改进的凝固点降低法测定摩尔质量实验装置

An Improved Device for the Experiment of Determining Molar Mass with Freezing Point Depression

介绍一个改进的凝固点下降法测定摩尔质量实验装置，它由保温瓶、凝固点杯、贝克曼温度计、电动搅拌器等几部分构成。实验时，先调节寒剂的组成使其凝固点低于待测溶液的凝固点～2℃，然后分别在保温瓶和凝固点杯中加入寒剂和待测溶液的冰水，启动搅拌器预冷却2～3小时，接着更换保温瓶中的寒剂冰水，重新启动搅拌器，记录贝克曼温度计读数。实验结果显示，改进的凝固点降低法测定摩尔质量实验装置结构合理，其测定误差可控制在±0．001℃以内。

A device for determining molar mass with freezing point depression was improved, which consists of the Dewar bottle, sample container, Beckmann thermometer, and motor stirrer. Before the experiment, the freezing point of the coolant was controlled about 2 ℃ below the freezing point of the sample solution by adjusting the composition of the coolant. The ice/ liquid mixtures of the coolant and the sample solution were respectively added in the Dewar bottle and the sample container to precool for 2 - 3 hours under stirring. Then some of the coolant liquid was replaced with coolant ice, the motor stirrer was restarted, and the temperatures were read from the Beckmann thermometer. The results show that the structure of the improved device is rational, and its measuring error for the freezing point of sample solution can be controlled between ± 0.001 ℃.