Simplify the following text for a Grade 13 native English-speaking person.
Original: Currently , it is produced by heating a mixture of ammonium chloride , or ammonium sulfate and chalk , to redness in iron retorts , the vapors being condensed in leaden receivers . The crude product is refined by sublimation , when it is obtained as a white fibrous mass , which consists of a mixture of ammonium bicarbonate , NH4HCO3 , and ammonium carbonate , ( NH4 ) 2CO3 , in molecular proportions ; on account of its possessing this constitution it is sometimes called ammonium polycarbonate .
Simplified: Ammonium carbonate is made by reacting ammonium sulfate , ammonium chloride , and calcium carbonate in a furnace .