COLONEL P. YOEKE’S EESEAECHES ON SILICA. 
5.S9 
With Silica and Hydrate of Soda. 
Hydrate of Soda. 
Silica. 
Loss= Water. 
Equivalent of Silica 
No. grs. 
grs. 
deduced. 
I. 100-04 
18-61 
9-18 
18-2 
II. 81-29 
10-07 
5-48 
16-4 
III. 128-24 
15-86 
8-37 
17-0 
Mean . . 
. . 17-2 
In these experiments with the hydrates, it will be observed that the equivalent 
obtained with hydrate of potash is the same as that obtained with the carbonate, but 
that obtained with hydrate of soda approaches more nearly to that afforded by carbonate 
of lithia. 
Reverting now to the experiments with the carbonates, I found that I had, in order to 
secure the reqmsite fusibility in the case of the carbonate of lithia, used a greater pro- 
portion of that salt to the sOicic acid than with the other two carbonates, so that con- 
sidering the ratio of the oxygen in the base to that in the silicic acid in the case of the 
lithia experiments, it was nearly as 2:1, whilst in the other two carbonates the oxygen 
was equal in the base and in the silicic acid. To ascertain if this would in any way 
explain the results I had obtained, I made two experiments with carbonate of potash, 
in w’hich the oxygen, considered as belonging to the oxide of potassium, was double that 
contained in the silica, and obtained for the equivalent the number 29 very nearly. 
Operating in a similar manner with carbonate of soda, the mean of two experiments 
gave 19'5. 
Both the numbers thus obtained are slightly smaller than those given in the former 
experiments, but I do not think they should materially affect any inference to be drawn 
from them ; and I may remark here, that, though I am of opinion that generally the 
(quantity of carbonic acid expelled by an anhydrous acid from the alkaline carbonates in 
fusion may be very valuable for determining between two different formulas for such 
acid, I do not think that the method is capable of determining with precision the 
equivalent w'eight of such an acid, as I have satisfied myself in the course of these expe- 
riments, that when the heat is long-continued, minute, but appreciable quantities of 
the alkali are volatilized. 
On Crystallized Hydrate of Silicate of Soda. 
A sihcate of soda was formed by taking one equivalent of carbonate of soda, or 
54 parts, and one eqmvalent of silica as given by the results of the experiments before 
detailed, or 23 parts, and fusing them together, the quantity of carbonic acid present 
would be 22 ; the quantity actually expelled was 20, so that 2 parts =5 of carbonate of 
soda had remained in the fused mass. This substance appeared crystallized throughout, 
and to be made up of spheroidal masses of prismatic crystals radiating from a centre. 
This kind of crystallization invariably followed on fusing together the two substances in 
