COLONEL P. TOEKE’S EESEAECHES ON SILICA. 
535 
was weighed when cold, and again heated for five minutes until the last two weighings 
agreed wdthin a few hundredths of a grain. The loss was then estimated as carbonic 
acid. The equivalent of the silicic acid is then readily obtained by the following pro- 
portions, 22 being the equivalent of carbonic acid on the hydrogen scale: — 
22 X weight of silica used 
^ weight of carbonic acid expelled 
Experiments with Carbonate of Potash. 
Quantities used. 
r 
Carbonate of Potash. 
1 
Silica. 
Loss = Carbonic 
Equivalents of 
No. 
grs. 
grs. 
Acid. 
Silica deduced. 
I. 
52 
10-67 
7-5 
31-3 
II. 
61-3 
13-45 
9-62 
30-06 
III. 
30-7 
10-07 
7-04 
31-4 
IV. 
47-4 
10-10 
7-26 
30-06 
Mean . . . 
. 30-07 
This result 
agrees very nearly with 
that of Rose, 
and also with 
the formula SiO,^, 
which, if calculated from the percentage composition of silicic acid 
as stated by Beeze- 
LIUS, would give 30'75. If from that assigned to it by Pelouze, it would be 30’22. 
Experiments with Carbonate 
of Soda. 
Carbonate of Soda. 
Silica. 
Loss= Carbonic 
’ Equivalent of 
No. 
grs. 
gi’s- 
Acid. 
Silica deduced. 
I. 
58-16 
13-08 
13-7 
21 
II. 
59-12 
12-17 
12-15 
22 
III. 
60-68 
13-86 
13-94 
21-8 
IV. 
53-04 
16-45 
15-2 
23-7 
V. 
34-84 
9-06 
11-3 
17-6 
VI. 
55-78 
15-85 
15-89 
21-2 
VII. 
59-12 
16-1 
16-34 
21-7 
Mean . . 
. . 21-3 
Here then 
I obtained a very difierent result from that with carbonate of potash, 
agreeing more nearly with half the number represented by the formula 
oiO,, or — 
As M. Jacquelain had stated that under certain circumstances carbonate of soda lost 
part of its carbonic acid by fusion*, I made the following experiments to ascertain whe- 
ther, in my method of experimenting, the loss I had observed could be attributed to the 
action of heat alone. A portion of the carbonate of soda used in the last-mentioned 
experiments was fused for three or four minutes, it weighed=78‘5 grs. 
♦ Ann. de Chim. &c. 3 ser. xxxii. 195. 
4 A 2 
