介绍了一种基于双液芯柱透镜(DLCL)测量液相扩散系数的方法-等观察高度测量法,该方法利用双液芯柱透镜的前液芯作为扩散池和主要成像元件,后液芯作为辅助消球差元件。选择双液芯柱透镜上某一固定高度作为观测位置,根据观测位置处扩散图像宽度随时间的变化规律,基于Fick第二定律计算液相扩散系数。用等观察高度测量法测得室温(25 ℃)下0.33 mol/L氯化钾水溶液的扩散系数D=1.8530×10 ^-5 cm ²/s,测量结果与文献值之间的相对误差为0.65%。该方法利用双液芯柱透镜在一定折射率范围内减小球差的优势,使得测量液相扩散系数具有精度高(相对误差小于1%)、速度快(测量时间约为60 min)和扩散过程可视化的特点。

A method to measure liquid diffusion coefficients based on double liquid-core cylindrical lens (DLCL): equivalent observation altitude measurement method is introduced. The front liquid core of DLCL is used as both diffusive pool and main imaging element, and the rear liquid core is used as aplanatic auxiliary element. A fixed altitude of DLCL is selected as observation position. Based on the Fick’s second law, the liquid diffusion coefficient is calculated according to the relationship between the diffusion image width and time. The diffusion coefficient of 0.33 mol/L KCl aqueous solution is D=1.8530×10 -5 cm 2/s, which is measured at the room temperature (25 ℃) and by equivalent observation altitude measurement method. The relative error between the measured results and the literature values is 0.65%. The proposed method makes use of the advantage of DLCL that can reduce the spherical aberration in certain range of refractive index, which makes the liquid diffusion coefficients have the characteristics of high accuracy (relative error is less than 1%), high speed (measurement time is about 60 min), and the visualization of diffusion process.