# What can make the hcl/cl solution yellow before adding cl?



## electric (Feb 29, 2012)

Hello, title is pretty much my question. 

I am wondering what can possibly make my hcl turn yellow, before even adding the bleach? I am doing a stannous test on some concentrate and I skipped the acid/peroxide part figuring it would still show purple regardless of other stuff that might be in there. Just trying to save the cost of the peroxide in case my result is negative. So I simply put a pinch of the concentrate in a small amount of hcl and it turned a banana like yellow before even adding any bleach. It did turn a deeper gold tinged yellow once the bleach was added though. (I'm still waiting on my stannous chloride, doing the solder method) 

Just wondering if that's a dead giveaway that you guys may know about. Is there anything well known to cause pure hcl to almost instantly turn yellow? I'm assuming this is the sort of "unknown" stuff you want to get rid of beforehand with AP when doing a larger volume of material. Could it simply be anything because of my concentrate not being quite so pure? (it's been panned as much as I could but what I have is very ultra fine particles of what I think may be gold. I think you guys call it flour gold.)

Thanks.


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## Geo (Feb 29, 2012)

have you used any form of nitrates on your concentrates before doing this part or could any have gotten mixed in? such as fertilizer? tin will color hcl yellow somewhat.


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## lazersteve (Feb 29, 2012)

Iron comes to my mind first. Iron easily dissolves in HCl and colors the acid yellow to dark orange in higher concentrations.

Steve


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## maynman1751 (Feb 29, 2012)

I have noticed that my Hcl (muriatic) acid has a yellow color straight out of the jug!


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## dtectr (Feb 29, 2012)

What form is the concentrate in? Black sands or gold flour? If it is elemental gold it will look gold. He it is black sands, it can be almost anything. As geo stated, tin oxide can turn it bright yellow, Manganese is readily soluble in HCl, appearing anywhere from yellow to orange- brown, depending on degree of contamination.
What have you done to process this, besides panning? If nothing then you need to a lot of research esp butcher's posts on the subject. 
Chlorination of ore as a means of gold recovery is inefficient, even on properly roasted and milled ore, yields of over 85% are extremely rare. What you do manage to recover will be heavily contaminated by base metals, esp if you use HCl. Successful operations in australia, for example used dry chlorinating powder with H2SO4 as the oxidizing agent.


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## electric (Feb 29, 2012)

Thanks for the quick replies. 

Nope, no nitrates of any form. 

But a stannous test would still show purple if there is any gold at all in the solution, correct? Or would the iron for example throw off the color result of the test?

here is my first thread with pictures of what I'm dealing with (scroll down to mid post) http://goldrefiningforum.com/phpBB3/viewtopic.php?t=12558

it's a muddy type stuff, but what I am attempting to test with is the most water treated/refined stuff I've got (ie what has gone through the most cleaning steps). What is potentially the gold is just so small that I can't really pan it in the traditional sense, so I've got some other impurities in there as well.


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## Geo (Feb 29, 2012)

if gold is in solution, the test will show positive regardless, unless it was saturated with iron and then you might get a false positive.


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## goldsilverpro (Feb 29, 2012)

maynman1751 said:


> I have noticed that my Hcl (muriatic) acid has a yellow color straight out of the jug!



Muriatic is just cheap impure hydrochloric acid. Iron is the yellow and it is a common impurity in some muriatic. I wouldn't worry about it.


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## maynman1751 (Feb 29, 2012)

goldsilverpro said:


> maynman1751 said:
> 
> 
> > I have noticed that my Hcl (muriatic) acid has a yellow color straight out of the jug!
> ...


Thanks GSP. I wasn't concerned about it. I just brought it up suggesting that might be the yellow that he is seeing....or not.


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## lazersteve (Feb 29, 2012)

maynman1751 said:


> I have noticed that my Hcl (muriatic) acid has a yellow color straight out of the jug!



