# Fixing up my poormans AR screw-up



## bswartzwelder (Jul 28, 2013)

Some time ago, I had such good luck with the AP method, I decided to try my hand at refining some gold nuggets with poormans AR. I weighed out the nuggets and came up with a little over 1 Troy ounce. I know what I'm doing (tongue in cheek), so I went to my handy dandy chart and measured out the HCl and NaNO3 I would be needing and put them in a beaker on my stirring plate with no additional heat added. As the chemicals were stirring, I added the gold nuggets. After quite a while, not all the nuggets had completely dissolved, so I added an unmeasured amount of more NaNO3 and a little more HCl. Evidently, it appeared my original measurements were off somewhere. Still, not all the gold dissolved. It left tiny chunks which seemed to have turned black on the bottom of the beaker. Next, I ran everything through a filter and saved the little chunks which look to be like small grains of sand. I'll try to reprocess them later after much more reading. Now, I have a beaker with probably close to an ounce of gold dissolved in poormans AR. I know of several ways to attack this problem: 1. EVAPORATE (NOT BOIL) the solution until it becomes thick and syrupy and then reconstitute with more HCl. Do this 3 times, then add a little Sulfamic acid to ensure I have gotten rid of all the Nitric acid. 2. Mix Sulfamic acid with water and add it to the solution to neutralize the Nitric acid. This method may take up to triple the volume of the solution I now have to get rid of all the nitric acid. or 3. Drop in more gold and just let the Nitric do what it was originally supposed to do. Lately, I have been giving option 3 some thought and like it. I have a 1 ounce (not troy) gold nugget (manmade) which I won in a contest several years ago. I took it to a jeweler and he did the stone test and said it was 22 karat. I plan to dissolve it anyway, so why not use it to kill off excess Nitric? Now for the problem. No matter what way I go, I don't remember reading any definitive test to prove that all Nitric has been used up. I don't just want to mix up a liter of Sulfamic acid either. The 1 ounce nugget has a lot of surface area which will be exposed if I drop it into the present solution. It is my thought that I should probably add more HCl to the mix to make sure there is enough HCl to react with all the NaNO3 produced AR. Is there any way to predict the amount of HCl I will need? Will adding an overabundance of HCl cause any undesired problems other than the waste which will be produced and will need disposal? With the batch of circuit boards I processed in AP, I then processed them in HCl/Chlorox and dropped with SMB. I tested that solution with stannous chloride before dropping with SMB and got a good, dark, positive result. Then after I dropped the gold, I retested the solution and the swab didn't change color at all. To me, this showed I had all the gold out of the solution. I left it sit for several days and carefully decanted as much of the clear solution (through a filter) as I could without pouring off any gold. Then, I added HCl and boiled it, let it sit, decanted most of the clear liquid (again through a filter), then boiled in distilled water. I am saving that gold for further cleaning with HCl and distilled water before I opt to pour an ingot.


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## solar_plasma (Jul 28, 2013)

a) forum handbook 2:


> Four parts HCl to 1 Part HNO3,; If I remember correctly, Hoke states 4 fluid ounces of HCl + 1 fluid ounce HNO3 to 1 troy ounce gold scrap.


 so you only have to guess or calculate, how much HCl might be necessary at maximum. (there are also infos about it in Hoke and some calculations in the forum, forum handbook has just been quickest to search)

b) excess HCl doesn't harm the reaction or the precipitation, as you know from your experiences with ACl

Hope I could help

Björn


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## artart47 (Jul 28, 2013)

Hi!
A test to see if there is too much nitric ( free nitric) If you were to do a test for gold with stannis chloride and have free nitric, gold would come out of solution and form the purple color that is a positive result. But, if there is free nitric in the solution it will immediatly redissolve the gold and the test would show a false negative. If you test your SnCl on a known gold solution to make sure it works, then test your solution and get a negative and you know there is gold in it, then you can assume there is free nitric,
Hope it helps 
artart47


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## solar_plasma (Jul 28, 2013)

Something I do, when I am not sure, is to take a small probe and add smb to see, if the precipitation works good. For my taste this is the easiest way. Or I lay a glucose strip with its very thin plating of very pure gold in it and watch if the gold is gone after an hour. If so, then there is still NOCl and/or Cl(nasc.).

Other common methods like in Hoke, worked not as good in my settings, maybe because I have often only some 1/10 g of gold in 100-300 ml solution (often the weaker 25% Cl), so I worked with HNO3 amounts of only some 1/10ml - 3 ml.


