On Colloidal Electrolytes Attempt to Account for the Variation of Osmotic Pressure of Polyacrylic Acid witfi its Progressive Neutralisation by NaOH and to Find its Dissociation constant
| Main Author: | B. N. GHOSH |
|---|---|
| Format: | Article Journal |
| Bahasa: | eng |
| Terbitan: |
, 1972
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/6451618 |
Daftar Isi:
- Department of Chemistry, Calcutta University, Calcutta -9 (Received 25 March 1972) From a consideration of the equilibrium that exists between the counter ions adsorbed in the fixed Stern-Mukherjee layer and those present in the diffuse part of the electrical double layer of the particles of a polyacrylic acid sol the following equation has been deduced connecting the activity, as, of the counter inns in the diffuse layer with the concentration of the N+a ions added in the form of NaOH as=\(K_3f\over K_4Sxd\) . \(a_k \over K_o +C_k\) The significance of the terms in the equation has been explained in the paper. It has been pointed out that the activity of the counter ions in the diffuse double layer is manifested only when the particles of the PAA sol with their double layers come in contact with the osmometer membrane. Therefore, if θ be the fraction per unit area of the osmometer with which the double layers are in contact, then Bas should represent the activity of the counter ions at the membrane per unit area and hence the osmotic pressure p is given by the equation P = RT(\(\theta\)as) = TR\(\theta\) \(K_3f\over{S{x}dK}\) ∙ \(a_k\over{K_o}+c_k\) For a given value of \(\theta\) , RT\(\theta\)K3f/K4S\({x}\)d is constant and hence the aforesaid equation may be written as : P=K\(a_k\over{k_o}+C_k\) The equation has been found to agree well with the data recorded by Kern on the mea surement of osmotic pressure of some PAA sole when they are being neutralised by NaOH. The following equation connecting the "surface dissociation constant" Ks with the observed H+ ion activity Hc has been deduced : Hc =\(\theta\)Ks\((1-a)^n\over(a)^n\) Using this equatffion` the "surface dissociation constant" Ks of PAA has been calculated and found to be 1.1 x 10-5 or Pks= 4.95.