How much oxidizer or bleach to use, I do not go by a recipe, but you can find one on the forum, sorry I cannot answer what is recommended, but maybe this can help.
Let’s look at how we dissolve gold.
Nitric acid HNO3 will not dissolve gold alone.
Hydrochloric acid HCl will not dissolve gold.
(Actually nitric acid will oxidize the gold at is surface to Au3+).
If we add HNO3 and HCl, then we can dissolve gold into gold ions (the strong acid taking electrons from the gold atoms) to make a solution of gold chloride in this highly acidic state as Chloroauurate acid HAuCl4.
the strong oxidizing reaction of the nitric acid forming AU3+ ions, and HCl with this reacting to form chloroaurate ions (AuCl4) (water soluble gold chloride salts), as atoms of gold from the surface lose electrons and dissolve into solution more gold atoms are exposed to these acids and oxidizers to react, and to dissolve more gold into solution.
A common equation for this reaction:
Au + 3NO3 + 6H --> Au3+ + 3NO2 + 3H2O
Au3+ + 4Cl --> AuCl4
Nitric oxide can also form in this reaction the chemistry involved is actually much more complicated than the equation above represents.
When we mix these two strong acids there are several reactions going on in solution (even more when metals are involved),
Mixing concentrated HCl and HNO3 it also produces volatile gases in solution, these gases will also react with our metals (these gases do not stay in solution long, that is why we cannot premix and store our Aqua regia to use later, the active ingredients like the gases can leave the solution leaving us with a strong acid that without these gases would not dissolve gold that well)
NOCl nitrosylchloride gas and Cl2 chlorine gas are two of these volatile gases that will also react in our aqua regia solution to help dissolve gold or platinum.
3HCl + HNO3 --> NOCl + Cl2
NOCL can decompose further to form more chlorine and nitrous oxide gases.
2NOCl --> Cl2 + NO
Nitrous oxide reacting with air above our vessel can give us the red fumes we see as NO2 gas
NO + O2 --> NO2
2
3HCl + HNO3 --> NOCl + CL2 + 2H2O
How much oxidizer do we need? Much depends on how you perform the reaction, if your solution was dilute (gases will not escape as easily and can mix with water to reform acids), or if your solution was cold (cold solutions can hold more gases), what all metals you have in solution can also make a big difference as metals lower in series would react differently than the more noble metals, so as you can see saying you need this much oxidizer as nitric acid with this much HCl, would not always be true if you used or ran your reaction different or under different conditions.
It is good to have a little excess HCL, and to keep the solution acidic, the oxidizer (nitric acid or bleach) can be added in small increments only using the amount needed to dissolve the gold.
Now let’s look at dissolving gold with NaClO bleach or sodium hypochlorite and HCl hydrochloric acid.
Some things we should consider 5% NaClO has 95% water, it will also be basic solution containing NaOH sodium hydroxide (to keep chlorine in the in solution), so not only will adding bleach dilute our acid but it will also form salts out of our acid (neutralizing the HCl to table salt) reducing our acids effectiveness to dissolve more gold into solution.
2HCl + NaClO --> NaCl + Cl2 + H2O
2Au + 3Cl2 --> 2AuCl3
2Au + 3Cl2 + 2HCl --> 2HAuCl4
HCl + NaOH --> NaCl + H2O
2HCl +NaClO + 2HCl --> 2NaCl + Cl2 + H2O
Cl2 +H2O --> H + Cl- + HCLO
HCLO --> H + ClO
Cl2 +Cl- --> CL3
Au + Cl- + 3/2Cl2 --> AuCl4
Here again temperature of the solution will also determine how much chlorine we generate and how long it will stay in solution, as well as the solutions concentration, adding bleach not only dilutes our solution more it also neutralizes the acid in solution (needed to generate chlorine) which will also affect how much gold can be dissolved, also the metal involved if fine powder or very thin such as you will find on plated glassware or the thicker gold foils from memory can also determine how much of the reacting acid and bleach we would need to get our gold dissolved, how easily it will dissolve, or how much gases will be formed from the reaction.
When I add sodium hypochlorite to hydrochloric acid to dissolve gold, I do not go by a recipe, but I do add small portions to create chlorine in the acidic solution let it react, and add more later as needed (sometimes I do the opposite having gold in a bleach solution and add portions of HCl acid to dissolve the gold), I also use heat to help speed the reaction (more chlorine gases form but also more unreacted gases leave the solution more hypochlorite needed, and also creates more salts in solution and neutralizes more acid), or give the reactions more time and dissolve the gold in a cooler condition where it takes longer but uses less bleach and less acid.
over use of bleach is generating chlorine gas that gases off without doing any work to dissolve metals like gold or platinum, it dilutes the solution with water and neutralizes more acid (making the solution less effective at dissolving metals), and creates more salts out of your acid, and if too much bleach is added when you need to rid the oxidizer, heating can create more salts that as the salt solution drives off the chlorine and water.
After we use an oxidizer to dissolve the gold or form gold chloride the oxidizer needs removed from the gold chloride for us to be able to precipitate or gold from solution, or to reduce the gold back to metal powders (reduction is to give the gold atoms back electrons), in another chemical reaction, so using too much oxidizer can also make it a little more difficult when we wish to precipitate the gold, when using nitric acid this is more of a problem, so using only the amount of nitric needed becomes important, if you do not wish to spend many hours evaporating solutions, or adding another contaminate to your gold solution, chlorine in solution from using sodium hypochlorite as an oxidizer is much easier to remove as the chlorine gas will not stay long in a hot solution,
How much bleach to add?
Much depends on how you drive the reaction.
But to get an idea of how much you may need to begin with, read the general reaction list provided on the forum, I believe a recommended recipe is there.