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## bswartzwelder (Jul 28, 2013)

I purchased a small bottle of gold chloride with a known gold content. Before I ever use stannous on an unknown, I ALWAYS test the stannous first to make sure it is still good. It's cheap insurance. I KNOW my solution has gold in it, in fact, a lot of gold. I just want to make sure the nitric is gone so I don't re-dissolve any gold when I precipitate. I appreciate all the help and have learned my lesson about adding too much nitric. Same goes with adding bleach to an HCl/Chlorox mixture. If I add more HCl (which will do no harm) and then add my large gold nugget and let it sit for a day or two, I assume ALL the nitric will be used up trying to dissolve the larger nugget.


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## Geo (Jul 28, 2013)

add a small amount of solution of SMB and water. some gold will precipitate. slowly heat the solution until the precipitated gold re-dissolves. depending on the reaction, you may have to repeat. i would start with a gram and go from there.

be careful to use a catch pan. finely divided gold will dissolve quickly and may boil over.


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## niteliteone (Jul 29, 2013)

bswartzwelder said:


> Some time ago, I had such good luck with the AP method, I decided to try my hand at refining some gold nuggets with poormans AR. I weighed out the nuggets and came up with a little over 1 Troy ounce. I know what I'm doing (tongue in cheek),
> (big snip)


Did you by chance remove the majority of base metals and "ides *"Before"* trying to dissolve the gold ???
remember garbage in = garbage out


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## bswartzwelder (Jul 29, 2013)

I added about 300 ml of HCl to the original solution and hung my gold nugget in the solution. It was suspended in the beaker by a piece of nylon fishing line wrapped around a glass stirring rod. I have the stirrer on at a rather slow speed to minimize any splashing. I have added a picture of the nugget which I took with a 7.2 mega pixel camera. I don't know why the picture isn't of better quality. I'm going to let the nugget in the beaker for several hours then reweigh it to see how much of it actually dissolved. This should get rid of any excess nitric in the solution and allow me to precipitate the gold this weekend when my son comes in for a visit.


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## bswartzwelder (Jul 29, 2013)

After 6 hours in the beaker with the stirrer turned on, the man made nugget dropped 1.64 grams from 27.47 grams down to 25.83 grams. I hope this has killed off any nitric which may have been left in the solution.


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## Geo (Jul 29, 2013)

did you heat? if you heat the solution, it will dissolve more. if you didnt heat, it only used the free nitric that could be used at room temperature.


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## bswartzwelder (Aug 5, 2013)

My youngest son Karl) came by for a visit late Saturday afternoon, and after a quick meal, we had a lot to catch up on. I wanted to show him gold precipitating so, I brought out my stirring plate stannous solution, gold chloride solution, and SMB (plus all the little things we might need). It had started to rain, so instead of doing this in the driveway, we set up on the front porch. 

This is the solution which had WAY TOO MUCH Sodium Nitrate (NaNO3) added to it. Long before his arrival, I added between 200 and 300 ml of HCl and dropped in a 1 (NOT TROY) ounce man made gold nugget. It was all bright and shiny and a local jeweler tested it and said it was 22k. After 6 hours in the solution, I took the nugget out and weighted it again. It had lost 1.64 grams and had taken on an appearance like it had been sand blasted with very fine sand. The color was beautiful. I assumed (incorrectly) that the gold had used up all the nitric. In front of my son that evening, with poor lighting, I tested my stannous solution by adding a drop to the end of a Q-tip which I had dipped into the gold chloride solution. Immediately, it turned a deep black. The stannous was still good and working like a charm. Next, I dipped a Q-tip into my beaker and it instantly turned black when a drop of stannous was dropped onto it. My son now realized there was gold in the beaker. I then added a small plastic spoonful of SMB to the beaker which was on stir. The solution turned milky white from the color of the SMB. Soon, it turned brownish. I retested and there was still gold in the solution. Added another spoonful of SMB. Ended up doing this 3 or 4 more times. After the stir function was turned off, a nice thick coating of brown powdered gold appeared which quickly settled to the bottom of the beaker. The liquid changed from the rich golden orange to a weakly colored solution. I had my gold, or so I thought. Karl left later on that evening and I decided to work with the gold next morning. I never got anything except a positive response for gold in solution in that beaker.

Next morning, with good lighting, I saw the gold along with some white un-dissolved SMB in the bottom of the beaker. The solution had returned to is rich golden yellow color indicating there was still nitric in solution re-dissolving the gold. I slowly poured as much liquid as I could through a filter without disturbing the gold and white SMB in the original beaker (beaker 1). I washed my filter paper into beaker 1 with the gold powder in the bottom (there is a lot of gold in there), added a little water for good measure (into beaker 1), and turned on the stirrer and heat. Soon, the white powder had dissolved, but the solution still tested positive for dissolved gold in it. I set beaker 1 aside. I then turned my attention to the beaker (beaker 2) with the majority of the gold solution, (but little or no powdered gold in it) on stir and slowly added a spoonful of SMB. Since the liquid had returned to its original rich golden color, I expected it to have some nitric in it, but was shocked to see brown fumes coming off gassing from the beaker. I had been fairly certain that all the HCl I had added and the additional gold had gotten rid of the nitric. I also added a spoonful of sulfamic acid crystals to the solution. It dissolved completely. I thought the sulfamic acid would neutralize the excess nitric and the SMB would cause the gold to drop. No more gold seems to have dropped at this point, and I don't want to just inundate the solution with more SMB unless necessary. That's where I am right now.

