sodium sulfate

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A white crystalline compound, Na₂SO₄, used in the manufacture paper, glass, dyes, and pharmaceuticals. It is often used in its decahydrate form, which is also known as Glauber's salt.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun inorganic chemistry The sodium salt of sulfuric acid, Na2SO4; it is a mild laxative (as Glauber's salt), and is used in the manufacture of paper, detergents and many other products.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a solid white bitter salt used in manufacturing glass and paper and dyes and pharmaceuticals