Paraffin-chain salts

G. S. Hartley, A.queous Solutions of Paraffin-Chain Salts Hermann Cie, Paris, 1936, p. 45. 

Hartley, G.S. "Aqueous Solutions of Paraffin Chain Salts" Hermann et Cie Paris, 1936. 

Hartley GS. Aqueous solutions of paraffin-chain salts a study in micelle formation. Paris Hermann Cie 1936. 

Hartley GS (1936) Aqueous Solution of Paraffin Chain Salts, A Study of Micelle Formation. Herman and Co, Paris... 

Synonyms for surfactants include amphi-philes, surface-active agents, tensides, or, in the very old literature, paraffin-chain salts. 

Hartley, G. S. (1936). Aqueous Solutions of Paraffin Chain Salts (Hermann and Cie, Paris). 

Flochart, B.D. (1961) The effect of temperature on the critical micelle concentration of some paraffin-chain salts. /. Colloid Sci., 16, 484-92. 

Paraffin-chain salts, similar in general constitution to the soaps but containing a strongly dissociated end group such as a sulphonic acid or a quaternary ammonium atom, are not subject to hydrolysis, and might be expected to behave in a simpler manner. The surface-tension measurements of Adam and Shute,1 R. C. Brown,2 and Lottermoser and others8 indicate, however, a curious, very slow attainment of the final surface tension in solutions so dilute that there are few, if any, ionic micelles present in the interior. The tension may take several days to reach the final value and when the final tension is reached it appears to be independent of the concentration, at least for solutions over 0-003 per cent., i.e. of the order N/10,000. The amount of this final tension depends somewhat on the nature of the end group it is usually about 30 dynes per cm. 

Naturally, other paraffin-chain salts with one water-soluble end group also form fairly stable films and foams. Proteins, saponins, gamboge, resinates are also capable of forming stable foams the two last named were found by Perrin to form stratified films, just like the stratified soap films. 

The quantity in the ordinary theory of electrolytes which corresponds to the potential in electrokinetics, is the potential due to an ion, at a distance from its centre equal to its radius, i.e. half the distance of closest approach of two ions. In the case of moderately complex charged particles such as the ionic micelle of paraffin chain salts, soaps, etc., the potential is the potential in the water just outside the micelle with its adherent gegenions , the small ions of opposite sign which, according to G. S. Hartley, adhere to the micelle and very considerably affect its motion in an electric field.1... 

McBain1 has drawn attention to the existence of a number of cases in which strongly surface active substances first lower the tension of water considerably, but as the concentration increases further, the surface tension either becomes nearly constant or shows a slight increase. The cases for which the evidence is most conclusive are aqueous solutions of soaps or other paraffin chain salts and of some dyestuffs. The minimum surface tension often occurs in quite dilute solution, e.g. with dodecyl sodium sulphate2 it is about 0 006 N the exact concentration of the minimum, however, depends on the purity of the water used as solvent. 

Small concentrations of di- and trivalent ions do, however, produce very low interfacial tensions with the simple paraffin chain salts l and if substances such as cholesterol, which form complexes with the paraffin chain ions, are present in the oil, again very low tensions are possible. There is little doubt that either the polyvalent ion, or the other molecule of the complex, binds the paraffin chain ions together laterally in the interfacial film, so that more ions crowd into it for equal concentration of paraffin chain ion in the water, with a lower tension as a consequence of the greater crowding. 

Indicators, if their ionizable groups are present almost exclusively at the surface, and if the colour and optical density of both forms are unaffected by this adsorption, may be used for determining the pH at the surface. Using the triethanolamine salt of cetane sulphonic acid, the pu at the surface of the micelles was found colorimetrically by diphenylazo-o-nitrophenol. p-nitrophenol was employed to find the pu in the solution curiously it was more difficult to find a suitable indicator for the bulk than for the surface pH, since almost all indicators are more or less adsorbed at the surface of these paraffin chain salts. Preliminary experi-... 

Hartley, G. S., Collie, B., and Samis, C. S., Trans Farad. Soc. (1936), 32, 795-815, "Transport Numbers of Paraffin-Chain Salts in Aqueous Solution."... 

Electrolytes showing clustering properties are typified by paraffin chain salts where there is a long paraffin-like chain with a cationic group at the end, as in a quaternary ammonium group ... 

Fig. 7. Possibilities of association of paraffin chain salts according to Hartley.

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