My plan of attack at this point is to carefully decant the gold in the bottom of beaker 1 into another beaker (beaker 3) which has gold powder precipitated from a previous recovery from circuit board foils. Then I will put beaker 1 or beaker 2 on the stirring hot plate with both the stir and heat functions turned on. I will heat to just below a boil to evaporate the excess nitric, and since the solutions will have far less volume at that point, combine them so I only have 1 beaker to deal with. I will evaporate down to a thick syrupy mixture, add HCl to bring it back to almost its original volume, then repeat 2 more times. Then add HCl one last time and try to precipitate again. Does anyone see a flaw in my plan of attack? I know I've made several other mistakes, but just want to recover what gold is left in the beakers. Also, next time I try to precipitate, (I am not trying to refine at this point, just recover the gold) should I continue to use SMB? I have plenty of it, but also have Copperas and Oxalic acid as well. Would changing precipitant be a good idea or a bad idea? All I will do until I hear from you guys is evaporate the solutions down.

By the way, when Karl saw that gold coming out of solution, the looks on his face and my wifes' face (she had never watched any of this previously) were priceless. I didn't admit to them that I had screwed up the process. Why denigrate myself from being a gold god in their eyes? I knew there were mistakes made, and I was unimpressed by my mistakes. Next time I try to recover gold, I will be more accurate in calculating the amount of nitric needed and once I reach midpoint in nitric addition, nitric will be added by the drop or very small amounts of NaNO3 until all the gold dissolves. Years age when first introducing me to her friends, my wife would laughingly say that I'm not too smart, but at least I'm trainable.


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## butcher (Aug 5, 2013)

Your plan sounds pretty good to me, the gold may precipitate after being concentrated and excess HNO3 removed, you may have to add another dose of SMB, to get more SO2 gas in solution to precipitate the gold from your diluted solution. if the plan does not work you can cement the gold from the acidic solution using the copper buss bar.

You did do good, and showed your wife and son you can get the gold, and you showed them you could even get it from a very difficult situation, getting your gold from difficult situations was showing them that you can get that gold, you will also be able to show them later when you melt that gold.

You are learning from your mistakes, which will help you become better at getting your gold, and will also help you make less mistakes in doing it.


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## bswartzwelder (Aug 5, 2013)

Thanks for the kind words, Butcher. I put beaker 2 with 900 ml of solution on my stirring hot plate and watched it constantly to make sure it didn't boil. I saw steam rising very quickly and set a 20 inch fan upwind of it to blow away any vapors. After 2.5 hours, the volume went from 900 ml to 800 ml which is a LLLOOONNNGGG way from the syrupy solution it needs to be. In actual fact, after 2.5 hours I could grab the beaker and move it with my bare hands from the hot plate. I need to rethink my stirring hot plate and use another hot plate which doesn't stir, but can attain much higher temperatures. Also, a beaker with more surface area on the bottom might help, but I'll have to order that. Since my first screw up with the Shor system several years ago, I've been very patient when it comes to working with gold recovery and chemicals, but dang, this is a slow process.


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## g_axelsson (Aug 5, 2013)

I got a crystallisation dish from a friend, it is much better than a beaker. The low and wide design gives a higher rate of evaporation. You need good air flow to rapid evaporate a liquid.

https://www.google.se/search?q=crystallisation+dish

You could also add a fan to speed up the evaporation.

Göran


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## bswartzwelder (Aug 6, 2013)

Goran,
Thank you for the information about the dish. I did set up a 20 inch fan as stated in my previous post. No matter which course of action I take, I have to either increase the surface area for the evaporation or increase the heat. I do have a hotplate which gets much hotter than the cheap lab unit I purchased on eBay. Hopefully, in the future, I'll be wise enough not to make the same stupid mistakes. Originally, I weighed out my gold and thought for X amount of gold, I'll need Y amounts of HCl and Z amounts of NaNO3. So, I carefully added the gold and chemicals and put it on stir. When not quite all the gold dissolved, I splashed in some more HCl and a spoonful of NaNO3. That's where the problems started.

