## Temperature Compensation Method to Solve the Fractionation Effect in the Experiment of Binary Vapor-Liquid Equilibrium System Phase Diagram

Song Liping, Wang Yating, Zheng Ou,, Wu Shuting, Zhu Shuying, Chen Jianzhong

 基金资助: 国家自然科学基金项目.  21775026福州大学一流本科教育改革项目.  003698福州大学本科生科研训练项目.  25071

 Fund supported: 国家自然科学基金项目.  21775026福州大学一流本科教育改革项目.  003698福州大学本科生科研训练项目.  25071

Abstract

In this paper, the device for phase diagram development experiment has been modified, which can be used to measure the boiling point and dew point of vapor-liquid equilibrium system simultaneously. In addition, the vapor-liquid phase diagrams of cyclohexane-ethanol under the conditions of no heat preservation, heat preservation and temperature compensation are drawn and compared. Results show that there is a great difference between the temperatures of boiling point and dew point both for the vapor-liquid equilibrium system with the simple heat preservation or without the heat preservation, and the vapor-phase lines based on the boiling point temperature are seriously distorted. With the temperature compensation for the system, the two vapor-phase lines according to the boiling point and the dew point temperature are in good agreement, which means the problem of vapor-phase fractionation effect has been solved.

Keywords： Physical chemistry ; Vapor-liquid phase diagram drawing ; Fractionation effect ; Temperature compensation

Song Liping. Temperature Compensation Method to Solve the Fractionation Effect in the Experiment of Binary Vapor-Liquid Equilibrium System Phase Diagram. University Chemistry[J], 2020, 35(1): 87-91 doi:10.3866/PKU.DXHX201905002

“双液系气液平衡相图”实验项目是物理化学实验课程中的一个重要的基础实验[1-10]。目前，该实验项目国内各高校常用的设备是内置加热式沸点仪，并可通过沸点法绘制相图[2-6]，其优点是操作简单、减少爆沸且系统受热均匀。但由于气相分馏效应的存在[2, 3, 11]，获得准确的双液系相图并不容易[8-10]。前期实验工作观察发现，若不采取保温措施，纯的乙醇气液系统平衡时蒸馏瓶内气相的温度分布存在一定的梯度[11]，造成了气相的分馏效应；利用保温隔热套加速了系统建立气液平衡，减少蒸馏瓶内气相的温度分布梯度，一定程度上降低了气相的分馏效应，但未真正解决沸点和露点温度是否一致的问题，因此不能判断沸点法绘制的相图是否准确。

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