Will hot HCL act like Nitric?

[Brett Novak]

Sorry if that's a stupid way to say it. On occasion I am having a helluva time dropping gold with SMB out of AR. Now I do use the "drip" method of adding nitric instead of just aiming for 3:1 to reduce the amount I'm using. But.... even if I let it evap on low heat overnight, reactions have stopped, when I hit it with SMB it goes foam party crazy. Gold never drops, instead I get a layer of SMB solids on the bottom.

If I hit it with Urea, nothing happens either....

Solution temperature is around ambient, 100 to 105*F / 37*C - I'm just wondering, maybe the high ambient temp is the issue?

Maybe just add more water and dilute it as much as possible? (Not sure if there is a point where the gold will start dropping if the dilution becomes too high?)

cheers and thanks in advance....maybe there's a neat trick someone can share that can make an easy test for Nitric remaining in the AR?

 

[Martijn]

Could be. Have you tried dropping it colder? I do it right after chilling and filtering. No patience is the main cause

 

[Shark]

After you evaporate the solution, did you add more hydrochloric acid? HCl is a gas dissolved in water, by heating, especially high heat, will force the gas out of the water. A PH test might give some surprising answers.

I usually drop from a hot solution on my second refine, usually no problem. Quite often I will drop hot from both rounds. I just heat my precipitant at the same time I heat my solution. Then you need head space in case it boils over, but after a few times it gets easier to “see” potential problems ahead of time.

 

[Yggdrasil]

Sorry if that's a stupid way to say it. On occasion I am having a helluva time dropping gold with SMB out of AR. Now I do use the "drip" method of adding nitric instead of just aiming for 3:1 to reduce the amount I'm using. But.... even if I let it evap on low heat overnight, reactions have stopped, when I hit it with SMB it goes foam party crazy. Gold never drops, instead I get a layer of SMB solids on the bottom.

If I hit it with Urea, nothing happens either....

Solution temperature is around ambient, 100 to 105*F / 37*C - I'm just wondering, maybe the high ambient temp is the issue?

Maybe just add more water and dilute it as much as possible? (Not sure if there is a point where the gold will start dropping if the dilution becomes too high?)

cheers and thanks in advance....maybe there's a neat trick someone can share that can make an easy test for Nitric remaining in the AR?

You say boiling, do you boil it to almost dry?

 

[Brett Novak]

Yes - evaporating it to dry (over the course of about 8 hours) then adding HCL and I end up with a thick mudlike goop.

Shark - I never thought about pre-heating the SMB (I usually use powder, I guess I can try disoolving it first, or try FeSO

 

[lazersteve]

I use sulfamic acid on the warm or room temperature AR, followed by dry SMB with stirring. Only in cases with only small amounts of dissolved Au or high dilution do I get a delayed reaction. In these cases I evaporate the solution to half volume and add dry SMB again. I have never dissolved my SMB in water first so I can not speak on that subject.

Steve

 

[Yggdrasil]

Yes - evaporating it to dry (over the course of about 8 hours) then adding HCL and I end up with a thick mudlike goop.

Shark - I never thought about pre-heating the SMB (I usually use powder, I guess I can try disoolving it first, or try FeSO

That don't make much sense, do you have pictures from before?
If nothing else works, add enough HCl so all that can dissolves,
filter it well and cement out what ever precious metals are in there.

 

[Brett Novak]

OH Ding ding ding - I forgot to hit it with Sulfamic...(thanks for the reminder, need to stop and get more on the way home.)

I've got it back in the thick mud - will re-dilute it again with HCL and go from there.

thanks for jogging the ol' memory

 

[Shark]

I developed the habit of dissolving my smb the same as copperas just to keep a “similar” method for dropping gold the first time as the second. This way I use the same methods just different chemicals. And all that came about because I wanted to have different ways to accomplish the gold refine. I figured the more ways I knew, the better off I would be and the more I would learn.

 

[Proffshuggarn]

I use sulfamic acid on the warm or room temperature AR,

Pardon my newbie question, but I'm a little confused about Sulfamic Acid. Because after I started using it, it has become more difficult to drop anything at all, even though I am very careful with both the nitric (added drop by drop until nothing left to solve) and the Sulfamic acid (checking for reaction with only a little powder on top of a teaspoon), as well as I have a small "control-Au button" in the solution and in most cases it has been enough with just a little Sulfamic acid (only the teaspoon tip), or nothing at all.