I left it sit for several months while I researched my next plan of attack. I added a 1 ounce man made 22k gold nugget to the solution and after 6 hours, it weighed 1.64 grams less than when it started. I figured the HNO3 problem had been resolved. I then added a small amount of sulfamic acid to be sure the HNO3 was gone. Then, in front of my son and wife, I started adding spoonfuls of SMB. Quite a bit of gold dropped that evening and the solution turned from a rich orange/golden yellow to a weak slightly yellow liquid. But, once I turned off the stirrer, a nice thick layer of brown powder settled quickly to the bottom. Next morning, the solution had once again taken on the rich golden color and there was some SMB powder left on the bottom. At that time, I knew that I hadn't gotten rid of the excess nitric and it had stolen some of the gold which had precipitated the night before and dissolved it back into my solution. I hate that thief and am determined to overcome what it has done and hopefully not see it again.

I poured off as much of the liquid as possible without disturbing the sediment, then added H2O to the sediment to see if the SMB would dissolve (and it did). Then I once again poured off the excess liquid into the first beaker and washed the gold into the beaker where I have been saving my recovered powdered gold.

Yesterday, in the process of evaporating the original solution, the volume dropped from 900 ml to about 700 ml. A lot of white crystals/powder have formed either on top of the solution or have dropped to the bottom. So much so, that the stir bar will no longer stay in position and stir the contents. That has to be excess NaNO3, excess SMB, excess sulfamic acid, or some combination of all three. Originally, I thought of pouring that solution through a metal mesh kitchen strainer, but decided I'd rather not introduce any more new metals into the solution at this time. I will filter the white stuff out of the solution, then restart the evaporation process with my other hot plate. Mother Nature has turned against me as it is raining now, and is supposed to rain for the rest of the week.

Again, while I have been reading Hoke and the forum for several years now, I haven't been totally comfortable with the prospect that what little precious gold I have can be lost. That fear has lessened, but I still worry about making mistakes like this one. I guess that's always going to be a possibility, so I can only hope to minimize my errors. A HUGE THANK YOU to you Goran, Butcher, and everyone else who has helped me through this process. While it's raining outside, I can work inside on my lathe making parts for my pyrolyzer/incinerator. Mother Nature hasn't won, she only slowed me down for the time being.


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## butcher (Aug 6, 2013)

I have a plastic cup strainer with a handle that has a plastic screen (some type of poly plastic that holds up well to acidic solutions) it was bought someplace where they sell kitchen supplies, it is a great tool to separate small chunks of metals from the finer powders and liquids, I have a fiber glass stir rod I use to stir the powder in the screen as the finer powder is washed through the screen (usually with the same solution that formed the salts, the liquid usually being transferred with the suction bulb tool, a small funnel under the screen so everything that passes the screen ends up in the jar below. 

This is sometimes very helpful to separate larger salt crystals or sometimes salts of differing metals, the finer metal salts or pieces that pass the screen can also be easier to wash or dissolve, or in the case of silver be converted easier it can also kind of pre-stir the powders, great for separating bugs and sometimes things I wish to incinerate, sometimes for hard to filter material I will shred some toilet paper stir it up into solution well and screen it, before filtering the liquid, the small plastic screen cup is a handy little tool.

I do use stainless steel screens but not where acids or salts are involved. I also use some plastic kitchen spaghetti strainers (plastic bowls with lots of small holes) these come in handy for separating liquids from pieces of material like chips.


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## bswartzwelder (Aug 7, 2013)

I purchased some large kitchen strainers (the type you mention) at Walmart. They are white with black handles and I think they only cost like a $1.97 each (I may be wrong on the price). BUT, the great thing is they sit over the opening of my 5 gallon buckets perfectly. A large (commercial size) coffee filter also fits in the strainer very nicely. It's amazing what you can find when you look a little. I have used them with great success when filtering all the little pieces of gold foil out of my 5 gallon AP buckets. I'm hoping to get out today and look for the small plastic strainer. I know if I use a filter paper it will catch all the powders, but if I wash the paper to get the values back, I'll be re dissolving some of the chemicals which I wanted to get rid of in the first place. Also, as the solution thickens, it will take forever to pass through the pores in the filter paper. That's the primary reason for the strainer. If the only thing I can find is the one with the stainless steel screen, I'll use it because the solution will pass through so quickly there will be little chance that much of it would dissolve. Turn it over and tap it on something and the powders/crystals should fall off, then a quick rinse with good old H2O. There is a light at the end of the tunnel. 

Karl's older brother Robert stopped by for a few minutes last night and I showed him my gold collection beaker. It's a 1000 ml beaker and has almost an eighth inch of fine brown powder in the bottom. He was impressed and I think he will want to join Karl when we put it in the furnace and pour it into the mold.


