重铬酸钾水溶液低温热容的研究

Investigation of Low Temperature Heat Capacities of Aqueous K_2Cr_2O_7 Solution

用低温绝热量热法精密测定了重铬酸钾水溶液在 80～ 3 70 K温区的摩尔热容 Cp,m、凝固点、摩尔熔化焓和熔化熵 .T≤ 2 65 K体系为固相 ,Cp ,m与 T成线形关系 ;2 65 K<T<2 75 K体系发生相变 ,由固相转化为液相 ;2 75 K≤ T≤ 3 70 K该水溶液的热容基本不变 .该水溶液的凝固点为 2 72 .5 2 K,摩尔熔化焓和熔化熵分别为 6.0 85 k J/mol和 2 2 .3 3 J/(K· mol) .根据所测热容及相关的热力学关系式 ,计算了以 2 98.1 5

In order to investigated the mechanism of heat transition of aqueous potassium dichromate solution as working fluid in heat pipe,the molar heat capacities of potassium dichromate solution ( C p,m )were measured by a low temperature adiabatic calorimeter over the range from 80～370K.No thermal anomaly was observed in the range from 80～265K.The functions of C p,m vs. T were established based on the measured heat capacity data by using the least square fitting method.The freezing point,molar freezing enthalpy and freezing entropy of the solution were established to be 272.52K, 6.085kJ/mol and 22.33J/(K·mol),respectively.The heat capacities of the solution are near a constant in the range 275K≤ T ≤370K.According to the relationship of thermodynamic functions,the thermodynamic function values of the solution were calculated in the temperature range of 275～370K with 5K intervals.