Refractive index is one of well-known analytical technique to identify a liquid compound, and it was successfully measured using a laser pointer and a chromatography column with high accuracy. We expanded the system to binary organic liquid mixtures and found that there was a good relationship between the refractive index and various types of concentration such as %volume, %mass, molarity and density. This system could be used not only for the qualitative analysis, but also for the quantitative analysis.