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## bswartzwelder (Aug 18, 2013)

On page 58 of Hoke, she states that when gold is slow to precipitate, "Usually the trouble is that the liquid contains too high a concentration of acid; that is, maybe he failed to evaporate off all his excess nitric acid; or maybe he used too much sulphuric or hydrochloric acid in previous steps. One remedy is to add water to dilute the liquid and reduce the concentration of acid; another is to add pinches of sodium carbonate, a very small quantity at a time, stirring well." 

If adding sodium carbonate works, why waste all the time required to evaporate a solution down to a thick syrupy consistency? I kept adding HCl to my original mess, and washed the beakers down with a spray of water till I ended up with over 1400 ml of solutions. Yesterday, after 4 or 5 days of evaporation, it finally evaporated down to a little over 200 ml and seems to be starting to get thick. I may still have some evaporating to go, but if sodium carbonate works, why spend the excessive amount of time to evaporate? 

I really like reading Hoke as it seems I see something new (or something I forgot) since the previous read. The prices she quote on lab apparatus makes me laugh, but I really would like to see the chemical formulations in parenthesis next to the chemical names to better understand what all is involved. Also, I know the technology wasn't available to her, but perhaps monitoring the Ph of a solution when adding "pinches" of sodium carbonate might be easier to follow. I will continue to evaporate and then add HCl in small increments until no brown fumes are given off, then evaporate again, but if I knew what Ph to look for, it might be a more accurate way to do things.


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## FrugalRefiner (Aug 18, 2013)

If you go back to page 57, you'll find she begins the section by saying:


C. M. Hoke said:


> As in Chapter V, you must remove the excess nitric acid by evaporating the solution to a syrup, adding hydrochloric acid, and _boiling_ (she means evaporating) down again, finally diluting with considerable water and getting rid of all sediment. This procedure is necessary when you use copperas, or sulphur dioxide, or any other precipitant.


I believe she is only suggesting the use of sodium carbonate to remove any remaining traces of excess nitric acid, not for removing any large quantity of excess. Notice that she said:


> add pinches of sodium carbonate, a very small quantity at a time


I see 2 problems in using sodium carbonate; 1) it is adding an unnecessary contaminant to your solution, and, 2) adding sodium carbonate will raise the pH of your solution and could cause the undesired precipitation of any base metals that are still in your solution.

If you need to remove remaining traces of nitric, sulfamic acid would probably be a better approach.

Dave


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## bswartzwelder (Aug 18, 2013)

Unfortunately, if I recall correctly (and at this point, I'm not so sure), it takes a lot of sulfamic acid to kill excess nitric, and it is better than the sodium carbonate as far as NOT adding contaminants. It was just another thought. I should have assumed if I didn't read it here first, not to question it. But, after all, IT WAS HOKE!


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## Harold_V (Aug 19, 2013)

The best trick is to use an added button of pure gold when evaporating. It will readily consume any free nitric, assuming you have some free HCl present. It also allows for solutions to be evaporated far less, although in my case, my objective was twofold---eliminate any unused nitric, but to also concentrate my solutions, which was my preferred method. 

In regards to issues with too much sulfuric or HCl----never in my more than 20 years of refining did I ever experience any issues with too much of either, and there were some solutions that had a huge overage of HCl. Sulfuric was never a problem, because it was used sparingly, simply to ensure no lead was carried through the process. 

Think about keeping a small button of gold on hand for evaporating. It's a decision you won't regret. 

Harold


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## bswartzwelder (Aug 19, 2013)

Thank you, Harold,

Long before I started evaporating the solution, I placed a 1 ounce man made gold nugget into the solution. It was scratch tested at a local jewelry store and I was told it was 22k. It was in the solution for a full 6 hours and 1.64 grams of it actually did dissolve. I should have realized that if I had left it in my heated solution, it might have helped get rid of excess nitric. Quite a bit of the excess NaNO3 and SMB that I used precipitated out of the solution, so I will soon be adding HCl and then re-evaporating as per Hoke (and almost everyone else on the forum).


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## Geo (Aug 19, 2013)

the sodium carbonate used as she described is the same as the way i described when using SMB. it precipitates a small amount of metal which in turn gets dissolved using up the free nitric.


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## bswartzwelder (Aug 26, 2013)

Yesterday, when my pyrolyzer hit a small snag, I got out the beaker of solution which I had evaporated down. A couple of days ago, I once again filtered out a whitish sediment from the bottom of the beaker, then added about 100 ml of HCl and set it aside. Yesterday, I put the beaker on my stirring hot plate and turned the heat on low and the stir to slow (about 300 rpm). Then I added a small plastic spoonful of SMB, a small amount at a time. After a minute or two, the white color of the SMB spinning around in the solution turned dark. I shut everything down and noticed the liquid started to settle rather rapidly. A couple of hours later, there was a nice brown sediment on the bottom. I plan to decant this off and restart the evaporation process for the second time. 

