Mysterious Yellow Solution after Gold Pecipitate

[gertz115]

I followed Lazersteve's DVD video to process 350 grams of old karat gold (inquarted), at the point where I add SMB to drop gold from the yellow solution, after adding the calculated amount needed, solution was still yellow, so I added more SMB, to the point that I think I added an excess of SMB. No more gold is dropping but solution is still yellow gold. Stannous test is a false positve (purple blackish stain on a Qtip dissappears after a couple of hours) Gold that has actually dropped is way below what I expected. Can anyone pls tell me if this yellow solution has still Gold in it? and if yes, how do I recover it?

 

[glondor]

Tell us more. Did you denoxx ?

 

[Harold_V]

I dare say you still have free nitric in your solution. If you were to try washing the gold (using HCl) that has already been recovered, I expect you'll dissolve some of the gold in the process. I can think of no other reason for a test to dissolve after the fact, aside from an excess of nitric being present.

It is not easy evaporating nitric, and if you followed the (stupid) advice to evaporate three times and expect that the nitric will magically be gone, you are going to be sadly disappointed far more often than you will be satisfied with the process. The very best advice is to learn to use only the amount of acid required, but that requires patience, as you must give each addition of acid time to do its work.

If that idea isn't to your liking, you do have one other avenue to pursue. Evaporating (properly) is an art, one that is not readily mastered. It is for that reason I have long recommended that a piece of pure gold be used when evaporating, so unused nitric can (and will) be consumed instead. I highly recommend you consider that idea.

Harold

 

[gertz115]

Thanks for your replies guys. Yes, Harold, I have a strong feeling that whatever Gold is in my beaker will dissolve with a HCL wash. After reading Harold's response, the culprit may be excess free nitric. Since 70% Nitric Acid is unavailable here in Guam, I made my own Nitric Acid using Lazersteve's method of dissolving sodium nitrate prills in distilled water then adding concentrated sulfuric acid (liquid fire), this method claims a yield of 50% nitric acid. I used this homemade nitric acid in my dissolution process, but since it was only 50%, I had to repeat the dissolution stage 6 times to dissolve silver and copper in the inquarted gold, until I was able to get the remaining material to a brittle honeycomb like structure. I guess I overdid the dissolution phase. Is this how I got the excess nitric? If yes, what will be my best bet to get rid of excess and still recover that gold in the yellow solution? Thanks!

 

[philddreamer]

If you don't have a pure button of gold so you can follow Harold's method, and you don't have the patience to evaporate, ( you might end up applying too much heat and evaporate some of your gold), you can use some urea to neutralize the nitric. Don't make a habbit of using urea; learn how to calculate how much nitric will be required to digest the material, and add the nitric in small increments, as recommended above. This way, there will be no need to evaporate, or to add a button, nor any use of urea.

Take care & be safe!
Phil

 

[gertz115]

Thanks for all the help guys. Lazersteve actually replied to me thru email, here is it:

"Sounds like you need to add some water to the solution. Yellow colored solution is not always indicative of dissolved gold.
Purple swab is positive; brown with rotten egg smell is a typical false positive observation.
Dissappearing color on swab is indicative of excess nitric used. This could be why you are using too much SMB. Remove excess nitric by evaporating to a syrup, add HCl, then precipitate. Alternately, add sulfamic acid dissolved in warm water. Be careful as this addition can triple the solution volume quickly with foaming. Use enough sulfamic that the solution no longer foams when added.
Final gold weight depends on under karat (-1/2 karat normal), gemstone weight, and other processing losses."

I have a few questions:
Do I add water then evaporate? If yes, how much water do I need to add?
or can I just go straight to evaporation?

 

[philddreamer]

Go straight to evaporation.
Do you know how to properly evaporate a solution? You MUST NOT boil the solution, just heat until you see vapours coming off the top. If you boil you will loose some values. Do not cover the solution.
I would also recommend you do a search on the subject of "Evaporation" so you don't run into trouble.

Take care & be safe!
Phil

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=1055&p=9901&hilit=evaporating+nitric#p9901

 

[gertz115]

Thanks Phil. I am now starting the evaporation process. Photo below is my evaporation setup. Since I dont have a beaker large enough to fit 2000ml of the still yellow AR + SMB mix (with suspected excess nitric), I'm using a 2000ml flask. I am keeping an eye that it doesnt boil but does have consistent little bubbling over low heat. This is just half of the yellow solution, I will add more of the solution as the liquid decreases in volume. Please, if you have any more comments and suggestions, please post. Help me rescue this Gold! Thanks a lot. I will keep on posting as I go along.

 

[butcher]

Just a comment, adding more of the dilute solution (containing nitric and water) will dilute the nitric in your solution, just keep this in mind, they old chemist used steam tables or steam baths to evaporate the nitric with, as Hoke describes, these I believe kept the temperature about right for removing the nitric acid (without boiling the solution) around about 85 degrees C.

I would also put that flask in a corning casserole dish, or something similar it would catch any boil over and also help to protect the flask from breaking spreading heat from your heat source more evenly on bottom of the flask.

