Viscosities at 25°C have been measured at different molar concentrations for fourteen binary liquid systems representing different types and degrees of interaction between unlike components. Excess viscosities tend to become less negative and then increasingly positive as the strength of the interaction between unlike molecules increases and the excess viscosity is approximately proportional to the strength of the interaction. Some expressions describing viscosities of binary liquid mixtures in terms of those of the components and a parameter attributed to interaction between them are examined. The parameter din the expression In 77 = XI In 71fx2 In 7 2 f x m d appsars to be a useful measure of the strength of the interaction.

Ultrasonic velocities and densities at 25°C have been determined at different molar concentrations for fourteen binary liquid systems representing different types and degrees of interaction between the components. Adiabatic compressibilities are calculated. Excess adiabatic compressibilities tend to become less positive and then increasingly negative as the strength of the interaction between the unlike molecules increases. Excess adiabatic compressibility is approximately proportional to the strength of the interaction. Excess volumes show a similar variation. The variations of excess adiabatic compressibility with composition are generally similar to those shown by other excess properties of binary liquid mixtures.

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Viscosities of dilute solutions of six fractions of polymethyl methacrylate in the molecular weight range of 48,000–400,000 have been obtained with benzene, toluene, chloroform, tetrachloroethane, and n‐amyl methyl ketone as solvents at different temperatures in the range 25–60°C. There is evidence for association of polymer in amyl methyl ketone, and degradation in tetrachloroethane is possible at higher temperatures. Variations of [η] and of k′ with solvent agree generally with those observed by other workers. Where comparison is possible, values of K and a in the expression [η] = KMa are also in general agreement with other values. Values of K′ in the Flory equation [η] = K′M1/2/α3 may possibly vary with solvent, and it is suggested that in cases where solvation of polymer occurs, the chains may be prevented from adopting the unperturbed configuration adopted in less polar solvents. [η] increases with increase of temperature in all cases but that of tetrachloroethane, but there appears to be a maximum value near 53°C. with both benzene and amyl methyl ketone. The variation of the exponent a with temperature is similar to that of [η]. In the cases of benzene and chloroform, the temperature coefficient of [η] seems to be primarily due to changes in the value of the swelling factor α, but in other cases changes in the value of (r̄02/M) are important, r̄02 being the mean square unperturbed end‐to‐end distance of the polymer chains.