2 Layers after precipitation, what is causing separation?

[Alentia]

After making my test run with 0.6 gr of 10K+ 0.1g of 18K gold and getting 0.32g of gold powder I have decided to run another test with 62 gram of 10K gold scrap.

1. I have reduced copper and silver by HNO3/H2O to the total of 38.79gr or 62.67% of total weight. Estimated net gold should be 62*417=25.85gr. Meaning I still had about 13gr of Cu and Ag, which would not dissolve.
2. Made 5 portions of AR (about 65ml +15 ml H2O or 80ml total)
3. Run 5 portions one at a time (one after another). Then combined all 5 solutions together.
4. Evaporated whole solution using H2SO4 and HCl
5. Added drop (literally) of Urea (no fizzling)
6. Diluted with 3-4 parts of distilled water and filtered. My solution is green/yellow I guess due to excess of copper.
7. Added SMB (not diluted in water), no fizzling. Gold started to drop slowly.
8. Got precipitated gold at the bottom


I have 2 questions:

1. Why am I getting 2 layers of liquid? One is yellowish at the bottom and second is above - teal (with copper) with separating ring, which looks like AgCl or something else floating in between layers?
2. During 5 staged AR additions, I used temporary container - volumetric flask. I have gold residue on inside walls. How do I get it out? Shaking with AR?

I have encountered another issue:

On my 5th run with AR, very little gold was remaining, My pyrex beaker cracked on me and all solution went into my sand bath. (I did not add this solution to my main solution)

1. I have picked sand, dropped it in AR, added water and boiled for few hours
2. Filtered
3. Added water and reboil
4. When I dropped bit of H2SO4, white stuff started to form and after adding little bit of HCL it looks like gelatinous chloride.
5. Added hot water. I have separate a bit of liquid from main beaker and tested. Liquid tests negative for gold with Stannous. SMB simply dissolves in the liquid nothing drops. I am guessing there is gotta be something in that white gelatinous mass.

I understand I got some kind of reaction with Si Au and AR and whatever salts were in the sand. Sand was from Dominican beach. I doubt there was Pb in the sand. What did I get? There might very well be about 0.2-0.5gr of gold. Is there a way to break that gelatinous stuff or it is not worth it? This is more for the discovery and interest.

 

[butcher]

I am not sure this will give answers, but here is what I think.
I believe the sand would have base metals (like Iron) that could cement your gold out of solution, and these would need to be removed to get the gold, I would incinerate the sand as they may also contain sulfides or other mineral/metal salts, and leach base metals before trying to extract the gold (if there was enough gold in this to make it worth the cost and trouble).

Some times you will get layers in chemical reaction for several reasons, like dirt, oil, or organics in solution, reactions not completed, not enough reagents, or even too much reagents, other reactions in metal solutions like a base metal in a gold solution, or even metals like tin that will not completely dissolve but will jell up, colloids in solution.

I would try a strong heating and make sure acid content was high and then see what happens.

 

[Alentia]

Thank you, Butcher!

I am not sure this will give answers, but here is what I think.
I believe the sand would have base metals (like Iron) that could cement your gold out of solution, and these would need to be removed to get the gold, I would incinerate the sand as they may also contain sulfides or other mineral/metal salts, and leach base metals before trying to extract the gold (if there was enough gold in this to make it worth the cost and trouble).

There is no more sand, it is the "white jelly" and liquid with no gold in it. Is there anything in the "jelly"? and what exactly can I do with it?

I would try a strong heating and make sure acid content was high and then see what happens.

You mean HCl, correct? You mean boil the solution with dropped gold inside or filter first and then boil?

 

[butcher]

??? Are you saying you completely dissolved the sand into that white gel???
What and were did this sand come from?

Well sand usually has a high percentage of (quartz) silica (what they make glass from) and that usually will not dissolve in the solutions we are discussing, sand is also small rock or ore, I suspect your sand is not what I think of as sand. if there was gold in it then there still should be gold in it, if the solution tests negative (a negative test can be for several reasons), if you have nitric acid (or other oxidizer) in your solution you are testing for gold, you will not get a positive reaction as any gold that was trying to react with the stannous chloride to turn colors would just re- dissolve and give you a false negative reading of your test, or another reason for negative test could be your testing solution is not working (test your test solution with a known gold solution) and then a negative can mean there is no gold in solution. In that case it should be in salt form, (usually as black or brown powders).

Cementing with copper buss bar if gold is dissolved in solution,
Or if in powders try and get it into solution if possible then separate it from the junk that will not dissolve then cement gold back out of solution onto copper.