I dipped a Q-tip into the solution, and dropped a drop of stannous chloride test solution on it. The Q-tip turned very dark, almost black. This indicated to me that I hadn't yet removed all the nitric which was in my original solution. If there's gold in there, there had to be excess nitric to allow it to dissolve. 

When I made my test solution, I used HCl, a little H2O, and a couple of beads of pure tin shot. I then added a couple of crystals of stannous chloride anhydrous. It is probably a fairly strong solution, so I would expect it to test positive even when there isn't much gold in the solution.


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## g_axelsson (Aug 26, 2013)

The color of the stannous test comes from colloidal gold, that gives the purple - black color, not the stannous. It only turns the gold chloride into a gold colloid.
With the help of dilution you can use the color as a measurement of how much gold you have in a solution. You only need some reference solutions to compare with.

Depending on how much nitric acid was used in the beginning I would either denox the solution via evaporation or add a button of gold.

Have you added a couple of drops of sulfuric acid? You said you got a white sediment when evaporating, that could be lead chloride in your solution.

Göran


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## FrugalRefiner (Aug 26, 2013)

bswartzwelder said:


> Yesterday, when my pyrolyzer hit a small snag, I got out the beaker of solution which I had evaporated down. A couple of days ago, I once again filtered out a whitish sediment from the bottom of the beaker, then added about 100 ml of HCl and set it aside. Yesterday, I put the beaker on my stirring hot plate and turned the heat on low and the stir to slow (about 300 rpm). Then I added a small plastic spoonful of SMB, a small amount at a time. After a minute or two, the white color of the SMB spinning around in the solution turned dark. I shut everything down and noticed the liquid started to settle rather rapidly. A couple of hours later, there was a nice brown sediment on the bottom. I plan to decant this off and restart the evaporation process for the second time.
> 
> I dipped a Q-tip into the solution, and dropped a drop of stannous chloride test solution on it. The Q-tip turned very dark, almost black. This indicated to me that I hadn't yet removed all the nitric which was in my original solution. If there's gold in there, there had to be excess nitric to allow it to dissolve.
> 
> When I made my test solution, I used HCl, a little H2O, and a couple of beads of pure tin shot. I then added a couple of crystals of stannous chloride anhydrous. It is probably a fairly strong solution, so I would expect it to test positive even when there isn't much gold in the solution.


Bert,

I disagree with your conclusion when you say the stannous test "indicated to me that I hadn't yet removed all the nitric which was in my original solution." 

You said you added some SMB and got "a nice brown sediment on the bottom" If that sediment is still there, you don't have any nitric left (assuming there is a bit of HCl still in the solution) or the sediment would dissolve back into solution.

To me, the stannous test simply indicates that you still have gold in solution. That's good. It means you haven't added too much SMB, which could cause base metals to start to precipitate as well. Add some more SMB, stir well, then test again. As long as you're seeing more sediment, but still getting a positive stannous test, just keep adding small amounts of SMB until the stannous test is negative.

Be careful not to confuse a positive stannous test - deep purple to black, with a false positive - very dark brown, which you can see if you've added too much SMB.

Hope that makes sense and helps.

Dave


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## Pantherlikher (Aug 26, 2013)

Howdy Ya'll...
It sounds like too much SMB which can cause a false positive. 

I have been collecting gold from gold rimmed dishes and other nick nacks and glass...etc. I also have AP running and have sediment from that.

When the gold takes too long to dissolve from the plates, I let sit overnight untill things stop dissolving. I'll then precipitate with a 1/2 gram of SMB and let sit 3 days untill everything settles. I then use the little plastic strainer mentioned, find them at dollar stores and works great with the small 1 cup coffee filters. The filtered solution I put right in the AP sediment which dissolves alittle, precipates. What ever it wants. The sediment doesn't usually do much but once I have gotten positive for gold and added another 1/2 gram SMB and gotten more gold from it.

My point/question is: If you think you have nitric left over and can't seem to get rid of it, why not put your AP sediment in it and let it sit for a day or 2?

Wouldn't it dissolve untill nitric's gone? Added bonus would be first refinning of some of the AP sediment. Granted, if you feel the need to be perfectly exact with "what goes in, comes out measurements"...not me, get'er done... This would be a problem.

B.S.

...I'm not a technical perfectionalist but my O.C.D. and A.D.D. force me to find a solution to any and every bump in the road...

