Aqua regia A mixture of one part by volume of concentrated nitric acid and three parts of concentrated hydrochloric acid. Aqua regia was so named by the alchemists because of its ability to dissolve platinum and gold. Either acid alone will not dissolve these noble metals.
Antimony A chemical element, symbol Sb, atomic number 51. Antimony is not a naturally abundant element; it is occasionally found native, often in isomorphous mixture with arsenic, as allemonite. The symbol Sb is derived from the Latin name stibium. The element is dimorphic, existing as a yellow, metastable form composed of Sb4 molecules, as in
Ammonium salt A product of a reaction between ammonia, NH3, and various acids. The general reaction for formation is NH3 + HX –+ NH2X. Examples of ammonium salts are ammonium chloride, NH4Cl, ammonium nitrate, NH4NO3, These compounds are addition products of ammonia and the acid. For this reason, their formulas are sometimes written as [H(NH3)]X.