This is the general term for water from the sea or ocean. Typical seawater has a dissolved solids concentration, or salinity, of approximately 35,000 milligrams per liter (mg/L). Seawater is a chemically complex substance that may contain more than 70 chemical elements. Most elements are present only in minor, or trace, concentrations, while more than 99 percent of the dissolved solids consist of 6 constituents: Sodium (11,035 mg/L), Chloride (19,480 mg/L), Magnesium (1,330 mg/L), Sulfate (2,770 mg/L), Calcium (420 mg/L), and Potassium (400 mg/L).