(Edited for spelling after reading it twice before submitting)


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## bswartzwelder (Aug 27, 2013)

OK. Here is my reasoning. In the beginning, I really dumped a lot of Sodium nitrate into my HCl because not all of the gold would dissolve. As a result, I ended up with a huge excess of Nitric, and still not all the gold dissolved. Since the gold was in the form of placer nuggets, I now assume that somehow they became oxidized causing them to turn black and preventing them from dissolving completely. Then, I tried my first precipitation. I DID get some brown powder settling to the bottom and my solution turned almost clear with the exception of the powdered gold which had yet to settle. I kept adding SMB hoping the solution would show that all the gold had precipitated. Did not happen. Next morning, there was still brown powder in the bottom of the beaker, but the solution had turned to its familiar yellow color. At no time, when I tested the solution did I ever get a negative for gold. It was ALWAYS positive, which I took to mean not all the gold had precipitated. 

Let me say here that I purchased Gold Chloride solution online from a chemical supplier and use it as my "standard" for testing my Stannous Chloride solution. Would really cause a lot of problems if my stannous gave me a false negative when in fact, there was gold in my solution. I dip a Q-tip into my standard gold chloride solution and then drop a single drop of my stannous chloride solution on it. So far, my stannous chloride has always turned the end of the Q-tip a rich black color.

Now, I knew I had added way too much NaNO3 and way too much SMB. I felt certain I needed to get rid of excess Nitric, so I hung another gold nugget (1 ounce of 22k) into my solution. Only 1.64 grams of gold dissolved from it. I added a very small amount of SMB and nothing happened. Still thinking the problem was excess Nitric, I started to evaporate it as per almost everyone including Ms. Hoke. I evaporated for several days. next morning (for each of several days) there was a white sediment. At first it looked like crystals, and then it started to look more like a powder. Then, according to Hoke, I added more HCl to reconstitute the solution. I figured it wouldn't hurt anything at this point to try to precipitate any gold that I could, so I carefully added one small spoonful of SMB. The white SMB looked like a snow storm swirling around in the yellow solution. Then, the snow storm turned brown, so I shut off the stir and heat functions and let it rest overnight.

I carefully decanted the solution from the sediment. The sediment went into a beaker with the sediment I got from dissolving foils using HCl/Chlorox. The solution, still yellow has only been evaporated 1 time. As per members on the forum (and Ms. Hoke), I plan on repeating the evaporation process up to a total of three times, or until the solution shows no gold is dissolved in it. If there is still gold in the solution, there must have been nitric there to cause it to dissolve. As some gold precipitates, there has to be less in the solution. Once all the nitric is gone, the gold cannot re-dissolve. Before I start evaporation for the second time, I WILL add H2SO4 to it. Again, anywhere from a few drops to a few ml should do the trick. The original gold was placer gold and not from escrap. I would expect that while it may contain some lead, I wouldn't think it would be that much.

The stannous test has always been a deep black. Both when testing my "standard" solution and my dissolved gold solution. Once I set the Q-tips down, they were indistinguishable.

If I follow Ms. Hoke, I need to evaporate more (at least once or twice). I can precipitate all that will come out right now, but if I wait for it to settle, and there is any nitric left, some will re-dissolve. As long as it's re-dissolving, there must be nitric. Get rid of the nitric and the problem should be solved. Dang, WHAT A ROOKIE MISTAKE!


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## Geo (Aug 27, 2013)

sounds like passivation. next time, pull the material that wouldnt dissolve and incinerate. most likely a layer of silver chloride covering the material. incinerating will allow you to break it up so the acids can reach the reactive metals.


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## butcher (Aug 27, 2013)

I can see several possibilities or where several different things could cause what you had, the key would be to troubleshoot and find out what the problem was.

When using NaNO3 in solution you are counting on having enough acid in solution, a portion of your acid (Hydrogen) is needed to form nitric in solution, and then you still need the portion of acid to form gold chloride, if you use too much NaNO3compared to the amount of HCl you can get to a point that not all of the NaNO3 is converted to acid HNO3 in solution, this can also limit the amount of acid HCl to form gold chlorides.

With the above scenario you can have a solution rich in NaNO3 unconverted to HNO3 in solution, as we know NaNO3 will not oxidize the gold, or be consumed by added gold or evaporation, evaporation would just concentrate the NaNO3 salts in solution, and adding acid HCl or H2SO4 at the end of the evaporation will convert the NaNO3 salts back into nitric acid.

So here we see we would need to have enough acid involved to convert all of the NaNO3 to HNO3 in solution, then we can vapor off nitric acid or consume it in the process with oxidizing our gold.

The stannous chloride test should show a violet color, if I get a test where it looks black (usually highly concentrated, I will normally hold the Q-tip in the vapor fumes of a solution of concentrating aqua regia, the fumes will normally dilute the black color and I will see the violet color of gold colloids on the Q-tip.

