PHENOMENOLOGICAL INTERPRETATION OF IMPURITY REDISTRIBUTION EFFECTS ONTHE FREEZING CURVE OF OXYGEN

Double freezing curves of oxygen have been obtained in a cooling proce ss with a rate of less than 40 mK/min. The plateaus of these double fr eezing curves show differences in temperature and width. The cause of the observed double freezing curve is presumably redistribution of imp urities into relatively pure and impure regions by transportation duri ng the slow cooling process. This separation is observed in the meltin g curve of oxygen using both continuous and pulse heating methods. We note the importance of impurity redistribution on the accuracy of the temperature measurement and the realization of the triple point of oxy gen.