July, 3 957
VOLTAMMETRY AT CONTROLLED CURRENT WITH DROPPING MERCURY ELECTRODE 965
TABLE I11 SOLUBILITY OF SILICA IN ALKALINESOLUTIONS POH
(Monomer) X 108, moles/l.
log KI,
3.72 3.40 3.15 2.96
8.83 18.3 35.0 60.0
5.39 5.06 4.80 4.70
A similar analysis of the turbidity and pH data in the present study gave the results shown in Table IV. TABLE IV PH
9.9 10.4 10.5 10.7 12.1
EQUILIBRIA I N CSiOH (1
ALKALINE SOLUTIONS
- X)
23.8 34.0 31.2 21.2 92.8
CD
(5)
76.2 66.0 68.2 78.8 7.2
log KD
7.6 6.9 6.6 6.0 5.1
The product of depolymerization of the silica should be a mixture of low molecular weight silicic acids. The turbidity r and the 90" readings r are proportional to the quantity N V 2 where N is the number of particles per cc. and V is the volume of each particle. If the volume fraction N V is essentially constant during depolymerization then OD V , which is the case in aggregation reactions. The dissymmetry measurements could not be used to evaluate V because of the small size (
