ammonium chloride

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

• noun A slightly hygroscopic, white crystalline compound, NH₄Cl, used in dry cells, as a soldering flux, and as an expectorant.

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

• noun inorganic chemistry A water-soluble salt of ammonia and hydrochloric acid, having the formula NH4Cl.

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

• noun a white salt used in dry cells