Sodium is the sixth most abundant element in Earth’s crust, and it occurs naturally as a component of many salt and alkaline lakes. Economic reserves of natural sodium sulfate are estimated at about 3.3 billion tons worldwide. World production averages up to 2.6 million tons per year, and supplies will be adequate for many centuries.
Various forms of sodium sulfate are produced by the chemical industry. The most common is anhydrous sodium sulfate, and it is used in detergents and for forming the cooking agent in Kraft paper pulp.
There are also decahydrate and heptahydrate forms of sodium sulfate. Decahydrate is more common in the pharmaceutical industry and it is used to produce synthetic sulfate ions.
It is also a major raw material in the chemical industry for the production of sodium sulfide and sodium silicate. It is used as a drying agent in organic synthesis and is also a filler in synthetic detergents.
Synthetic sulfate is made by a series of reactions. One of the most widely used is the Mannheim process, which produces sodium sulfate by reacting sodium chloride with sulfuric acid. Another method is the Hargreaves process, which produces sodium sulfate from sulfur dioxide and water.
Sodium sulfate is soluble in water, but its solubility increases dramatically with temperature. Its solubility rises more than tenfold between 0 degrees Celsius and 32.4 degC, reaching a maximum of 49.7 g of Na2SO4 per 100 g of water at 32.4 degrees Celsius. This is because the ionic form of sodium sulfate completely dissociates into sodium and sulfate ions when it comes into contact with water.