 

[BAMGOLD]

Wouldn't you want a container with the larger surface area to evaporate? as in just put the liquid in the casserole dish with a safety container under it (larger casserole dish) It would take along time to evaporate out of a Erlenmeyer flask.

 

[gertz115]

Thanks for your comment Butcher. I did not allow the solution to boil but a very gentle bubbling by low heat. After I have added the remaining solution that went all the way to 1800ml, the attached photo is 10 hours into the slow evaporation. I have noticed salt like crystals forming on the bottom. The solution is now more intensely yellow but I still have not noticed a syrupy solution that I am hoping to achieve. Maybe, it will take a few more hours and patience. According to Lazersteve's directions, I have to add water after I get the syrupy consistency, how much water should I add? And what is next after the addition of water?

 

[gertz115]

15 Hours Evaporation. Followed BamGold's suggestion of using a casserole to speed up evaporation. Solution is now syrupy but has a lot of salt-like crystals. Highly soluble in water. Can anyone tell me what this crystals are? Also a sidenote, I tested 10ml of the solution in a test tube added SMB dissolved in distilled water, no reaction, no precipitate. However, when I added the tested solution back to the casserole, the area where I poured in my just tested solution momentarily turns black for around 30 seconds and dissapears into yellow again. My stannous test has both positive (permanent purple-black stain) and false positive results (temporary dark brown stain).

 

[gertz115]

Added 800ml distilled water. 2nd evaporation. Note crystals have dissolved in water. Dou you think there is still recoverable gold in this solution? I can see a greenish tint in this solution.

 

[Harold_V]

You are wasting your time. To add water defeats the purpose of evaporation. Only when you have highly concentrated the solution will you expel any nitric, and then only if you add HCl, NOT WATER. Please refer to Hoke for a better understanding, as you clearly do not understand what you're trying to do. Also, ignore the admonition to repeat this process three times, as the number of times makes no difference if you aren't doing it correctly. You may achieve success with one iteration, or possibly not with six. I try to discourage all readers from doing these operations by count, as count is NOT reliable. Results will provide the required indicators of success, or the lack thereof.

The fact that a drop that was previously tested with stannous chloride was introduced to the main batch and yielded a reaction, which subsequently dissolved, is all the proof you need to understand that you have free nitric present.

Do NOT return drops of solution that have been tested. They should be sent to your stock pot, where they will be cemented by base metal and collected for future recovery. You should try to avoid adding tin to your solution at almost any cost, as it complicates filtration terribly.

You may have to drive your solution to the point of becoming almost dry before you'll succeed in removing the nitric. That's because you have it contaminated with substances you introduced previously. You may be best served by cementing the values with copper, then processing the small amount of powder that will be recovered. It will most likely be black in color, and not resemble gold in the least.

I say you have only a small amount present due to the color. It is too light in color and depth of color to suggest there's much gold present.

Evaporation. It makes no sense to attempt evaporation with a small surface area. The larger the area, the more tolerant will the solution be of heating, as the larger area dissipates heat at a greater rate, cutting the time it takes to evaporate, and making it much harder to make the solution boil. At no time should you see a boiling action, as that offers the risk of losing values.

Harold

 

[gertz115]

Well, for me it's Hoke's and Harold's word against Lazersteve...(from whom I purchased the Gold Refining Instructional DVD). Hoke and Harold says "Evaporate then HCl", Lazersteve's advice is "Evaporate to syrupy then add water". But anyway, an update on the solution after the 2nd evaporation process, it turned light green! Stannous test is now a negative. I have stopped evaporation and decanted the now green solution to my AR stock container, (see photo). I am now looking at the remaining "black metal and gray dirt" leftover that did not dissolve during the AR stage, using Lazersteve's Modified Poormans Aqua Regia. I have a hunch that the remaining Gold is still embedded on the solid metal pieces. I'll go back to the Nitric dissolution process then repeat AR again. Thanks for all the help guys.

 

[kurt]

As Harold suggested you may be best served at this point to cement with copper any remaining values in the solution that did not drop all your gold when you originaly tried to drop with SMB - doing this is going to give you a dirty "recovery" as you will get copper chloride with gold cement.

Another option I would consider would be to take the gold powder you have already droped - put it through the recomended washes for Karat gold (water/HCL/water/ammoina/water) melt a button - put the button in the free nitric solution - add low heat (same as evaporation) until there is no more reaction on the botton.

Because you already have SMB in the solution it will most likely precip gold as gold goes into solution (from the button) I don't know for sure if this will work - but it is what I would try first to avoid copper chloride contamination by cementing with copper.

I would also think you will want the solution rather dilute when you ad the button/heat to (1) allow for evaporation while reacting the button & (2) so the solution is dilute to allow SMB to precip gold as gold goes into solution.

Just an idea (open to comment)

Kurt

 

[kurt]

Some where along the line I read where you got a crystal formation when evaporating - That could be where your gold is ???

