Theoretical and experimental analysis of the diaphragm diffusion method for study of the state of trace elements in aqueous
solutions is presented. It is shown that the method has substantial advantages over other diffusion methods and over conventional
use of dialysis, particularly when nucleopore or other membranes with small internal surface area are employed. These advantages
include rather short experimental time, not exceeding tens of minutes, lower adsorption losses and lower shift of equilibria
among various forms of the trace element studied. A new method for the continuous measurement of and for the evaluation of
diffusion is suggested, which enables calculation of the abundance of colloidal forms of the element. Verification of the
method is carried out for a particular case using trace radiocerium.
Theoretical and experimental analysis of the open-ended capillary diffusion method for study of the state of trace elements
in aqueous solutions is presented. It is shown by theoretical considerations that the use of the discontinuous capillary method
of diffusion and the evaluation of single measurements using the classical Anderson-Saddington equation yields incorrect diffusion
coefficients if two or more forms of the trace element with significantly different diffusion characteristics are simultaneously
present in the solution. A new method for the evaluation of diffusion is suggested, which enables calculation of the abundance
of two different forms of a trace element. The method employs a continuous measurement of diffusion combined with computer
analysis of the data obtained. Verification of the method is carried out for a particular case using trace radiocerium. The
effect of adsorption on the diffusion measurement and interpretation is discussed.
The method of constant velocity supply of the radioactive labelled component into the system was used to study the kinetics
of the isotope exchange Tl(I)-hydroxyquinolate-Tl(III)-hydroxyquinolate in chloroform. The second order exchange reaction
with a halftime less than 1 min was determined in the range of concentrations 0.2–2·10−3 M of both components.
This paper presents the method of double labelling in the study of the kinetics of homogeneous isotope exchange reactions.
This method was tested by the determination of the Sn(II)−Sn(IV) exchange rate in hydrochloric acid medium. The system was
labelled by the tracer119mSn [initially in the Sn(IV) state]; when the isotope equilibrium was established, Sn(IV) was again labelled by tracer113Sn. The separation of Sn(II) and Sn(IV) in the given time of exchange was performed by the extraction of Sn(IV)-hydroxyquinolate
into chloroform. The specific activities of the separated components were determined from the ratio of113Sn and119mSn activities. The exchange rate was calculated from the time dependence of specific activities. The advantage and possibilities
of the method of double labelling in the study of isotope exchange are discussed.
Authors:J. Sedláček, A. Gosman, P. Podhájecký, and J. Tarasová
This paper is concerned with the study of isotope exchange reaction between Sn(II) and Sn(IV) in hydrochloric acid solutions.
The kinetics of the exchange reaction of tin in these solutions were studied by extraction of Sn(IV)-hydroxyquinolate into
chloroform.113Sn tracer, initially in the Sn(IV) state, was used. The rate of exchange reaction was determined at 22°C in a wide range of
hydrochloric acid concentrations (2.8–12M). The dependence of the exchange rate on the concentration of chloride and hydrogen
ions in these solutions (ionic strength: I∼8 and I∼12) are given. The activation energy dependence on chloride ion concentration
at I∼12 was determined. The possible mechanism of the exchange reaction between tin(II) and tin(IV) is discussed on the basis
of these data.