Iron is a common contaminate in low quality muriatic acid as an iron compound is used in the manufacturing process. Higher grade HCl does not have this problem. Sometimes the yellow color shows up after the jugs are stored for a while.

Opps!

Sorry GSP, 

I didn't see your reply above.

Steve


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## Traveller11 (Mar 1, 2012)

dtectr said:


> What form is the concentrate in? Black sands or gold flour? If it is elemental gold it will look gold. He it is black sands, it can be almost anything. As geo stated, tin oxide can turn it bright yellow, Manganese is readily soluble in HCl, appearing anywhere from yellow to orange- brown, depending on degree of contamination.
> What have you done to process this, besides panning? If nothing then you need to a lot of research esp butcher's posts on the subject.
> Chlorination of ore as a means of gold recovery is inefficient, even on properly roasted and milled ore, yields of over 85% are extremely rare. What you do manage to recover will be heavily contaminated by base metals, esp if you use HCl. Successful operations in australia, for example used dry chlorinating powder with H2SO4 as the oxidizing agent.



If a person removes all black (iron) sands from his concentrate, either with Neodymium rare earth magnets or HCl, and then thoroughly filters and washes the concentrate to remove all of the iron in solution, will this improve the efficiency of the HCl/Cl process? I do not think there is much else in my concentrate that is metallic, other than pyrites. Will the HCl dissolve pyrites?


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## Harold_V (Mar 2, 2012)

Traveller11 said:


> Will the HCl dissolve pyrites?


Not in my experience. I had a large volume (about ten gallons) of (crushed and screened) pyrites loaded with gold. The only thing I found that worked was to roast the pyrite, then to digest in HCl. Repeated the process until all of the pyrite had been digested. Surprisingly, even when roasting to a dull red heat, I had to repeat the process about three times, each time showing obvious signs of sulfur being consumed. Once digested, I even had a small sulfur fire when introducing the material to the heated sheet of stainless. In the end, the approximately ten gallons were reduced to about a quart, which then willingly gave up the gold. Don't recall the amount now, but more than five ounces. 

Harold


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## Traveller11 (Mar 2, 2012)

Thank you for that answer, Harold.
I guess the next logical question is, if the gold in the concentrate is all microscopic free gold, will the pyrites interfere with the HCl/Cl process?
Also, for HCl to dissolve iron, for the purpose of removing it from the concentrate prior to dissolving gold with HCl/Cl, is an oxidiser required or does the HCl dissolve iron without it?


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## Harold_V (Mar 2, 2012)

Traveller11 said:


> Thank you for that answer, Harold.
> I guess the next logical question is, if the gold in the concentrate is all microscopic free gold, will the pyrites interfere with the HCl/Cl process?


In my opinion, yes. The gold was free in the material I processed, but sulfides complicate things. I even tried cyanide. I could dissolve some gold, but it readily precipitated when I'd allow the material to settle. I ascertained that fact by taking dip samples and filtering immediately. Gold reported in the cyanide when it was rapidly filtered, but absent after the tank was allowed to settle. 

Not being a chemist, I had to experience many of these things before they made sense to me. That's why I'm replying with comments as my opinion. I don't have the credentials to speak with authority. 



> Also, for HCl to dissolve iron, for the purpose of removing it from the concentrate prior to dissolving gold with HCl/Cl, is an oxidiser required or does the HCl dissolve iron without it?


Indeed it does! HCl is an excellent solvent for iron. It's used to pickle iron, in fact. However, as a sulfide, it didn't appear to have the least bit of solvent capability. You could probably achieve some degree of success with AR, but that's a nasty way to approach recovery. The resulting mess is far more trouble than eliminating the sulfides at the outset. You are very best served by eliminating the sulfur. 

Harold


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## butcher (Mar 2, 2012)

Traveller11, 
I am adding this edit to this post, I made a mistake after posting it seems I glanced at electric's photo and thought it was what you were discussing, so unless your gold looks this clean disreguard this post, as it is based on very little pyrite or black sand in the gold.

