Electrokinetic Potentials. Xi. The Effect of Sodium Soaps on the Electric Moment of the Double Layer at an Aqueous-Cellulose Interface

Abstract

1. Electrokinetic studies of aqueous solutions of sodium formate, sodium acetate, sodium propionate, sodium butyrate, sodium caprylate, sodium oleate and sodium oxalate have been conducted at a cellulose interface with the streaming potential technique. 2. It is suggested that in interest of clearness and accuracy the attempt to express electrokinetic data in terms of ``potentials'' be abandoned and that the electric moment of the double layer, which does not require a knowledge of the magnitude of the dielectric constant, be substituted for ζ. 3. It is indicated that after the fourth carbon atom has been added the electric moment of the double layer is essentially a constant. 4. It is noted that there is no correspondence between the ionization constant of the fatty acid from which the soap is derived and its effect on the electrokinetic conditions at the interface. This indicates that hydrolysis and the resulting OH ion plays a minor role. 5. It is pointed out that the electric moment of the double layer in the case of the longer chained soaps is almost independent of the concentration whereas that of the short chained soaps are much more sensitive to increased concentration. 6. The maximum electric moment is found at about 2×10−4 normal. This is true also for a number of salts.

Electrokinetic Properties of Proteins. II. Adsorption of Gliadin at Glass–Liquid Interface as Influenced by Hydrogen-ion Concentration.

“…or µ = 2.65 X 10-4 X ef (6) where e is the value for the dielectric constant used in the original calculations. Although the value for e generally used in calculating the ¿"potential from streaming potential data is probably incorrect, as explained by Bull and Gortner (7), expressions 5 and 6 may be used to convert the data of this and other papers to a comparable basis.…”

The Electrokinetic (Zeta) Potential of Thin Metal Films.

“…The values of the electrokinetic (zeta) potential are calculated according to the expression used by Briggs (1), 4 ]Hks ~Pe (1) where H is the electromotive force set up across the diaphragm, kb is the specific conductivity of the liquid in the diaphragm, the viscosity of the solutions, P the hydrostatic pressure, and e the dielectric constant. Using the proper constants at 25°C., Hk Í (volts) = 97.165 X -y- (2) where H is measured in millivolts, ks in reciprocal ohms, and P in centimeters of mercury. Bull and Gortner (2) suggest, in view of the existing doubt as to the correct value of the dielectric constant which should be used in the formula, that the value of the electric moment of the double layer be used to express the capillary electric conditions at the interface instead of the electrokinetic potential.…”

“…The cell was assembled with thin rubber gaskets to insure against leq-ks, and the whole was clamped tightly together with a specially constructed clamp. 2 Unpublished results of a series of similar experiments in this laboratory confirm the strong adsorption of complex ammonia ions in ammoniacal solution. Figure 1 shows the complete cell and pressure system.…”

“…Silica gel adsorbs these cations very strongly, 1 g. of silica gel adsorbing as much as 0.32 g. (1.692 millimoles) of the silver complex and 0.31 g. (1.10 millimoles) of the nickel complex. 2 After adsorption had reached equilibrium the liquid was drained from the gel, the gel was dried, and finally heated in a current of hydrogen until the complex salt in the gel was reduced and the metal left in a free state on the surface of the gel. The product was a deep black, and microscopic examination of the granule showed no uncovered silica surfaces.…”

The theory of electrokinetic phenomena

“…Bull and Gortner (23) suggest three reasons why the dielectric constant of the double layer would be different from that of the liquid in bulk.…”