EFFECT OF TEMPERATURE ON THE ELECTRICAL CONDUCTANCE OF HYDROGEN CHLORIDE IN DIMETHYLSULPHOXIDE*

-The electrical conductance of solutions of hydrogen chloride in dimethylsulphoxide at temperatures from 25 to 45°C has been studied. for associated l-l type electrolytes. Results have been interpreted with the Fuoss theory Values of the association constant K, and the J parameter have been computed at each temperature. The temperature dependence of the molar conductance is inferred from the theoretical equation and related to the temperature dependence of viscosity. R&s-&La conductance Clectrique des solutions de chlorure d’hydrog&ne dans le dimtthylsulfoxyde ;1 des tempdratures de 25 a 45°C a 6t6 &udi&e. pour des electrolytes associkes du type l-l. Les rbultats ont &C inteprttts par la th6orie de Fuoss Les valeurs de la constante d’association K, et du para-m&re J ont Bt6 calcul6es g chaque temp&ature. La dtpendance de la conductivit6 molare avec la

The   'have practically the same absolute value, the Walden product &qO, where A,, is the limiting molar conductance and r], the solvent viscosity, should be temperatureindependent as observed in Table 6.On the contrary, from TabIe 1 it is seen that the product A?, at constant temperature, depends on concentration.
This shows that the mechanisms of the above processes are differently affected by ionic interactions, which must play an increasing role at higher concentrations, particularly in the mechanism of electrical conduction.The meaning of each term is given in Fuoss' original paper.6From (l), the equilibrium constant of the ionic association process, K b, and the J parameter, are determined.J is directly related to a, the mean distance of nearest approach of the pairs of ions.

DISCUSSION
As already indicated, the evaluation is made by successive approximations.An initial value of A, calculated by Shedlovsky's equation is chosen.6The procedure indicated by Fuoss is then followed until a set of X, y values representing a straight line is found.If the plot bends downward, a new lower value is chosen, and the procedure repeated until necessary.If the plot bends upward, a higher value of A, is selected.The constants for using (1) at different temperatures are assembled in Tables 6 and 7. Table 7 also includes values of the dielectric constant of the solvent, D, the limiting molar conductance calculated with Shedlovsky's equation, and parameters obtained with (I).From decreases other l-l Table 7 two imp&ant facts are deduced.First, the dissociation constant slightly with the temperature.This effect is similar to that observed for type electrolytes, such as acetic acid in water.sBy applying the Kirchhoff (2) the expressions or and a2 are given in the literaturees Table 7 shows that J varies inversely with D at constant temperature.
From J, the mean ionic radius calculated

IN
E&LIW papers the electrical conductance of solutions of hydrogen chloride in DMSO has been studied at ~?J"C.~*~It has been observed that HCl behaves in this solvent as a markedly associated l-l type electrolyte, its association constant K* being 1157 l/mole.This behaviour is dissimilar with that of other electrolytes of the same type in DMSO,S which are completely dissociated strong electrolytes over a rather large range of concentration.It is then of interest to extend previous work on this matter to other temperature and viscosity ranges, to discover the energetic peculiarities of the mechanism of electrical conduction. of the electrical conductance are assembled in Tables l-5.K is the specific conductance and C the molar concentration.At each temperature, concentrations were corrected for density changes and the molar conductances A were calculated accordingly.The dependence of the molar conductance with concentration is shown in Fig. 1, where it is pIotted vs C112 at different temperatures.Figure 2 shows results of viscosity measurements, in a plot of the viscosity coefficient 7 w Pa, for each temperature.
molar conductance increases monotonously with decreasing concentration at all temperatures, as already reported for 25OC,* while at constant concentration it increases with the temperature, following as a first approximation an Arrhenius equation.On this basis average values of the experimental activation energy for conductances , AHA*, are calculated.These values lie between 3-2 & 063 and 2-4 f O-3 Kcal/mole.AH, * tends to decrease with increasing concentration, as shown in Fig. 3, Viscosity also decreases with concentration and temperature.Figure 4 shows these results.In a plot of log q US l/Tslightly bent curves are obtained for all concentrations, but the average experimental activation energy for viscosity, AHq*, is 3-O & O-1 kcal/mole, for the pure solvent and for all the range of concentrations studied, can be calculated.These results indicate that at least at infinite dilution, where AH,* and AH,* On the basis of the interpretation advanced in a previous paper," the results are now discussed with the Fuoss theory for associated l-l type electrolytes.5The following general equation applies in the range from 25 to 45"C, A, = A, -S(C#/2 + ECy log (Cy) + JCy - FIG. 1. Plot of the molar conductance A us 2/C at different temperatures.0,25"C; A, 30°C; .,35"C;(),4O"C;q ,45"C.

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for the range of temperature and concentration of the present work results, a = t(2.3f 0.3) x lo-* cm, this figure being practically temperature-independent.The ,degree of dissociation, y, shownin the TabIes was also calculated with Fuoss'procedure.