From looking at the Photo, of the gold in your other post, you panned, it looks pretty well cleaned up, and I do not see where you should have much trouble refining it.

If it is indeed gold, which form the pictures appears to be, I have to admit, I did not read the thread, and just glanced at your picture before writing this, and am not sure if this is from a hard rock operation or placer gold.

My comments here are based on a very low content of pyrites, or black sand, and well panned free gold, and assuming placer gold although if cleaned well would not be terribly different.

As too high and Iron content (or other base metals) can mess up our solutions or process, and would need leaching before trying to dissolve the gold,

From glancing at the photo, yours looks clean.


I think I would roast it just for the heck of it, 

If you can get nitric acid, then treat it in nitric acid wait a few minutes to see how it reacts, then add heating it to a good hot solution, the gold looks to be very fine, so if there is silver involved, a good stirring, you may get it into solution, some placer gold is 16% to 18% gold, and could have some silver to give you trouble dissolving the gold later, so for larger nuggets quartering the gold with silver may be needed, before treating in nitric acid, your gold looks so fine I think you may not have a problem there, but quartering may be necessary.


I do not think you will have too much pyrites in this, as if this gold was panned down to what looks to be fine gold in your pan, the pyrites are light and would have panned out way early in the panning process, the pyrites are so light they will pan away before much of the other dirt rock and sand, black sand,
Gold is very heavy (even very fine gold), and is the last to be panned away, the black sand can be iron oxide compounds magnetite and hematite, from looking at the picture of your pan I did not see much black sands, and as long as you do not have too much then you should not have trouble here.

Be careful not to breathe fumes from any processing, and extremely cautious of fumes from ores, as acids on some types of ore can emit extremely deadly gases.

I noticed your question about the hydrochloric acid and sodium hypochlorite, and I am wondering if you are trying to dissolve your gold in it without treating with nitric acid first, (if you do not have nitric acid you could try it), the gold if as fine as it sounds, it may go into solution with some heat, without pretreatment of nitric, but if You can get nitric I would use it, I would not skip the incineration step though.

I do not see where a very small amount of black sands, or even pyrite (especially as it seems you have cleaned your concentrates of these so well, would give you any trouble dissolving your free gold, the little bit of these may give up some iron in solution, but it is hard to break their bonds easily (iron sulfides, or iron oxides), and just a little of these in solution should not give you any trouble, even if some iron did entered into the solution.

You may find the gold will not dissolve easily into HCl/NaClO if silver content is high.

Also I mentioned Heating the solution, keep in mind that Chlorine will not stay in a hot solution very long at all, so you really do not need to get it too hot, and you may need to add sodium hypochlorite more often and in small amounts (the solution will work in room temperature but will just take longer), actually chlorine will stay in a cold solution much longer, (kind of a double edge sword).

Remember also when testing with stannous chloride for gold in solutions you will need to eliminate the free chlorine in the portion of solution that you are testing, or you may not see a reaction if the chlorine re-dissolves the gold in your test.

Also free chlorine needs removed before trying to precipitate the gold.

P.S. take Harold’s advice over mine any day, I cannot see your gold, and I am not sure Harold has looked at your photo, also it is kind of hard to tell what actually is in a picture, 

Edit oops I wrote this post based on looking at the wrong gold or picture.


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## electric (Mar 3, 2012)

Thanks alot for all the advice butcher. Very much appreciated. I don't know where and if I can get nitric acid (I'm in Canada), but if I can eventually find any, I will try as you suggested. 

It might be worth adding that I tried going over my concentrate with a fairly strong magnet and virtually nothing was attracted by it. Maybe not the right type of magnet, I will look into that. The hydrochloric acid still turned yellow pretty fast, so either it was something other than iron turning it yellow or my magnet was not up to the task...? 

I'm gonna go search the forum for roasting now as I'm not sure exactly how it's done.