I have learned that Sulfamic acid "does its thing" with possibly excess nitric acid, only at a temperature of 80-90'C? Or have I misunderstood?
Therefore, I have usually heated the solution to just under boiling because I have thought that the solution must be very hot for the Sulfamic acid to work? But when I read “warm or room temperature” solution, the confusion is total.
What about the temperature of the solution when using sulfamic acid? Thank you for taking the time to read. /Dennis

 

[Yggdrasil]

Pardon my newbie question, but I'm a little confused about Sulfamic Acid. Because after I started using it, it has become more difficult to drop anything at all, even though I am very careful with both the nitric (added drop by drop until nothing left to solve) and the Sulfamic acid (checking for reaction with only a little powder on top of a teaspoon), as well as I have a small "control-Au button" in the solution and in most cases it has been enough with just a little Sulfamic acid (only the teaspoon tip), or nothing at all.

I have learned that Sulfamic acid "does its thing" with possibly excess nitric acid, only at a temperature of 80-90'C? Or have I misunderstood?
Therefore, I have usually heated the solution to just under boiling because I have thought that the solution must be very hot for the Sulfamic acid to work? But when I read “warm or room temperature” solution, the confusion is total.
What about the temperature of the solution when using sulfamic acid? Thank you for taking the time to read. /Dennis

If there is not an excess of Nitric it will not react much.
Better go to SMB directly after Sulfuric and filtering.

 

[Martijn]

If there is not an excess of Nitric it will not react much.
Better go to SMB directly after Sulfuric Sulfamic and filtering.

Edited: strikethrough changed. sulfuric was correct. My apologies.

 

[Martijn]

Pardon my newbie question, but I'm a little confused about Sulfamic Acid. Because after I started using it, it has become more difficult to drop anything at all, even though I am very careful with both the nitric (added drop by drop until nothing left to solve) and the Sulfamic acid (checking for reaction with only a little powder on top of a teaspoon), as well as I have a small "control-Au button" in the solution and in most cases it has been enough with just a little Sulfamic acid (only the teaspoon tip), or nothing at all.

I have learned that Sulfamic acid "does its thing" with possibly excess nitric acid, only at a temperature of 80-90'C? Or have I misunderstood?
Therefore, I have usually heated the solution to just under boiling because I have thought that the solution must be very hot for the Sulfamic acid to work? But when I read “warm or room temperature” solution, the confusion is total.
What about the temperature of the solution when using sulfamic acid? Thank you for taking the time to read. /Dennis

If you used the adding 'drop by drop and let it react out in between eacht step' nitric method, no need for use of sulfamic acid.
Like shark said, predissolve your smb and I always add it cold right after filtering, don't bother evaporating it down to a syrup and never to dryness.
I let it sit on heat after all gold is dissolved, never boiling pregnant AR!, and take the watch glass off to let all the nitric leftovers escape.

Any minor trace of HNO3 will be 'consumed' by freshly precipitated gold as it is suspended throughout the solution.
If you have a solution left after unnessecary evaproration: there will be 20% HCl left, so the "pH or a lack of HCl" problem to make the SMB react; also never a problem.

In my humble hobbyist opinion of course. Correct me if i'm wrong.

Martijn.

 

[Yggdrasil]

Martin.
I meant Sulfuric, so you actually changed the meaning.
I should have added "to drop Lead"
But found it to be in common understanding.

 

[lazersteve]

For me heating with sulfamic hasn't been necessary nor has evaporation. I used dry SMB and sulfamic that is slightly moist from atmospheric water absorption. Evaporation may be required for you if you have only small amounts of Au in a proportionally excess volume of solution. Precipitations work better with highly concentrated solutions.

I use exclusively nitrate salts in my reactions. No need for nitric acid proper.

Steve

 

[lazersteve]

I want to add to my above posts. Water is definitely a requirement in my opinion for the SMB and sulfamic to work properly. When refining I add my water at the digestion stage of the reaction and work with covered beakers and buckets typically at ambient temperatures or only slightly above (~40C). I've posted the chemical reactions for SMB with gold chloride in the past. A quick search is in order if you are interested.

Steve

 

[Yggdrasil]

I want to add to my above posts. Water is definitely a requirement in my opinion for the SMB and sulfamic to work properly. When refining I add my water at the digestion stage of the reaction and work with covered beakers and buckets typically at ambient temperatures or only slightly above (~40C). I've posted the chemical reactions for SMB with gold chloride in the past. A quick search is in order if you are interested.

Steve

I do agree, but in this case I do not think it will solve the issue with Silver Chloride passifying the Gold.

Edited as I mixed up the threads.

 

[lazersteve]

This thread is about Au that won't precipitate I thought. I missed the part about AgCl passivation.

Steve

 

[Shark]

I do agree, but in this case I do not think it will solve the issue with Silver Chloride passifying the Gold.

I think that is another thread.

 

[Yggdrasil]

Sorry guys, I mixed up the threads