact, might still afford close approxima- 
tions to the truth, The alkali was generally determined by sat- 
uration with a standard sulphuric acid. The neutralized liquor 
being then dried down in an oven, the silica was washed, ignited 
and weighed. For a partial control, in most instances, the whole 
amount of solid matter was ascertained by dissolving some of 
the silicate in a little water, adding freshly ignited sulphate of 
lime, and drying the coagulated mass by a heat gradually raised 
to dull redness. This method of expelling the water is, how- 
ever, inapplicable when the silicate is excessively alkaline, as in 
ch cases carbonic acid is absorbed from the hot gases of the 
flame rising round the crucible. 
0 facilitate comparison, the respective amounts of acid and 
base are expressed in equivalents instead of unmeaning per- 
centages, 
Sesquisilicate of Potash,—with Alcohol of sp. gr. 0°842. 
1.—100 parts by weight, of a liquid containing 48 per cent of Ky Sizs0,— 
with 38 parts by weight, of alcohol,—gave 81:25 parts of a liquid pre- 
cipitate differing little from the original solution. 7 
2.—100 pts, of a 25 p. c. solution,—with 41 of alcohol,—gave 448 pts. 
of a liquid precipitate containing 49 p.c. of Kio Sires. wet 
-—100 pts. of a 17:3 p.c. solution,—with 40 of alcohol,—gave 23-2 pts. 
of a liquid precipitate containing 49°6 p.¢. of Kaioo Sines. : 
4.—100 pts. of a 9°3 p.c. solution,—with 39 of alcohol,—gave 42 pts. 
of a solid precipitate not entirely soluble in boiling water, and contain- 
tng, besides alumina and oxyd of iron, 39 p. ¢. of Kioo Sinss- ei 
5,@.—100 pts, of a 4:8 p.c. solution,—with 40 of alcohol,—gave 0°9 pts. 
of an insoluble, pulverulent precipitate containing some alumina and 
oxyd of iron and 70 p.c i00 Sizss. ; as 
5, .—The supernatant liquor of @,—with a further portion of aleohol,— 
gave 3°6 pts. of a hard, coherent precipitate soluble in water and con- 
taining 54 p.c. of Kio Sisss. 
Bisilicate of Potash,—with Alcohol of sp. gr. 0°824. 
6, a.—100 pts. of a crude solution containing 10 p. c. of Kio Sirss,—with 
10 of alcohol,—_gave 2°13 pts. of a hard precipitate which was not 
3 
