Determination of Concentration of NaCl Solution within its Saturation Limit using Refractive Index Method

At room temperature NaCl solution of one to five molal concentration was prepared separately. Refractive index of each molal concentration of NaCl solution was obtained using Spectrometer and hollow glass prism. By using Shuster method and Sodium source as a monochromatic light source it was verified with that refractive index of solution was found to be increased with increase in molal concentration of solution. Graph of refractive index of medium against molal concentration showed linear relationship. Another unknown molal concentration of NaCl solution within saturation limit was prepared. Refractive index of that unknown concentration of NaCl solution was 1.3642. The obtained value of refractive index of medium was used to determine concentration of the solution by help of graph and was founded to be approximately 4 molal concentration.