本文介绍了一种利用激光测量透明液体浓度的实验装置，该装置通过转动环形电阻来精确测量所转过的角度，利用光敏电阻的阻值大小变化准确判断激光穿过三棱柱后发生全反射时的入射临界角位置，求出液体的折射率，再通过折射率与浓度之间的线性关系测量出液体的浓度.该装置能测量透明葡萄糖、氯化钠、蔗糖和甘油等有机溶液以及无机溶液的浓度，具有普适性.同时还可用于中学、大学科普演示或课堂教学，增强学生对于全反射知识的理解与掌握. 

This article introduces an experimental device for measuring the concentration of transparent liquid by laser. The device accurately measures the angle of rotation by rotating the ring resistor, accurately judges the critical angle of incident when the laser passes through the triprism and the total reflection occurs by the change of the resistance value of the photoresistor, and obtains the refractive index of the liquid. Then the concentration of liquid is measured by the linear relationship between refractive index and concentration. The device can measure the concentration of organic and inorganic solutions such as transparent glucose, sodium chloride, sucrose and glycerol, and has universal applicability. At the same time, it can also be used in middle school, university science demonstration or classroom teaching to enhance students’ understanding and mastery of total reflection knowledge.