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New vapor pressure measurements have been made using D sub 2 + 0.84% HD and exp 20 Ne. Temperatures were determined using the vapor pressure equations of Grilly and Furukawa and the 4.21 exp 0 K He point to determine a resistance vs. temperature function for the platinum thermometer. This function was compared to the original calibration. Another measurement of D sub 2 + 0.18% HD displays a smaller difference from the D sub 2 + 0.84% HD data than expected from the compilation of Woolley, Scott and Brickwedde. This work is a product of establishing a temperature scale at our laboratory in the region between 12 and 30 exp 0 K to measure vapor pressures of mixtures of ortho and para D sub 2 . We found that it was necessary to know the amount of HD in the samples to 0.01%. It appears that in all previous measurements of the vapor pressure of D sub 2 , even in chemically pure samples, there was an unknown amount of HD. Thus, we have made measurements on a sample of normal D sub 2 + 0.84% HD, to be compared to the D sub 2 measurements of Grilly, and a new measurement of exp 20 Ne. This was done to improve on the thermometry used in the vapor pressure measurements of the neon isotopes.