Everything as follows: I'm looking to calculate the amount of NaCl (rho=2.19 g/cm^3) needed to add to water (rho=0.999 g/cm^3) to achieve a solution with density=1.071 g/cm^3. Ideally, I want to achieve an Atwood Number of 0.035 and a density of 1.071 g/cm^3 is what I need for the solution. However, the problem is that I'm not sure as to the exact concentration of salt that I need to have in the solution. I measured the density of the solution with 3 g/liter NaCl, 6, 10, 20, 30, 50, 70, 100, 150, and 190 g/liter NaCl. The 100 g/liter NaCl gave me a density of 1.067 which is far off since I need to achieve an Atwood number of 0.035 (extremely small number so even smaller room for error). I'm sick of the trial and error method to achieve a solution density of 1.071 g/cm^3, is there any mathematical way I can go about figuring out the exact amount of salt I need? (theoretically at least, I will still measure the density) Equations Atwood number =[ rho(saltwater) - rho(water) ] / [ rho(saltwater) + rho(water) ] Atwood number is a dimensionless number used in fluid dynamics to relate the densities of two fluids. It can help to predict what instabilities will be present in a flow.