AbstractsChemistry

When two organic liquids are missed the resulting physical properties of the solution nearly always differ from those calculated on the assumption of an additive relationship. The extent of these deviations varies widely with the nature of the liquids chosen, and where there is a large evolution of heat it is considered that molecular compound formation has occurred. Some binary mixtures of phenols with aromatic bases have been investigated by Bramley (1) and are of this type. Macleod (2) has derived an expression for the viscosity of a binary mixture which has undergone volume change and compound formation. The expression contains the factor Ma/Mc, where Mc is the calculated mean molecular weight of the constituents and Ma is the actual mean molecular weight after mixing. By using Bramley’s density and viscosity results Macleod has evaluated Ma/Mc for the binary system aniline – o-chlorophenol. Bramley has determined the freezing-poing curve for this system, showing the existence of an equimolecular compound, and so Macleod has been able to calculate the number of double molecules required to give the ratio Ma/Mc. He has also calculated the equilibrium constants for a number of temperatures; using the amount of compound formation found from the viscosity formula at the equimolecular percentage and assuming the law of mass action to hold. The object of this work is a determination of the heats of reaction of this mixture at several temperatures, enabling the equilibrium constants to be calculated directly. The comparison of these constants with those obtained by Macleod from viscosity data should afford a check on his equation for the viscosity of binary mixtures. The formula for the calculation of the heat of reaction from the temperature rise necessitated knowledge of the specific heat of the mixture. It was therefore necessary to determine the specific heat curves at definite temperatures. These results, besides being necessary for the heats of reaction, also enables the partial molal heat capacities to be calculated. Further, so investigation of the literature shows that there are at present several different theories as to the nature of the link in this of compound. As the various theories depend partly upon the refractive index, it was decided to measure this property for the mixture. This work, together with refractive index measurements in hydrated mixtures, forms the second part of the thesis.