1. The problem statement, all variables and given/known data Is there any way to calculate a solution's concentration (mass percentage - that is, the percentage of the solute mass to the solution mass) just by knowing its index of refraction? If it helps, the solute is NaCl, so I know the molar mass of the solute. I also have the solution's mass, the solution's volume, and, by calculation, the solution's density. 2. Relevant equations None that I know of... 3. The attempt at a solution In the beginning, I tried to establish a relationship between a solution's index of refraction and its density experimentally (i.e. making a table of solutions with different densities and their corresponding indexes of refraction to extrapolate some kind of equation to relate them) and then find a relationship between its density and its concentration, but this method has the potential to be extremely inaccurate and may not even work at all (if the index of refraction - density table cannot determine a relationship between index of refraction and density). I'm hoping there is some kind of equation or experimental method more practical/accurate than the one I came up with to figure this out. Thanks in advance!!!