538 
COLONEL P. YOEKE’S EESEAECHES ON SILICA. 
Exjperiments with Carbonate of Potash. 
Carbonate of Potash. 
No. grs. 
1. 46-98 
II. 48-28 
Alumina. 
grs. 
21-2 
21-16 
Loss= Carbonic Acid. Equivalent of Alumina 
deduced. 
9-15 50-9 
9-05 51-4 
Mean .... 51-1 
Carbonate of Soda. 
I. 46-12 
II. 52-21 
With Carbonate of Soda. 
20-03 8-83 
27-18 11-93 
51 
50 
Mean .... 50-5 
The equivalent usually assigned to alumina is 51-4. 
Turning now to experiments made with the view of obtaining the equivalent of silicic 
acid in the weight of some other acid than the carbonic, I made some attempts t\T.th 
chloride of sodium and sulphate of soda, but with these did not succeed; 1 then had 
recourse to the hydrates, and will give the results 1 obtained. But I must premise that 
the difficulties of obtaining accordant quantities are much greater -with these bodies than 
with the carbonates, difficulties which arise from the volatility of the alkalies on the 
one hand, and the tendency to absorb carbonic acid during the experiments on the 
other. 
Of the various methods which I tried, I think that the best and simplest was to fuse 
the alkaline hydrate and weigh it in a deep narrow silver crucible proAided Avith a 
cover, and of large capacity compared with the bulk of materials employed, then to add 
the silica and weigh the two bodies together ; to heat this crucible Avhile much inclined 
A'ery gradually, and finally to repeat the weighings and heatings until the weight 
appeared constant. The last two experiments Avith hydrate of soda were made in this 
manner. 
Experiments with Silica and Hydrate of Potash. Water = 9. 
Hydrate of Potash. 
Silica. 
Loss = Water. 
Equivalent of Silica 
No. grs. 
grs. 
deduced. 
I. 73-27 
18-39 
5-39 
30 
II. 105-39 
19-22 
4-7 
36-7 
III. 96 
16-08 
4-95 
29-2 
IV. 87-44 
6-55 
1-8 
32-7 
V. 70-38 
7-37 
2-39 
27-7 
VI. 74-7 
7-65 
2-59 
26-1 
Mean . . 
. . 30-8 
