THERMAL CONDUCTIVITIES of most pure organic liquids vary with temperature in the manner shown in Figure 1, where the abscissa indicates the fractional distance of the saturated liquid from melting point to critical point. On the scale the normal boiling point is usually around e = %. During the past 40 years the number of measurements of liquid conductivities has greatly increased, but all except a few fall in the region below the boiling point, where the variation with temperature is practically linear. The part of Figure 1 above e = % is based on data for eleven liquids obtained by five observers (1-3, 16, 23). Conductivity in the absence of measured values can a t present be calculated by one or another of varyingly successful methods (11, 20) as long as one does not go beyond the linear region (0 less than approximately 0.7). Because of the scarcity of data on any liquid properties a t higher temperatures, none of the methods of prediction has been tested properly for 8 > 0.7. The purpose of the present work was to measure the conductivities of some representative compounds a t these higher temperatures, to establish more firmly the general behavior in this region and to aid in the development of methods of prediction in the absence of direct data. APPARATUSFor the conductivity measurements a steady-state, thinfilm apparatus was used. The conducting liquids were contained in three concentric annular spaces (Figure 2). The cylindrical shape was chosen for convenient control of heat losses as well as adaptability to a high-pressure system. The principle of the thin film to control convection is well known, having been applied by most previous workers, regardless of the shape of the apparatus. Three films in series were used in this work, to increase the magnitude of the basic temperature drop and its accuracy of measurement while meeting Kraussold's criterion for absence of convection.The apparatus was made entirely of stainless steel to km k hc IS OF THE ORDER OF$ km 0 I Figure 1. Typical variation of thermal conductivity of a liquid with temperature QLAm N E WQlWO RESISTME WIRE REFRACTORY TueE THERMOCOUPLE WELL Figure 3. High-temperature experimental arrangement -+