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## Traveller11 (Mar 7, 2012)

electric said:


> Thanks alot for all the advice butcher. Very much appreciated. I don't know where and if I can get nitric acid (I'm in Canada), but if I can eventually find any, I will try as you suggested.
> 
> It might be worth adding that I tried going over my concentrate with a fairly strong magnet and virtually nothing was attracted by it. Maybe not the right type of magnet, I will look into that. The hydrochloric acid still turned yellow pretty fast, so either it was something other than iron turning it yellow or my magnet was not up to the task...?
> 
> I'm gonna go search the forum for roasting now as I'm not sure exactly how it's done.



It seems that the Neodymium N42 and N52 magnets will attract hematite from concentrate as well as the magnetite that other magnets attract. Google "K&J Magnetics" and you will find a site with a wide selection of these magnets at very reasonable prices. I would tend toward the N52 magnets as I have heard far more evidence of them attracting hematite than I've heard for the N42 magnets. 

Just be careful that gold particles don't get "entrained" with black sand particles being drawn by magnets. One way to avoid this is to attach an orbital sander to the bottom of your panful of black sand and water. The vibrations should drive the gold to the bottom of the pan, hopefully out of the grasp of departing black sand particles.

Bob


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## Traveller11 (Mar 9, 2012)

Further to the HCl/CL process, I have another question regarding safety. I know, so far, that adding sodium (calcium) hypochlorite to hydrochloric acid will cause chlorine gas to be given off. However, I read on another site that adding sodium metabisulphite to the pregnant solution derived from this process will also give off a harmful gas. Is this true? If true, what is the gas given off?

I have been looking at full faced respirators (acid protection, as well) with interchangeable cartridges. Before I purchase one, I would like to be sure I can find a cartridge for it to protect against other gases, as well.


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## publius (Mar 9, 2012)

Traveller11 said:


> Snip: I read on another site that adding sodium metabisulphite to the pregnant solution derived from this process will also give off a harmful gas. Is this true? If true, what is the gas given off?
> 
> I have been looking at full faced respirators (acid protection, as well) with interchangeable cartridges. Before I purchase one, I would like to be sure I can find a cartridge for it to protect against other gases, as well.



I post warnings about respirators because:
1... I wear one every working day on my "day" job. It has been fit tested and it is well maintained. I have access to any replacement cartridge required. Engineering controls have failed to reduce the hazard I am exposed to to below the PEL...
2... I was certified to fit test my shipmates when I was in the US Navy some 16 years ago.
3... I have seen friends die or seriously hurt when using improper or ill fitting respirators.
4... I study this subject so that the misinformation can be countered with facts
5... No negative pressure, filtering respirator will protect you from all hazards.

The gas given off (I will be corrected if I am wrong) is SO2 or sulfur dioxide. It is harmful/deadly in concentration (PEL = TWA 5 ppm (13 mg/m3)) Permissible Exposure Level over a Time Weighted Average (8 hours) is 5 part per million. But it is considered deadly (IDLH) at a concentration of 1000 PPM

OSHA (not applicable if you are a hobbiest) requires that engineering controls be applied before personal protective equipment [PPE] (a respirator in this case) are used. That means that a fume hood or working outdoors should be done before thoughts of PPE are conjured up.

Generally speaking, all the forum members advise that any chemical additions be done in tiny doses for at least 2 reasons, economy and safety. Some additions can be energetic and some produce hazardous gasses or vapors. Tiny additions of SMB to your ACl will never bring the amount of SO2 in the air you breath any where near the 5 ppm especially if you are working out side or with proper ventilation.

[/soapbox]


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## Geo (Mar 9, 2012)

dont stick your nose in your reaction. curiosity killed the cat.


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## bobinpasask (Mar 14, 2012)

publius

Excellent post on the respirators. I work them them all the time as a consultant and teach respirator use with Asbestos and Molds. Have seldom thought of their use much with a gas such as you mention, so even a 65 year old dog can learn new tricks.

