Estimation of diffusion coefficients by a capillary method in the presence of oppositely directed convection of the melt

1987 ◽  
Vol 37 (8) ◽  
pp. 924-932
Author(s):  
P. Kubíček ◽  
B. Wozniaková
Keyword(s):  
Diffusion Coefficients ◽  
Capillary Method

The precision measurement of single ion diffusion coefficients

1958 ◽  
Vol 11 (1) ◽  
pp. 1
Author(s):  
R Mills ◽  
EW Godbole
Keyword(s):  
Precision Measurement ◽  
Diffusion Coefficients ◽  
Electrolyte Solutions ◽  
Radioactive Material ◽  
Ion Diffusion ◽  
Capillary Method ◽  
Dilute Electrolyte Solutions

The precision measurement of single ion diffusion coefficients in dilute electrolyte solutions would be of considerable value. A method is described which is capable of giving the required precision. It involves a modification of the open-ended capillary method by enclosure of the capillary of diffusing radioactive material in a scintillator so that its contents can be continually monitored during the course of diffusion.

Self-diffusion in molten sodium chloride: a test of the applicability of the Nernst—Einstein equation

1957 ◽  
Vol 241 (1227) ◽  
pp. 554-567 ◽  
Keyword(s):  
Sodium Chloride ◽  
Einstein Equation ◽  
Diffusion Coefficients ◽  
Liquid Sodium ◽  
Einstein Relation ◽  
Transport Numbers ◽  
Self Diffusion ◽  
Capillary Method ◽  
Molten Sodium ◽  
The Individual

Self-diffusion coefficients of sodium and chlorine in molten sodium chloride have been determined by the capillary method with the aid of 22 Na and 36 Cl radio-tracers. The results can be represented by the expressions D Na = 8x 10 -4 exp (-4000/RT) and D Cl = 33 x 10 -4 exp (-8500/.RT). These values, when inserted in the Nernst-Einstein equation (A = (F 2 /RT) (D+ D-)), lead to a value of the equivalent conductance, A, which is about 40 % greater than that observed experimentally. The evidence that the diffusion coefficients of Na + and Cl - are similar in magnitude and that the activation energies are much smaller than the heat of vaporization of liquid sodium chloride, support the conclusions, derived from other evidence, that the free volume in the molten salt consists largely of holes, analogous to vacant lattice sites. On the basis of this model, the discrepancy in the Nernst-Einstein relation can readily be interpreted in terms of two diffusion mechanisms, one being normal vacancy diffusion of single ions, and the other a process in which no net charge is displaced in a unit step. It is suggested that the latter is the Seitz-Dienes mechanism of consecutive jumps of cation and anion in coupled vacancies. The interpretation mentioned enables the individual mobilities of Na + and Cl - ions to be determined, and hence their transport numbers can be calculated (t Na += 0.71, t Cl - = 0.29 at 935° C). The individual diffusion coefficients of the ions and of the coupled vacancies are in reasonable agreement with the Stokes-Einstein equation.

scholarly journals Study of the diffusion of metals and metals-EDTA complexes in water by capillary method

2021 ◽  
Vol 290 ◽  
pp. 01004
Author(s):  
Zilong Geng ◽  
Hui Chen ◽  
Chenyu Yang ◽  
Qiang Shen ◽  
Tao Wu
Keyword(s):  
Metal Ions ◽  
Diffusion Coefficients ◽  
Safety Assessment ◽  
Ionic Radius ◽  
Molecular Size ◽  
Einstein Relation ◽  
Water Molecules ◽  
Capillary Method ◽  
Hydrated Ions ◽  
Edta Complexes

EDTA can complex with radionuclides (RNs) to form negatively charged complexes, making it difficult for clay minerals to retard the diffusion of RNs waste. The diffusion coefficient of RNs in water (Dw) is an important parameter for the safety assessment of the repository. In this study, the effectsof EDTA on the diffusion of metal ions (Cu2+, Sm3+, Nd3+, Lu3+ and Zn2+) were investigated by a capillary method. The experimental results showed that [Cu-EDTA]2-, [Sm-EDTA]-and [La-EDTA]-have higher Dw thanthe Mn+. Whereas, [Nd-EDTA]-and [Zn-EDTA]2- have lower Dw than Nd3+ and Zn2+ cations. The Dw is consistent with the literatures, indicating the validity of the capillary method to determine the diffusion coefficients. According to Stokes-Einstein relation, the ionic radius and ionic potential of the ion are in disproportional to the Dw value. Cu-, Sm-and La-EDTA complexes have smaller molecular size than the uncomplexed metal ions, indicating that the Mn+ ions might be associated with many water molecules to form hydrated ions with larger ionic radius. Whereas the [Nd-EDTA]-and [Zn-EDTA]2- have larger molecular size than Nd3+ and Zn2+ cations.

Self-Diffusion Coefficients in Molten AgNO3-NaNO3 and AgNO3-KNO3 Mixtures

1973 ◽  
Vol 28 (1) ◽  
pp. 51-57 ◽  
Author(s):  
Stefania Zuca ◽  
Mariela Constantinescu
Keyword(s):  
Temperature Dependence ◽  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
The Self ◽  
Linear Variation ◽  
Self Diffusion ◽  
Capillary Method ◽  
Ionic Size

The self-diffusion coefficients of the constituent cations in the systems (Ag-Na)NO3 and (Ag-K)NO3 have been investigated by the "diffusion-into-the capillary" method at three concentrations (xAgNO3 = 0.25; 0.50; 0.75) and at temperatures ranging from 250 to 400°. A temperature dependence given by the Arrhenius equation and an almost linear variation with composition were observed. The correlation existing between the ionic size of diffusing cations and the diffusion coefficients in these melts is discussed.

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