What works slow?

[bswartzwelder]

From reading Hoke, I have learned that if you use more than what you need of certain chemicals (such as a quart of AR for an ounce of gold), you will normally achieve what you are trying to do much faster. "Fresh acids work more rapidly than those that are partially exhausted." She also states that "If you use much water you increase your acid efficiency but decrease the speed of operation." Using an overabundance of chemicals usually means you will produce more waste which will have to be dealt with at some time.

AP works very slowly, but does not normally dissolve gold. AR should not be mixed in advance because it cannot be easily stored for long periods of time. Acid/Chlorox works well, but like AR, it's "staying power" is limited. I believe Patnor uses the term "deathable" when talking about tin chloride testing solutions, and it seems appropriate here as well.

If you are not in any hurry, is there any solution whereby you could drop some larger pieces of gold into it and just leave it? Perhaps come back to it in a week or two and have the gold dissolved. I have not seen this particular question addressed previously. Usually newcomers want to get their gold as quickly as possible. THANK YOU in advance for any comments.

 

[Geo]

AP works much faster when heated. ive cut a plastic drum the height of a five gallon bucket and use water and a small 110v drop in water heater to heat the solution. it works great and cuts the reaction time as much as half.

 

[butcher]

Is there any solution whereby you could drop some larger pieces of gold into it and just leave it? Perhaps come back to it in a week or two and have the gold dissolved.

In these reactions the gases created in solution oxidize the gold, once these gases are created, in aqua regia for example, they will begin the oxidation process taking electrons from the gold atoms forming gold ions which make a gold salt with the chlorides in solution, as soon as the chemicals are mixed like HCl and HNO3 in this case these gases begin to form and can begin to evolve from solution with or without gold in solution, as we know temperature, pressure, dilution, whether there are metals to react with, how reactive the metals are to the gases formed, surface area, passivisation of the metals, whether metal will even react in solution, how noble the metal, and what metals are amalgamated and there percentages, and many other factors will decide how slow or fast, and even if these gases will react with the metal before they leave the solution, or if the gases can be held in solution long enough to oxidize the gold, diluting, chilling, working under pressure the aqua regia with large thick bar of pure gold, you could keep the gases in solution for a long period, and take months to dissolve the gold (which would hold gases in solution better as the gold dissolved), on the other hand we can use heat and and fine gold powder and put the gold in solution in a fairly fast amount of time with loss of more gases wasted in the heat of the reaction.

So in essence it is possible to make up a solution or apparatus that would create the gases needed and hold them in solution longer and have our gold in a form that could take a month to dissolve it.

Are there other chemicals that will dissolve gold, yes, and would these other chemical have conditions which would determine how fast or even if they would put gold into solution, yes, could we change our conditions to determine how fast or even if we will put gold into solution, yes.

Bert,
you ask what works slow, well in the question you actually gave the answer, cold dilute acids, metals in a condition or form which would be attacked slowly, in a solution which oxidized the gold slowly retaining the needed gases or acids to do the work.

 

[bswartzwelder]

I was aware that keeping pressure on a reaction vessel would slow it down and allow it to work longer before it died. I also knew that dilution would slow things down and heat would speed them up.

I was hoping there was another chemical process (other than cyanide or mercury) that might be substituted for the AR or acid/Chlorox. As per Ms. Hoke, I was looking for efficiency rather than speed. I have to admit, I hadn't thought of an aquarium heater to speed up AP, but that's another process where I can dump everything in and wait. My last batch of foils sat in the AP for about 2 or so months. (I can be very patient.)