I've never seen so much said about respirator use in such a short paragraph. Well done. You are the first person in milllions of written words I've read that has used the "engineering controls" wording and also in the proper context. Spot on .

People need to understand that engineering controls are mechanical or physical means of dealing with a problem (like the gases being relased that you discuss). Try a fume hood, work outside, even a fan blowing out a window and taking the gases with it. Anything to physically solve the problem BEFORE just standing there with a respirator on. 

As a summary to your post. Please Use PPE as a last resort !


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## publius (Mar 14, 2012)

bobinpasask said:


> publius
> 
> Excellent post on the respirators. I work them them all the time as a consultant and teach respirator use with Asbestos and Molds. Have seldom thought of their use much with a gas such as you mention, so even a 65 year old dog can learn new tricks.
> 
> ...


Thank you, sir! I try.


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## Traveller11 (Mar 15, 2012)

Yes, thank you for the words of wisdom, Publius. As well as the respirator, I was planning to use this process outdoors on a bench I have set up under the overhanging roof of my shop. As an added precaution, I plan to set a fan up beside me to create an air current. Do you think it would be best to have the fan blowing fumes away from the reaction or drawing fumes toward the fan?

I was also looking at a site describing the "Igoli Process" which was developed in Africa in an attempt to get small miners away from using mercury. The Igoli Process is essentially the HCl/Cl process although they have added a few things. Instead of allowing chlorine gas to go straight into the atmosphere, the leaching vat is sealed and the chlorine gas comes out of the vat through a tube on top of the vat. The tube is fed into another sealed container containing sodium hydroxide and, it is claimed, the chlorine reacts with the NaOH and becomes salt. It is unclear if the chlorine gas travels from container to container on its own or if it has to be drawn by vacuum.

The people behind the Igoli Process claim it is necessary to stir the concentrate occasionally though they do not say anything about adding air. They have an interesting filtering chamber for separating the pregnant auric chloride solution from the concentrate. It relies on low air pressure and one of their photos shows a fellow with a bicycle pump providing the pressure.

This company will build a custom leaching unit for the small miner or will provide the technical info free of charge. I wrote to them in Africa in February but have yet to hear back from them.


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## Traveller11 (Apr 28, 2012)

butcher said:


> Traveller11,
> I am adding this edit to this post, I made a mistake after posting it seems I glanced at electric's photo and thought it was what you were discussing, so unless your gold looks this clean disreguard this post, as it is based on very little pyrite or black sand in the gold.
> 
> From looking at the Photo, of the gold in your other post, you panned, it looks pretty well cleaned up, and I do not see where you should have much trouble refining it.
> ...



Well, I got my respirator mask in the mail with the cartridges for chlorine. I set my first experiment up outside my shop on a bench with a fan to blow fumes away from me.

The first thing I did was place a small amount of black sand (almost pure magnetite) in a plastic dish and cover it with Muriatic acid (HCl). The acid was a very light shade of yellow as it came from the bottle. After a few minutes with the black sand, the acid became a deeper yellow and then a dark orange. Going by the information in this thread, I would assume I am seeing iron being given up from the magnetite although, at a glance, the magnetite appeared to be intact.

I'm wondering if I should drain off the solution through a filter, wash the magnetite with water and try covering it again with Muriatic acid. Is it possible some iron was liberated but the remaining magnetite is stable? And, if I go to the next step, HCl/NaClO leach, will iron not dissolved by the HCl go into solution with the addition of NaClO?


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## butcher (Apr 29, 2012)

I would have roasted off the sulfide getting it red hot grind and re-roast, the iron will leach yellow at first and also green, it will take several leaches (saturated with iron), these can be decanted and fresh acid used to dissolve more base metal, heat also helps but too much heat can form iron hydroxide, which will not dissolve in acids, I use 3% H2O2 also with the HCL, if you have gold it will be left as brown powder or minute flakes of gold.

Normally if gold is in black sand it is easier to just pan it out.


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