What is the full form of "AS"?

Ammonium sulfate is an inorganic sulfate salt obtained by reaction of sulfuric acid with two equivalents of ammonia. A high-melting (decomposes above 280?) white solid which is very soluble in water (70.6 g/100 g water at 0?; 103.8 g/100 g water at 100?), it is widely used as a fertilizer for alkaline soils.