The thermal conductivity of nitrogen is determined in a conductivity column instrument in the temperature range of 338 to 2518 K with an estimated uncertainty of about _+1"5 per cent. The experimental data points are correlated by a cubic polynomial in temperature, viz. k(T)/(mW m -1 K -1) = 12.18 + 0"05224(T/K) -0"6482 x 10-6(T/K) 2 -0"2765 x 10-9(T/K) z. These conductivity values determined from heat transfer data taken in the continuum regime are found to be in fair agreement with the values obtained from similar data referring to low pressure range.The present results are compared with the conductivity determinations of other workers and with the predictions of various theories developed for polyatomic gases. It is pointed out that a reliable calculation of thermal conductivity over an extended temperature range is impossible at the present time due to the absence of a large variety of experimental molecular data needed for such an effort. Average values of the vibrational energy diffusion coefficient, Dvib, are computed from the present k(T) data.

The thermal conductivity of argon is determined in the temperature range 350-2500 K in a carefully designed conductivity column and is given by k(T)/(mW m -x K -x) = 5"465 + 0"04729(T/K) -0"1111 x IO-~(T/K) ~ + 0"1599x 10-S(T/K) a within an estimated uncertainty of about + 1"5 per cent. These values, which are derived from heat transfer measurements in the continuum range, are compared with conductivity values obtained from similar data taken in the temperature-jump regime. The k values are also compared with other available conductivity and viscosity data, and with the predictions based on kinetic theory in conjunction with intermolecular potentials, and the principle of corresponding states. These comparisons have led to many interesting conclusions concerning the quality of other experimental data and the appropriateness of different intermolecular potentials. The predictions based on corresponding states appear most reliable.