HCL/CL Method

[Franciz]

Hi all,

I know AR= 1Part Nitric Acid to 3 or 4 parts hydrochloric acid, But what is HCL/Cl?

After reading some of the thread here, If i did not understand wrongly, By using HCL/Cl method can do the same job as AR dissolve gold and precipitate with SMB. But i see the advantage here if we use AR there will be a need to drive off the nitric and if using HCL/CL method we will just need to set it in a open container for 24HR and the Chlorine will be gone by itself without needed to use urea or evaporating off the excess nitric acid.

Can anyone tell me how to do HCL/CL method, The chemical percent and the HCL/CL ratio and also will it take longer time to dissolved gold foils than AR without heat?

Also please can anyone point out the advantage and disadvantage between AR and HCL/CL.

I am interested in this method because i am think if i have material has only gold but less gold in content and the volume of the material is alot then i can use a big bucket of HCL/CL solution and soak all the material in it after gold dissolved, removed and rinses then leave it 24Hr then precipitate with smb :lol: Unlike AR, If material gold content is low and the volume of material is big everytime i got to soak it the material in AR in lots bit by bit because i am afraid if i make too much AR then there will be more free nitric acid for me to get rid off later :lol:

I don think my thinking is all correct but at least i am trying to think and try figuring out every method so i will know what type of method is best for difference type of material :lol: :lol: :lol:

Francis

 

[patnor1011]

You talk about material and high or low gold content. Define material.

 

[eeTHr]

About AR, just incicendly, its better to not pre-mix it in any proportion. Start with the HCl, then add only a small portion of nitric. Warm the solution, and wait until there is no more reaction. If all the gold is not dissolved, only then add a little more nitric. Keep doing that until all the gold is dissolved, and that way you won't end up with too much nitric. If you add a small button of spare gold at that point, wait until there is no more reaction and remove what's left of the button, there will be no excess nitric left. You can weigh the spare button before and after, then subtract it from the resultant gold product, if you are recording yields for the processed material.

If you add the Clorox in the same manner, you won't have to worry about a lot of excess Clorox. Chlorine will evaporate faster than nitirc, though, so most people don't heat it, or only warm it.

Never boil either when processing gold. I have seen boiling AR mentioned when dissolving platinum, but I think it's a matter of opinion and your lab set up.

Note: If the gold "content" of your material is low, then look into the AP (Acid / Peroxide) process for dissolving the base metals away from the material before dissolving the gold, because base metals in a gold solution will usually cause problems when trying to precipitate.

Like Patnor said, much depends on what type of material you are processing.

 

[vegaswinner]

What would you rinse after HCL-CL? Your gold is already dissolved along with any base metals present.

You should look into AP first, then HCL rinse then onto HCL-CL

 

[butcher]

Franciz,

Others may see things different but this is the way I see this.
HCl (hydrochloric acid), with small additions of 3% sodium hypochlorite solution (bleach for washing clothes), (chlorox is a brand here).

HCl/Cl or (HCl/bleach) or (HCl/sodium hypochlorite) this generates chlorine gas in solution, as the bleach is a basic solution the acid reacts with the hypochlorite solution to form chlorine gas, which will dissolve gold into the acidic HCl solution.

I feel HCl/bleach works good, but is not as strong or as fast as the aqua regia (two acids mixed together), at attacking the metals like gold or PGM's, it does not take the higher heat as aqua regia can (without forming salts), but adding some water when heating the HCl/Cl you can reasonably heat it to even dissolve the hard to dissolve PGM's.

The HCl/bleach will also form salts easier than aqua regia will, as long as not evaporated too far as to form gold salts, the HCl/Cl forms salts while still fairly dilute, these do little harm and can be washed from any silver that may also form, or if solution is diluted these stay in solution, these salts are byproducts of some sodium hydroxide in the bleach, and the hydrochloric acid, forming sodium chloride salts (table salt) (NaCl) and some sodium chlorate salts can also form in this reaction.

As you have already stated the chlorine gas (oxidizer) in HCl/Cl is much easier to deal with than the nitric acid (oxidizer in aqua regia),faster less trouble, the chlorine will not stay easily in a warm or hot solution, (cold solutions hold gases easily), the nitric acid in aqua regia needs a much higher temperature to evaporate it off the excess nitric acid (below the boiling point of the solution, so as not to loose values), the nitric acid if dilute must also concentrate before it escapes as NOx gases, (adding HCl that contains water, it must re-concentrate remaining nitric in solution before it converts to NOx gas), this concentrated nitric can also be a problem of boil-overs while eliminating excess nitric from aqua regia if you are not careful, at a certain concentration the solution want to release huge volumes of NOx gas at once, if temperature is lowered at this point it will not boil over, but when solution of aqua regia concentrates a careful watch of process, like small reaction bubbles forming to indicate time to lower heat, or just lower heat when solution concentrates, (boil-overs is also a way to loose gold or values), HCl/Cl you do not have this trouble either.


Aqua regia has advantages of faster and stronger reactions, and if you add nitric in small proportions, you eliminate many of the troubles of using aqua regia, that and Harold's tric of adding gold to help eliminate any excess nitric you may have added, Aqua regia has many disadvantages, especially for those who really have not learned to use it (but have read all about it and think they do because some kid on you tube showed them how), base metals in solution troublesome, overuse of nitric acid troublesome, boil-overs loss of gold in the dirt troubles that make you cry, and others, but all of these problems can be overcome with careful study of this forum and with advise from our wise ole members.

HCl/Bleach works best for gold foils (it will work for heavier solid gold, but heating and dilution can be a balancing act to keep chlorine in solution, and get thicker chunks of gold dissolved without forming a large pot of salt or gassing yourself with chlorine gas).

HCl/Bleach is very good for those learning the recover and refining methods, less chance of screw ups.

Aqua regia is still the best for dissolving larger pieces of gold or karat gold in my opinion as long as you learn the tricks of the trade.

 

[NobleMetalWorks]

There is no one process that is best for all things. Some processes are better for some types of materials, than others. What you might want to do is post what type of material you are recovering precious metals from, then ask these questions.

What is the best way to FIRST recover the gold and other PMs from the material you are using.

What is the best process, for REFINING the gold, and dropping the other PMs, base and special metals out of solution

For some things you might want to go strait to AR, but that should be your very last option as AR is intended to refine gold, and should really only be used to recover gold if you have no other option.

Recovering gold/PMs means stripping it from all other material, and dissolving as much base metals as possible so that the majority of what is left are the PMs you are going for. Like stripping gold foils from finger boards.

Refining gold is the process of purifying and further stripping other PMs from the gold, or in the case of other PMs, dropping them out of solution and purifying them.

So really there are two different processes, and you should mach them both to the material you are getting them from, what you are comfortable with, and any other considerations like time, money, effort, etc.

You might want to read about the different processes, then you will be better equipped to ask the right questions. And if you haven't already read Hoke, you might want to do that also.