Sodium metal is the 4th most abundant element on earth. It is obtained commercially by the electrolysis of absolutely dry fused sodium chloride. The most common composition is sodium chloride (table salt) but it occurs in many other minerals, such as soda niter and amphibole. Metallic sodium is vital in the manufacture of esters and in the preparation of organic compounds. The metal may be used to improve the structure of certain alloys and [purify molten metals. An alloy of sodium with potassium, NaK, is an important heat transfer agent. The average cost of sodium metal is $0.75 per gram.