Abstract
Abstract Aqueous solutions of HCl, inorganic salts, and neutral and ionic organic compounds were frozen, and the solute distribution in the frozen systems was assessed in terms of its dependence on composition and initial solute concentration. The distribution may be uniform or uneven, depending on compositional aspects of the solutions. The degree of non-uniformity of the distribution of a given solute is a function not only of its own initial concentration but also of the concentration of any additional solute. With a variety of two-component solutions, maximally uneven solute distribution was found to be associated with approximately the same initial concentration (about 10-4 m, under the conditions of these experiments). As the concentration was raised above this level, the distribution of solute became increasingly more uniform; this was similar for all solutes. Upon lowering the concentration below this level, the tendency toward uniformity of distribution varied with the solute. With multicomponent systems, reciprocal effects of the concentration of one solute on the distribution of another were noted. In producing these effects, the absence or presence and sign of electric charge borne by the solutes seems to play no major role at concentrations higher than the optimal concentration for maximal nonuniformity of distribution. Electric charge and the specific nature of the solute may be important determinants of solute redistribution at very low concentrations.
Highlights
Aqueous solutions of HCl, inorganic salts, and neutral and ionic organic compounds were frozen, and the solute distribution in the frozen systems was assessed in terms of its dependence on composition and initial solute concentration
Freezing of a solution leads to a redistribution of solute because it is rejected by the crystallizing solvent [1]. This phenomenon underlies a number of techniques for purifying ice [2], or concentrating solute [3,4,5], from aqueous solutions
Since halide salts are well capable of generating a freezing potential, it seemed of interest to establish whether any correlation existed between values of K’ of KC1 and of an additional solute, and the freezing potential
Summary
Aqueous solutions of HCl, inorganic salts, and neutral and ionic organic compounds were frozen, and the solute distribution in the frozen systems was assessed in terms of its dependence on composition and initial solute concentration. Freezing of a solution leads to a redistribution of solute because it is rejected by the crystallizing solvent [1] This phenomenon underlies a number of techniques for purifying ice [2], or concentrating solute [3,4,5], from aqueous solutions. The principal objective of the experiments was to identify the general nature of some of the patterns of solute distribution, produced by freezing of aqueous solutions the composition and concentration of which were varied. 1. Redistribution of protons upon freezing of aqueous lo+ N HCI containing varying concentrations of KCl. The immersion technique of freezing was used and fractions were collected during melting. The experimental points represent the averages of duplicate experiments; the mean deviation of individual data from their respective averages was 7% of the indicated acid concentration
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