device used to measure the salinity of a solution. It is frequently a hydrometer that is specially calibrated to read out the percentage of salt in a solution.

Because the concentration of chloride has been shown to be directly related to the salinity of seawater, titration of chloride with silver nitrate is widely used in oceanography to measure salinity. The International Council for the Exploration of the Sea in 1937 established for worldwide comparison a standard for seawater of 19.381 parts of chlorine per 1,000 parts of seawater.