| Summary: | The liquid state is discussed with reference to its importance in determining the transport properties. Existing quasi gaseous and,quasi crystalline theories of energy transport in liquids are outlined and their predictions for simple molecular systems discussed. The methods available for measuring thermal conductivity have been critically surveyed and the advantages of the selected transient conduction method are presented and analysed in detail. In addition to measurements upon the well studied compounds toluene and water the group of compounds benzene, diphenyl, ortho-, meta- and para-terphenyl and triphenylene have been studied over a range of temperature including the supercooled state. The thermal conductivities and viscosities of the isotopically substituted pairs benzene and perdeuterobenzene, cyclohexane and perdeuterocyclohexane have been measured. Existing diffusion data on ethyl iodide n-butyl iodide mixtures have been supplemented by viscosity and thermal conductivity measurements. In Part 3 existing theories of liquid thermal conduction are extended for liquids containing simple molecules. An expression is derived in terms of a mean molecular vibration frequency calculated from known pair forces assuming a quasi crystalline liquid structure,. A close relationship between the temperature coefficient of thermal conductivity and the thermal expansion coefficient is indicated. The contrasting behaviour of energy and momentum transport in molten polyphenyls is discussed and the thermal conductivities compared with the existing theories. The ratios of the transport coefficients of energy and momentum in isotopically substituted benzene and cyclohexane are discussed with reference to mechanisms of transport in condensed phases and the experimental results are compared with a specific model due to Valleau. Some relationship between the transport coefficients of mass momentum and energy in binary regular solutions have been extracted from a theory of Bearman and compared with the values obtained experimentally for ethyl iodide, n butyl iodide mixtures,
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