I also think as Geo stated it is possible your gold nugget (22K ?) button could have become passivated, which would keep gold from going into solution and consuming your nitric, or as above your acid was limited, so that there was not enough free acid in solution to dissolve the gold.
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Lets assume we have a solution of diluted gold chloride (no free nitric acid), no free HCl acid, but we have a dissolved salt of NaNO3 in solution,we test the solution and get a positive for gold in solution a violet color on our Q-tip, this proves to us that the stannous can reduce our gold back to metal (colloidal gold), now we go to precipitate our gold and we add our sodium metabisulfite to the solution, now lets look to see what could possibly happen when we try to precipitate our gold from this solution:

Sodium metabisulfite and water, form sodium bisulfite in solution:
Na2S2O5 + H2O --> 2NaHSO3

Notice the hydrogen in the sodium bisulfite above, the bisulfite can give up this hydrogen (and again form acid in solution) we we will see this below.

gold chloride and sodium bisulfite in a dilute solution to precipitate gold.
2AuCl3 + 3NaHSO3 + 3H2O --> 2Au (s) + 6HCl +3NaHSO4

Notice when we precipitate the gold we formed HCl acid again in solution, and also sodium bisulfate (which also has Hydrogen it could give up to form acid in solution), this is normal conditions so far.

The gas evolved normally breaks down the sodium bisulfate in solution into sodium sulfate, water and sulfur trioxide gas:
2NaHSO4 --> Na2SO4 +SO3 + H2O

Now what if we had NaNO3 salts in this solution, the HCl acid formed as we precipitate the gold mixed with the NaNO3 salts in solution would dissolve back the gold into solution.

HCl + NaNO3 --> poor-mans aqua regia
HCl + NaNO3 + Au --> poor-mans gold chloride solution


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## Harold_V (Aug 28, 2013)

A little tip. 
While it's not always the case, the use of natural nuggets for eliminating free nitric isn't a great idea, as the percentage of silver present will most likely result in a hard shell of silver chloride (which won't be white) surrounding the nuggets, quickly stopping the consumption of nitric. Beyond that, you will also have no idea of the amount of gold you've added to the solution (that may not matter). 

Use pure gold for eliminating nitric. 

Harold


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## bswartzwelder (Aug 28, 2013)

Thank you, ALL. I now realize there were more things to consider than just the original process.

Harold, if it makes any difference, the 22k 1 ounce nugget I used to try to eliminate the excess nitric was man made. It still doesn't rule out other contaminants since it wasn't pure 24k gold. 

While the small nuggets seemed to turn black, I would think it is possible there was some silver in there. Wasn't it in Nevada where the streams had a black deposit in them as a left over from the gold mining? After someone realized it was silver, I believe they found they had lost more money in silver than they had gained from the gold? I am also considering putting the very small black pieces from the original filtering into a crucible with flux and heating it in the microwave for about an hour. Whatever metals are present, should drop to the bottom when I pour the molten flux mixture into a cone shape mold. 

I will try and add a small amount of SMB to my solution to see if more gold precipitates. The precipitated powder that I got a couple of days ago seems to be a little bit lighter brown in color than what precipitated first. Could be my eyes playing tricks on me, I don't know. At any rate, not in a hurry, and will consider all suggestions.

As far as the white stuff which has been coming out of solution as I evaporated everything down previously, I believe I remember Ms. Hoke saying that a very little lead will produce quite a lot of lead chloride. I know I had WAY TOO much NaNO3 and SMB, so that's still my first guess. Lead is not an impossibility with placer gold. Again, thanks for all the input.


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## Harold_V (Aug 29, 2013)

In regards to the presence of silver when dissolving gold--if it is in a lower percentage (less than 10%), it will slough off and manifest itself as the familiar white material with which we are all familiar. However, if it's present in a high enough percentage, what it tends to do is turn a greenish gray color. At that point, it becomes impregnable by AR, and will tolerate being boiled for hours with no change. I know this from multiple experiences. I've not seen it turn black, but that may not be beyond reason. I'll withhold judgment, as I have no similar experience. It does, however, bring to mind colloidal gold, so I question if, maybe, there's a trace of tin in the gold button you mentioned. Even then, I'd expect that unless the free acid was well diminished, it would just be dissolved. 

Overall, it is my opinion that the man made gold nugget contained contaminants that are not in the best interest of the refiner. 

Harold


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## bswartzwelder (Aug 29, 2013)

I am still thinking I will melt the tiny black nuggets using flux. No one has said this will be a bad idea, and if it is truly gold underneath, little, if any, should be lost simply by melting with flux. Still working on the pyrolyzer when time and weather allows.


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## Geo (Aug 29, 2013)

any metal reclaimed by melting can be inquarted with silver and digested with nitric acid. it should clear up the problems your having with whats left.


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