ammonium sulfate
n.
A brownish-gray to white crystalline salt, (NH₄)₂SO₄, used in fertilizers and water purification.

---

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

---