<Dl> <Dd> Au + HNO 3 + 4 HCl ↽ − ⇀ (\ displaystyle (\ ce (<=>>))) (AuCl 4) − + (NO) + (H 3O) + + H 2O </Dd> </Dl> <Dd> Au + HNO 3 + 4 HCl ↽ − ⇀ (\ displaystyle (\ ce (<=>>))) (AuCl 4) − + (NO) + (H 3O) + + H 2O </Dd> <P> If the aqua regia solution only contains gold, solid tetrachloroauric acid may be prepared by boiling off excess aqua regia, and removing residual nitric acid by repeatedly heating with hydrochloric acid . That step reduces nitric acid (see decomposition of aqua regia). If elemental gold is desired, it may be selectively reduced with sulfur dioxide, hydrazine, oxalic acid, etc . Appropriate equations are, for example: </P> <Dl> <Dd> 2 AuCl − 4 + 3 SO 2 + 6 H 2O → 2 Au + 12 H + + 3 SO 2 − 4 + 8 Cl − . </Dd> </Dl>

What is the chemical name of aqua regia