Refractometry
Absolute Specific Gravity:
The ratio of the weight of a given volume of a substance in a vacuum at a given temperature to the weight of an equal volume of water in a vacuum at a given temperature.
Specific Gravity:
The ratio of the mass of a body to the mass of an equal
volume of water at 4°C
or other specified temperature. Dimensions, unity.
Density:
Concentration of matter, measured by the mass per unit volume. Dimensions, (ml^{3}).
