From the refractive index, the density can be determnined with the following formula:
with = density at 25 °C and = refractive index .
a and b are constants that depend on the salt used to establish gradient solutions. Some common salts and their coeffcients are shown below.
|Cs acetate||10.7527||13.4247||1.80-2.05 g/ml|
2. Place the drop on the cleaned prism top. Cover and observe through the eye piece. With the dial, move the border between dark and light so that it crosses the cross right in the centre, as shown here. Then take the reading on the upper scale; you should estimate the last digit. This will give the refractive index of KBr solution. In this example, the refractive index is 1.3353
3. Use the appropriate values and the formula given in the following table to calculate the respective densities.