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The thermal decomposition of nitrous oxide (N.O) was studied in a single-pulse shock tube in the temperature range 1300 to 1950 OK at a total concentration of 2 x 10-5 molcsjcc, The Arrhenius rate constant for the react ion N .O + M~N. + 0 + M is given by k , = 10 13 . t exp (-44,tOO/RT) cc/mole sec. The ratio of the rate constants for the two competing secondary reactions, N.O + 0~N. + O. and N.O + 0~NO + NO, was also determined and was found to be ka/k. = 0.50. The overall rate of N,O decomposition is also discussed and the results of previous invest igators are compared to the find ings reported here.

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Heat transfer through gases contained between vertical concentric cylinders was investigated when the radius of the inner cylinder is small compared to the radius of the outer cylinder. Experiments were performed in a modified hot wire type thermal conductivity cell in which end effects could be evaluated in addition to the overall heat transfer between the cylinders. Measurements were made with argon, hetium and neon in the pressure range 0.1-620 mmHg, for the temperature differences between the cylinders of 10, 50 and 100 degC, and for the length to the outer diameter ratios between 3.3 and 6.7. The results show that below certain Rayleigh numbers and length to diameter ratios heat is transferred from the hot to cold boundary by conduction only. End effects contribute only in the corner regions. The distance to which these end effects penetrate was determined experimentally, and compared to analytical results obtained from a simple heat balance in the corner region. Relationships, based on the experimental data, were also obtained for the average heat transfer both in the corner regions and over the entire length of the cylinders. It is shown that these results may be used to estimate the error introduced in thermal conductivity and thermal accommodation coefficient measurements by neglecting end effects. NO~NCLATURE radius of inner cylinder [cm] ; radius of outer cylinder [cm] ; specific heat [W/g degC] ; diameter of outer cylinder [cm] ; gravitational acceleration [cm/s21 ; heat-transfer coefficient [W/cm degC] ; distance between potential leads [cm] ; thermal conductivity [W/cm degC/cm] ; heat flow per unit length [W/cm] ; heat flow [W] ; radial coordinate [cm] ; actual length of cylinders [cm] ; temperature ["Cl ;