Baking Soda

[plasmabrain]

Can I use baking soda to neutralize poor mans AR or do I need to use urea to take care of the nitrate?

 

[butcher]

Baking soda would neutralize all acid, including the HCl, so if you had gold, and most of the other metals in solution it would precipitate if you neutralized the acid.
if this was your goal you could add any base to destroy your acid, that is not what we want to do, we want to keep the gold in a acidic chloride, but eliminate the Oxidizer (nitric acid in this case).

How much base (baking soda) you added would determine the PH (percent hydrogen) of your solution, once you get close to PH 7 you no longer have acid but a salt water solution.

Urea would remove any nitric that has not reacted, but here you are adding more contaminates to your solution. my opinion not a good idea, these chemical reactions are hard enough to accomplish, adding Urea is just adding to your problems later in the chemical reactions, I feel taking shortcuts just give you a longer road to travel later.

I would look at using minimum nitric, (nitrates with your acid here in your case) slow evaporation to remove excess nitric, and Harold's trick addition of gold to eliminate nitric.

With poor mans, to help keep nitrate down to minimum you could heat your acid and add nitrates a little at time, keep heating and let reaction complete using up the formed nitric in solution, if solution was concentrated heating would also drive off NOXX gases as the metals in solution dissolved, with care you would not have much nitric to eliminate at the end of your process.

I edited to try and make this readable.

 

[plasmabrain]

Thanks, that all sounds pretty solid to me. Also after doing some more reading I was considering just diluting with 3x water and trying that. The reason I asked this question in the first place is I processed some e-scrap and I used baking soda to neutralize. When I sent it to ARA they said it had no value, so I was wondering if the baking soda screwed up my precipitation some how.

 

[Oz]

Diluting a problem often just results in a more volumous problem (there are situations that dilution helps).The first thing you must know before shipping anything to any refinery is exactly what you are sending. If you do not know what you have refined or the purity, you do not have a clue if you were paid properly. They may be honest or dishonest as to what you sent. You will never know either way if you do not take the time to learn to refine properly and test your results.

 

[plasmabrain]

So Harold's trick is basically saying is that once you stop dissolving gold, all your nitrate or nitric has been used up, is that correct?

 

[Harold_V]

So Harold's trick is basically saying is that once you stop dissolving gold, all your nitrate or nitric has been used up, is that correct?

It means that you have consumed one of the two acids, and nothing more. To insure that you have consumed all of the nitric, there should be too much HCl present, along with some free gold.

If you used anything to neutralize acids, it's entirely possible you shifted pH to the point where you precipitated the values. If that's the case, they'd be found mixed in the solids that were filtered from the solution.

I have one question for you.

Why are you trying to reinvent the wheel?

There's no shortage of published methods to accomplish the desired end. I never recommend you ignore them unless you understand refining very well, and have a good reason from deviating from what is known to work.

Read Hoke.

Harold

 

[plasmabrain]

I wasn't trying to reinvent anything, I was ignorant of the point of adding urea in the first place, so I thought any basic chemical was needed to neutralize my acid, I didn't realize the whole point was to remove the oxidizer from solution. Now I know the point.

 

[gold4mike]

I'm glad I bumped into this thread. I have been using Harold's tip, putting a small gold button in my AR solution to use up the remaining nitric. I assumed that, when there was no more reaction, all the nitric was used up.

Harold's response in this thread, that it could also mean that all the HCl is used up and there is still a possibility of some nitric, has convinced me to add a little HCl once the reaction has stopped.

If no reaction commences I can safely assume that I have finally exhausted the nitric.

I learned something new again today!

 

[Harold_V]

Harold's response in this thread, that it could also mean that all the HCl is used up and there is still a possibility of some nitric, has convinced me to add a little HCl once the reaction has stopped.

You may recall that I evaporated all of my solutions, if for no other reason, to condense them to smaller volumes. In the process, especially if the solution had come from digesting filings from the jeweler's bench, where it's not clear when all of the gold has been dissolved, I'd use an excess of nitric intentionally. That guaranteed the customer was not short changed, but left me with a solution that had too much nitric on occasion. In spite of what you may read, in practice, evaporating the nitric isn't as easy as they'd have you believe it is. On many occasions I'd have the solution down to a dark red color, at which time I'd add more HCl. If there was free nitric present, the reaction was instantaneous and sure---brown fumes evolved readily, and bubbling would occur on the added gold. I'd repeat this process until there was no reaction upon adding more HCl.

So then, yes, you must add free HCl to insure that you have exhausted nitric---it can remain unnoticed, otherwise. I thought I'd made that clear in earlier posts, but it, hopefully, is clear now.

Harold

 

[Harold_V]

I wasn't trying to reinvent anything, I was ignorant of the point of adding urea in the first place, so I thought any basic chemical was needed to neutralize my acid, I didn't realize the whole point was to remove the oxidizer from solution. Now I know the point.

Read Hoke. (Keep in mind, she does not discuss the use of urea, and I don't recommend its use.)

Harold