Precise cryoscopic determination of osmotic coefficients for solutions of some alkali metal salts in dimethyl sulphoxide and in sulpholane

Abstract

An apparatus is described for the precise measurement of freezing-point depressions for nonaqueous solutions by a heating curve method. The apparatus has been used for measurements on solutions in dimethyl sulphoxide and in sulpholane (tetrahydrothiophene-1 ,l-dioxide), the relevant physical properties of which are critically discussed. Osmotic coefficients have been determined with an accuracy of 0.2-1 % for solutions of some alkali metal perchlorates and of lithium chloride. The salts studied behave differently in the two solvents. The ionic solvating power of dimethyl sulphoxide is much greater than that of sulpholane, which results in opposite sequences of osmotic coefficients for the alkali metal perchlorates, and striking differences in degrees of ion association in the two solvents, particularly for lithium chloride. The interpretation of these observations is discussed, together with the behaviour of lithium halides in a range of solvents.

The Activity Coefficient of Lithium Chloride in Anhydrous Dimethyl Sulfoxide Solutions

“…[2] is replaced by a factor of 4, and when combined with Eq. [1] this yields Oobs 8eorr = -- [5] 1 --4Q with the same value of Q as derived above.…”

“…A more direct comparison can be made in terms of the function (8) Fig. 3 our results are compared with those of Dunnett and Gasser (3) and Garnsey and Prue (5). By numerical integration we also obtained j as a function of m, corresponding to the best fit to the emf data ( Fig.…”

“…Osmotic coefficients were calculated from the values of 0corr using the equation (5,8) Too 2~m (To --o) with To = 18.55~ and with a cryoscopic constant (5) = 4.07~ These osmotic coefficients are also listed in Table II. Activity coefficients were not calculated from these cryoscopic measurements because of the large errors inherent in the smoothing and integration required. Instead the cryoscopic and electrochemical measurements were compared in terms of the integration function j, as described in the next section.…”

Hydration of Some Acids in Sulfolane

“…Precise and extensive cryoscopic determinations of molal freezing point depressions of organic solutes in Sulfolane by Della Monica et al (14) revealed that the constants for benzoic acid from 0.1 to 1 M are identical to those of diphenylmethane, naphthalene, and benzene which are not expected to dimerize. We also found that the molal freezing point depression constant for 0.01 M acetic acid in Sulfolane as determined by using the LKB calorimeter was 64 + 2" compared to normal values of 65" (14) and 64" (15) for nonassociating substances. Furthermore, the heats of mixing with Sulfolane given in Table 1 for acetic acid and the substituted acetic acids, in the range 0.02 to 0.4 M acid, are' constant within 50.02 kcal per mol acid.…”

Solubilities of the silver halides in propylene carbonate mixtures with bis(trifluoroethyl)sulfite

“…The cell capacitance was measured by a substitution method using a General Radio 1606-B bridge and Type 722-D and 1422-ME precision variable capacitors. The cell constants were determined from measurements made with air (7), benzene (8), PC (6), and dimethylsulfoxide (9). A leastsquares fit gave where C is the measured capacity and E is the static dielectric constant.…”