You need to "slow down" & "wait" for members to comment - then ask questions to make sure you are understanding what you are being told - before you proceed

Other wise all you are doing is complicating the situation - for both you & the problem you are trying to solve & the members that are trying to help you.

As a side note - I think you ether miss under stood Steve's instruction or didn't catch all of it (as a result of your being in a hurry) I don't have the DVD but I am willing to bet that Steve's instruction to dilute after evaporation - is to do so - ONLY - after you are sure you have got rid of free nitric.

The evaporation HCL addition process to rid free nitric is "very tricky" & if you don't do it right you are beating your head against the wall.

Kurt

 

[kurt]

Here is something I posted in another thread about the evaporation process - hope it helps you understand it better -----

I am betting you have free nitric yet. The evaporation HCL addition method of getting rid of free nitric is a bit tricky. If you don't evaporate down far enough before adding the HCL the added HCL will not expel the free nitric & there is a fine line between evaporating far enough for the HCL to do it's job & evaporating to far to where your AuCl starts forming a crust.

You can tell if you evaporated far enough or not. When you ad the HCL you should get a strong fizz & a puff of brown smoke. If you only get a week sputter & white smoke you did not evaporate far enough. One is the chemical reaction of the nitric being expelled - the other is just the cold HCL hitting the hot AR.

If you don't evaporate far enough to get the chemical reaction to expell the nitric - it doesn't mater how many times you do it - you will still have free nitric. --- That is why it is important to calculate the amount of nitric just needed to dissolve your gold (so you don't get a lot of free nitric) & then go with Harolds method of adding a gold button with some heat to use up any possible free nitric. Then you don't need to evaporate.

Kurt

 

[butcher]

I do not see the difference in Laser Steve’s advice and Harold’s, as they would both have worked if the situation was as you described (at that particular time when the questions were asked and with what details of the situation were given), several details I did not see in your description of the problem and more information added later after you tried Laser Steve’s solution to your problem as you described it to him, later you showed a picture and more details of the situation were revealed at this point Harold noticed from your picture and the formation of salts, color of solution, that this was just not your normal gold chloride solution loaded with gold, the color of the solution, it also looked very strange to me, I thought it looked more like HCl/Cl with salt in solution some copper and not much gold to me, nothing like concentrated evaporated aqua regia with 350 grams of gold in solution, it looked dilute but was forming salts, this was not normal for gold chloride solution made from aqua regia at this stage in refining, Harold is very sharp and noticed a problem, and gave great advice, as to what you had was not what the original description of where you were in the process described (at the point Laser Steve answered your questions), Both Laser Steve's and Harold's advice can be taken to the bank, but you also have to understand that they are not the one who has worked on your process, seeing or doing all of the reactions up until you had a problem, they are only answering on the details or clue's you give them, and have only a few clues as to what you have done so far and without being the one doing the process from beginning to ending they are only going by the few clues that you gave them as to what you have done so far and how, It is very hard to give advice when you do not know all of the little details, that can make a big difference as to what you actually have. I also did not notice any mention of using the poor-mans aqua regia and not pure acids until after everyone gave you advice, I suspect there are many details of where a problem could have been made in the process, that you have not revealed.

 

[gertz115]

Thanks a lot Kurt and Butcher. I retested the solution using stannous and get a false positive with a rotten egg smell. It is dark brown and eventually fades after 2-3 hours. (see 1st photo of Upper QTip - Actual Positive tested before adding SMB. Lower QTip - False Positive after 2nd evaporation)


Lazersteve's DVD has actually helped me succeed in my first process where I followed all his instructions to the letter, I got a beautiful 27 gram gold ingot. However, I decided to produce my own nitric for my 2nd batch of scrap karat jewelry. (We dont have a local supply for 70% Nitric Acid, for my first batch, I ordered 1 liter and had it shipped by boat from California, I had to pay over $100 for hazaradous materials fee to the shipping company)
This homemade nitric is what I used to dissolve base metals after inquartation. Estimated strength of this homemade nitric is 50%, so instead of mixing the usual 70% nitric to an equal amount of H2O. I just used the homemade nitric straight up without any dilution in water for dissolution. I noticed that this acid was weak, so I did the dissolution process 5 times. During the 5th time of dissolution, there was not as much red-brown fumes as the first four, but the inquarted gold was still mostly solid with only a few brittle pieces. I proceeded to Aqua Regia anyway...thats where I failed. Because after AR (that resulted in the mysterious yellow solution topic of this thread), I still have these undissolved material which clearly looks like gold:


This is where the remainder of the gold is! Not in the mysterious yellow solution that I thought it was in. Now here's my question to the experts: I know I need to run these bits and pieces of leftover gold through AR again, I dont like the idea of putting it back in AR again for there was no/very little reaction with these bits and pieces to AR. (using Lazersteve's Modified Poormans Aqua Regia), I was thinking of melting these pieces, without inquarting, and pouring it into cornflakes again before putting it on AR. Is this the right thing to do???

Thanks everyone of your comments and suggestions, you've all been helpful. More power to the forum!