Salinity is the degree of saltiness, as of the oceans. The average proportion of salt in the sea is about 35 parts 1,000 (3.5%). In the red Sea, because of high evaporation rates, the figure is over 40, but in the northern parts of the Baltic Sea it is less than 10, and in the Dead Sea the figure is about 250. The salts found in the oceans include sodium chloride (common salt), which accounts for about 75%, magnesium chloride, magnesium sulfate, and calcium sulfate.