Determination Of Transport Numbers Research Articles

Bestimmung von ionenbeweglichkeiten in nichtwässrigen elektrolytlösungen—I: Die messung der überführungszahl der na-ionenkomponente in wasserfreiem methanol nach dem radio-isotopenverfahren mit hilfe des γ-strahlers 24Na

The use of radioisotopes for the determination of transport numbers by the moving boundary method has been shown to be applicable in non-aqueous media. The transport number of the sodium ion in 0.01 M sodium chloride in dry methanol was determined using γ-emitter 24Na, and the results are in good agreement with those obtained by other means. The accuracy of the technique and its advantages over optical methods are discussed.

Electrical transport phenomena in a cation-exchange membrane: I. The determination of transport numbers and the ratios of tracer fluxes

The transport numbers of the mobile ions have been determined in a phenol-sulfonic cation-exchange membrane under conditions of constant chemical composition. Measurements have been made at 25°C and at a number of external concentrations in the range 0.01–1.00 equiv/l with the membrane in the Na +, Cs +, and Sr 2+ states. In all cases the external solutions were bromides. Measurements were also made over the whole composition range at 0.02 and 0.10 equiv/l in the Na + + Cs + and Na + + Sr 2+ mixed cation states. Constant composition was maintained by using radiotracers to follow the fluxes in a multicompartment cell. Results are reliable to ± 1%. The co-ion transport number was relatively much larger when the resin contained bivalent rather than univalent counterions because the mobility of the counterions was lower and the concentration of the co-ions higher. In the mixed counterion states the transport number of the thermodynamically preferred counterions was especially low when they were present in small amount. This would lower the efficiency of an electrodialytic counterion separation process. Experiments on the mixtures of uni- and bivalent counterions at low total concentration were seriously affected by polarization at the membrane/solution boundaries. This effect would further restrict an ion separation process. the mechanism of this polarization is discussed. The measurements have also provided data on the ratios of the tracer fluxes with and against the electric current. A nonequilibrium thermodynamic treatment of this flux ratio is given. It is shown to be related to the transport numbers and tracer diffusion coefficients in a simple way. This relation was tested by making use of the tracer diffusion coefficients determined previously. In general the agreement with theory was satisfactory. Failures were due to polarization, which has a greater effect on the tracer flux ratio than on the transport number, i.e., the tracer flux difference.

The chronopotentiometric determination of transport numbers

The expression for the transport number of an ionic species has been derived from the chronopotentiometric transition time at a spherical micro-electrode in the absence of supporting electrolyte. The transport number is related to the transition time and to the diffusion coefficient of the salt, or alternatively, it is expressed in terms of the transition time and the equivalent conductivity of the salt at infinite dilution. These expressions have been examined in relation to two types of system (i) dilute aqueous solutions of thallous chloride and (ii) anhydrous solutions of thallous perchlorate in N,N-dimethylformamide. In both cases, the experimental results conform to the proposed relationships and in each, transport numbers have been evaluated in good agreement with those obtained independently. The results confirm that “single-salt chronopotentiometry” is a rapid, satisfactory, albeit approximate, method of determination of transport numbers.

A Moving Boundary Method for the Determination of Transport Numbers in Pure Fused Salts

A method is described for determining the transport numbers in fused salts by visual observation of the boundary between the salt under investigation and a following indicator salt. (W.L.H.)

An investigation of the analytical boundary method for the determination of transport numbers

An investigation of the analytical boundary method for the determination of transport numbers

141. Automatic adjustment of solute concentration in the “moving-boundary” method for the determination of transport numbers

The first page of this article is displayed as the abstract.

A new method for the determination of transport numbers. Part III.—The balanced boundary apparatus

A new method for the determination of transport numbers. Part III.—The balanced boundary apparatus

A new method for the determination of transport numbers. Part II.—Exploratory

A new method for the determination of transport numbers. Part II.—Exploratory

A new method for the determination of transport numbers. Part I.—Theory of the method

A new method for the determination of transport numbers. Part I.—Theory of the method

The moving boundary method for the determination of transport numbers

The lack of a simple and fairly complete theoretical treatment of the moving boundary method has been felt in this laboratory in the course of transport number measurements in dye solutions. The results of these measurements are shortly to be published by Dr. C. Robinson and one of us (J. L. M.). In the present paper we shall attempt to develop a theory of the method, of necessity including some previous work, and to explain experimental results in the literature and the aforementioned work on dye solutions. Doubts have been expressed as to the validity of the method, in spite of the convincing experimental work of MacInnes, Smith, Longsworth, and co-workers, to whom we shall frequently have occasion to refer. These attacks on the method, we believe, have arisen from a misunderstanding of the fundamental principles involved, and we shall endeavour to answer them in this paper. In order to avoid confusion, we shall first explain the terminology to be used, which we hope will be adhered to in future communications from ourselves and coworkers. In this paper we confine ourselves to electrolytes (including colloidal electrolytes). The application of the method to colloids will be the subject of a future communication from this laboratory.

The Use of Micro-Coulometers in the Determination of Transport Numbers by the Moving Boundary Method

The Use of Micro-Coulometers in the Determination of Transport Numbers by the Moving Boundary Method

III. The measurement of Ionic velocities in aqueous solution, and the existence of complex ions

As early as 1853 Hittorf (‘Pogg. Ann.,' vol. 89, 181, 1853), discussing the results of his experiments, emphasised the fact, that a more detailed study of the movements of the ions during electrolysis would result in an increased knowledge of the constitution of salts in solution. He himself, in a research extending over a number of years, ( ibid ., 89, 177, 1853; 98, 1, 1856; 106, 337 and 513, 1859,) determined the ratio of the velocities of the two ions for a large number of salts, and the series of measurements has been further extended by later investigators. (For the original literature on transport number determination, see Bein, 'Zeitschrift fur Phys. Chemie,' vol. 27, 1 (1898)).