International Journal of Thermophysics, Vol. 4, No. 4, 1983 Thermal Conductivity of Toluene in the Temperature Range 35-90~ at Pressures up to 600 MPa C. A. Nieto de Castro, 1 S. F. Y. Li, 2 G. C. Maitland, 2 and W. A. Wakeha Received December 14, 1983 New, absolute measurements of the thermal conductivity of liquid toluene are reported. The measurements extend over the temperature range 35-90~ and the pressure range 0.8-600 MPa. A new analytic evaluation of the contribution of radiation in an absorbing emitting fluid to the measurement process is presented. This analysis indicates that the thermal conductivity determined in a transient hot-wire instrument is the radiation-free value. As a consequence it is possible to assert that the overall uncertainty in the experimental data is one of + 0.3%. A comparison of the data with the results of independent measurements by the same technique shows that the various sets of data are consistent within their mutual uncertainty. KEY WORDS: high pressure; thermal conductivity; toluene; radiation contri- bution. 1. INTRODUCTION In a number of earlier publications [1-4] we have reported the results of measurementsof the thermal conductivity of liquids over a moderate temperature range and at pressures up to 600 MPa. The measurements have been carried out by the transient hot-wire technique, which is capable of high precision [1]. However, the accuracy which it has been possible to claim for the final results has been inferior to their precision owing to the contribution of radiative heat transfer in an absorbing fluid to the measure- ment process [5]. The contribution of radiative heat transfer to thermal conductivity measurements on absorbing liquids hasbeen the subject of l Centro de Quimica Estrutural, Complexo I, Instituto Superior Tecnico, Lisbon, Portugal. 2Department of Chemical Engineering and Chemical Technology, Imperial College, London S.W. 7 2BY, England. 311 0195-928X/83/1200-0311503.00/0 01983 Plenum Publishing Corporation