一个二元体系折光率与组成的关系式

AN EQUATION ABOUT THE RELATIONSHIP BETWEEN COMPOSITION AND REFRACTIVE INDEX OF A BINARY SYSTEM

本文测定了乙醇—水及正丙醇—水体系在20至40℃间的折射率及密度.提出了一个经验公式来描述折射率与二元体系重量组成的关系.公式为γ=AP+BP^(1.2)2+γ_0其中γ=n2-1/d,a 是折射率,d 为同一温度下溶液的密度.γ_0是纯水的γ值.P 是溶液中醇的重量百分含量,A,B 为两个参数.对乙醇—水系 A=(10)/(101),B=1/(44).对正丙醇—水系 A=1/9 B=2/(57)。

Refractive index is one of the parameters which can be used to measure the purity of liquid compoumds conveniently.Refractometry sensors made from optical fiber,which are being developted in laboratories,could be adopted as an on-line monitory technique for the purity of organic chemical production processes or for the measurement of the composition of some binarry liquid systems.There have been many equations about the relationship between the composition of a binary liquid system and the refractive index in the litera- tures. In this paper,refractive index and density of ethyl alcohol water、and n-propylalcohol-water system,the components of which varied from pure al- cohol to pure water have been measured at 20,25,30,35,40℃.An emperical equation γ=A_p+B_p^(1.2)+γ_0 has been proposed to describe the relationship between the refractive index and the cemposition of a binary liquid system at different temperatures.In the equation γ=(n^2-1)/d,is defined as the modified refractive index and r0 is the value of r for pure water,p is the weight fraction of the alcohol in the binary system,and A and B are two parameters.n is refrative index and d is the density of the system at the same temperature,since n and d are both temperature dependent.It results in r which is temperature indepen- dent.That is why the above equation can be used in different temperatures. For the ethyl alcohol-water system A=10/101 and B=1/44,and for the n-propyl alcohol-water system A=1/9 and B=2/57.The equation is simpler than that appeared in the liteatures and fits the experimental results very well.