When studying the interaction between solution components, it becomes necessary to compare exper imental composition-property curves with the corre sponding curves calculated assuming that there is no interaction between the components, but with allow ance for the changes experienced by each component in the selected solvent [1,2]. Constructing composi tion-property curves under assumption that there is no inter component interactions requires one to know equations for the dependencies of the corresponding properties of the solutions of individual components in a given solvent on their concentration in the solution. The equations for the polarization plane rotation in aqueous solutions of D (+) tartaric acid ( ) as a function of its concentration and for the depression in freezing point (ΔT fr and pH of aqueous solutions as a function of concentrations of both D (+) tartaric acid and sodium tungstate were ascertained previously [3]. This work is devoted to studying the rotation value ( ), the decrease in freezing point (ΔT fr ), and pH values of aqueous solutions as dependent on the con centrations of sodium tungstate and D (+) tartaric acid in the presence of HCl and NaOH. The results of these studies are extremely important for investigating the effects of the medium on the product of interac tion between sodium tungstate and D (+) tartaric acid due to the fact that the composition of the result ing anionic complex in this system has not been unam biguously elucidated [3][4][5][6][7]. EXPERIMENTAL Bidistilled water, D (+) tartaric acid, and sodium tungstate (analytical purity grade), which had been additionally purified by recrystallization from aqueous solutions, were used to prepare the solutions under investigation. The solutions for polarimetric measure ments performed on an SM 2 polarimeter (±0.02°a ccuracy) and for pH measurements were prepared in 20 D ∝ 20 D ∝ 25 mL volumetric flasks; flask volumes had been pre liminarily determined at 293.15 ± 0.02 K with accu racy of ±0.01 mL. pH values were measured on a pH 673M high resistance potentiometer with accuracy of ±0.02 pH units. Hydrochloric acid solutions were pre pared from a standard solution; the concentration of carbonate free sodium hydroxide was determined by titration. Cryoscopic measurements were carried out on a Beckman cryoscopic apparatus; the accuracy of temperature measurements was ±0.002 K.RESULTS AND DISCUSSION Plots of the polarization plane rotation angle of solutions of D (+) tartaric acid ( ) as a function of its concentration in the corresponding solutions are shown in Fig. 1. Curve 1 demonstrates the polariza tion plane rotation angle of aqueous solutions of D (+) tartaric acid as a function of its concentration, which can be well described by the following relation ship [8]:(1)where C M is the molarity of an aqueous solution of D (+) tartaric acid, orwhere C is the number of grams of optically active tar taric acid in 100 mL of the solution.Curves 2 and 3 characterize the polarization plane rotation angles of the solutions as a funct...
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