Chemical Reaction Aqua Regia for Gold

        Aqua regia or in Latin is more known as royal water is a chemical solvent all the metals, where the solution is the result of mixing a solution of hydrochloric acid (HCl) and a solution of aqua fortis or more in the know with Nitric Acid (HNO3), which is part of an oxidant the most powerful. In a mixing between hydrochloric acid (HCl) and Nitric Acid (HNO3) is 3: 1, That is the volume of a solution of 3 parts hydrochloric acid (HCl) was added to 1 volume part of the solution of Nitric Acid (HNO3)      
        In practice Aqua regia is often used as a solvent in the processing of gold metal, and chemicals are often used as a gold refiner. The process is very simple dissolution happens when metal reacts gold by aqua regia solution.

Chemical reactions

Au + 3HNO3 + 4HCl HAuCl4 + 3NO2 + 3H2 O
Au (s) + 3 NO3-(aq) + 6 H + (aq) Au3 + (aq) + 3 NO2 (g) + 3 H2O (l) and
Au3 + (aq) + 4 Cl-(aq) AuCl4-(aq).


 After the reaction is complete then the next step is the process of settling and separation of the deposition solution. The next solution in neutral with the addition of urea to reduce the residual HNO3 As happened in the following chemical reaction

6 HNO3 + 5CO (NH2) 2 = 8N2 + 5CO2 + 13H2O
And gold gained by cementation, ie precipitation with the addition of sodium metabisulfide, as in the following reaction:

2HAuCl 4 + 2NaHSO3 = 2Au + 4HCl + Na2 SO4 + SO2
or with the addition of hydrogen peroxide (H2O2) and Sodium Hydroxide (NaOH). Further sediment left in the wash with hot water and then dried in the melt to be made in a metal