Raymond Defay

I. Measurement of dynamic surface tensions of aqueous solutions by the oscillating jet method

Abstract The rate of surface tension lowering of aqueous solutions of ten long-chain alcohols and two dicarboxylic acids has been measured by the oscillating jet method. The surface tensions have been calculated by the Bohr formula. Seven orifices, standardized with water, have been used to determine the variation of surface tension with age for an aqueous solution of heptanol (0.4 g./l). The results obtained, which lie on a single curve, are compared with published values.

III. The importance of diffusion in the adsorption process of some alcohols and acids in dilute aqueous solutions

Abstract With the use of accurately obtained values of static and dynamic surface tensions, the procedure of Ward and Tordai has been followed to investigate the nature of the adsorption mechanism. It was found that with the dilute aqueous solutions of mono-alcohols and mono-acids studied, adsorption at the air-solution interface occurred in each instance at a rate governed by a diffusion process. Some results obtained by other workers are also shown to be consistent with a diffusion mechanism. For the dicarboxylic acid studied (azelaic acid) it is necessary to postulate an activation energy barrier for the latter part of the aging process.

Surface tension of regular solutions

The assumption of a unimolecular layer as the surface phase separating a strictly regular solution from its vapour phase, is in contradiction with the Gibbs adsorption formula. When, however, one takes into account the possible presence of two unimolecular layers inside the surface phase, it is shown that the composition of the layer on the side of the solution differs but little from the composition of the solution itself, a circumstance which justifies the unimolecular layer model as a first approximation. The surface tension is not appreciably altered by this treatment, but the relative adsorption is modified significantly. The formulae thus obtained are no longer in contradiction with the Gibbs formula.

II. Measurement of dynamic surface tensions of aqueous solutions by the falling meniscus method

Abstract The falling meniscus method (based on Rayleighs classical capillary rise equation) is described for the determination of dynamic surface tensions. The work of several previous authors is critically reviewed. The influence of evaporation of solute, the extension of surface area, and the pollution of the surface being studied by contact with an older surface, are discussed, and an apparatus has been designed to eliminate errors caused by these effects. Dynamic surface tensions are reported for aqueous solutions of n-decyl alcohol and capric acid, within the surface age range 1 sec.-1 min.

Correcting surface tension data obtained by the oscillating jet method

Abstract In the first waves of an oscillating jet the velocity of the surface is less than that of the center. Application of Bohrs formula to these first waves gives values of the surface tension which are too high. Hansen and collaborators have proposed an empirical method of correction permitting calculation of the correct surface tension even in this part of the jet. This method, valid for pure liquids, is in the case of solutions subject to errors concerning the true surface age, due to the strong extension in area of each element of surface in the first waves. The authors tested the method used by Hommelen which consists in selecting capillaries which reduce the number of waves to which Bohrs formula is not applicable.

Abbreviated report of the ‘nomenclature and electrochemical definitions’ committee of C.I.T.C.E. and of the ‘symbols and electrochemical terminology’ sub-committee of I.U.P.A.C.

Abstract This is an abbreviated version of the report already published in this Journal (2 (1961) 265-290 and 6 (1963) 173) and was prepared by G. Millazo and P. van Rysselberghe. The translation into English was prepared by R. parasons and is presented here in order that a wider group of electro chemists and electro-analytical chemists may become aware of the direction in which Nomenclature discussions are taking. Comments direct to C.I.T.C.E. (Professor Pierre van Rysselberghe. Department of Chemistry, Stanford University, Stanford, California, U.S.A.) or (if in publishable form), to this Journal, will be welcome.