Transformations of Ice II, Ice III, and Ice V at Atmospheric Pressure

The transformations that occur in ices II, III, and V at atmospheric pressure when they are heated from liquid-nitrogen temperature have been examined by simple thermal analysis and by x-ray diffraction. They transform first to cubic ice I (ice Ic). The rate of transformation of ices II and III depends upon the temperature, and that of ice II probably depends upon its thermal history. The temperature dependence of the rate for ice V, and the history dependence of the rate for ices III and V were not examined. Ice Ic has previously been made only in small quantities; it can now be made in as large quantities as required by transformation of the high-pressure ices. The transformation of ice Ic to ordinary hexagonal ice (ice Ih) has also been examined. The rate depends markedly on the thermal history of the sample and this may help to explain the apparently inconsistent rates that have been reported by various workers.