Action of Electrolytes on Lyophobic Sols
| Main Authors: | S. GHOSH, S. S. RATHI |
|---|---|
| Format: | Article Journal |
| Bahasa: | eng |
| Terbitan: |
, 1982
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/6361092 |
Daftar Isi:
- Department of Post graduate Studies and Research in Chemistry, Jabalpur University, Jabalpur (M. P.) Dhar and coworkers showed that besides the valency of the oppositely charged ion of the electrolyte its precipitation value for a lyophobic sot is defined by the specific adsorption of similarly and oppositely charged ions by the colloid particles, dilution of the sol, and also on the mode of addition of electrolytes, in parts or all at once. The precipitation value is affected by the time 't' the electrolyte is in contact with the sol. It is also affected by temperature. Ghosh and coworkers showed the applicability of the rate equation for a chemical reaction to coagulation process, so that \(\frac{\mathrm 1}{\mathrm t}\)= kpz exp- (-E/RT), where \(\frac{\mathrm 1}{\mathrm t}\) is proportional to the rate of coagulation, p is the probability of formation of a stable aggregate, E the energy of activation, and z is number of collisions in unit time. In this paper further experimental support has been obtained by the study of gelation as well as coagulation of ferric and aluminium phosphate sols effected by electrolytes at different temperatures. It has been also shown that log kpz =α log C+ß, where C is the concentration of the electrolyte, α and ß are censtants, and therefore log t = α-log C +k1, where k1 is constant provided E does not vary for different concentrations of the electrolyte. This relation of the time of coagulation and concentration of the coagulating electrolyte is very similar to those proposed by several other workers. It is suggested here that p and E define the stability of the sol. E is large if (i) attractive force of the aggregating particle is small and (ii) the electric charge, which repel the particles to come together is large, whereas p increases with the decreasing electric charge on colloid particles effected by an electrolyte. It has been repeatedly observed that where E is large, kpz or p is also large, and such behaviour is so common for chemical reactions. The sols of the phosphates of ferric and aluminium become unstable by adding dioxan, which lowers the dielectric constant of the medium and compresses the double layer, a behaviour similar to the initial condition produced by a coagulating electrolyte. But considerable lowering of energy of activation suggests that dioxan also increases the attractive force of the colloid particles of the two phosphate sols investigated here.