I was talking about colloids in solutions (they are like two electrons neither negative or positive fighting each other and holding each other in suspension)
Heat and high acid content sometimes helps to break colloids< I am not positive that is what you have but it is worth trying until someone else give you better clues, boiling is not necessary just heat below boil for a while this will also concentrate solution raising acid concentration, I would probably add some HCL also.

http://mysite.du.edu/~jcalvert/phys/colloid.htm

http://en.wikipedia.org/wiki/Colloid

 

[Geo]

what material did you start with? was it E-scrap or black sands concentrates? if it was E-scrap the white "sands" could be tin (II) chloride which you have turned into metastannic acid.that could be the white gel. at least that's what it looks like as for the separation someone else will have to comment on that.

 

[Alentia]

It was just regular 10K gold scrap jewelry.

After vigorously stirring the solution the layer is gone. It looks like the separation was made of trapped bubbles of SO2.

 

[dtectr]

Just my random dos centavos -
Beach sand (from Dominican Republic or Dominica?) would of course be contaminated with sodium chloride, also possibly iodine from seaweed (kelp), both solvents for gold, under the right conditions. I doubt if either would survive the extensive processing, though?
Coral sand and/or sea-shell sand would be calcium-(what? carbonate? anybody?)

I was going to suggest, though it seems you figured it out, That a concentrated dirty, solution could create layers of varying densities. lazersteve recommends diluting auric chloride by double, up to quadruple; he suggests it primarily for forcing silver chloride out of solution prior to filtering, then precipitation.

NOTE: I hope this (following) isn't viewed as a hijack - the images illustrate my thoughts, and i believe it to be relevant:

I've postulated on this before, Hoke stated that sulfur dioxide (produced by reaction from SMB) is best used on neutral, or slightly acidic solutions. The common practices used by many members, i.e. super-dilution, packing with ice, etc. - wouldn't they serve to raise the Ph to nearer neutral, making sulfur dioxide more effective? Wouldn't it also lower the risk of drag-down?

Forgive my ramblings - I've caught my annual virus and feel like, well, you know. I'm gonna take my meds & go back to bed.

keep us posted & good luck <<groan>>
edit: typos

 

[samuel-a]

Looks like Orthosilicic acid or some other member of the Silicic family.. :mrgreen:

but that's just a shot in the dark...

 

[Alentia]

Now I have hit another interesting issue.

After precipitating gold from the solution, the solution came out to be very clear light green color.

1. I have added too much SMB as solution have strong smell of sulfur when siphoned to another vessel
2. Solution was sitting with SMB for 48 hours and I should assume 99.9% of gold has precipitated
3. Test with 3 days fresh stannous is negative (keeping it in dark glass bottle) actually resulting in "yellow" color, which I should attribute to "iron", if correct.

Now, when I add "Salt"not ionized to the solution I do not have AgCl dropping down. Salt got dissolved and that's it. As per previous calculations I suppose to have at least 13gr of contaminants: silver, iron and copper. Based, that my solution is green, looks like majority of it is iron. It is possible to think that solution is green because of "yellow Gold" and "Blue Copper", but as it was with SMB for 48 hours, gold is precipitated. But, I might be totally wrong!

What is causing AgCl not to drop, other then absence of it in the solution. Could it be that too much SMB won't let AgCl precipitate?

 

[butcher]

Silver or AgCl is insoluble in these acids, (so basically it will not be in aqua regia).

Very little silver can form AgCl2 this little bit of silver salt may carry through your process until you dilute the acid, at that time it becomes AgCl and precipitates as white silver chloride salt.

You may not have had much silver in solution.

Too much SMB and other metal contaminates could give a yellow solution (I think Iron?).

I believe the silver would precipitate even if you had an excess SMB, and even could form silver sulfate depending on how much excess we are talking.

It seems you may have some base metal contamination and an excess of reagents.
Very good post dtectr, very good thinking on that sand (I guess I just think of river sands), one point I would like to make, adding water (dilution) will not change PH, that is a function of (adding) acid or basic solutions, water is neutral, so it just gives the acid or base ions more room to move around.

Percentage of hydrogen is PH, in water the Hydrogen and oxygen are bonded very strong (if that’s what they call it). water can be separated with electrolysis into hydrogen and hydroxides, but normally will not separate.

 

[Alentia]

Thank you, Butcher for enlightening! What am I thinking... I have already deposited all AgCl into my AgCl container from AR. I guess I am left now with Cu and Fe in the solution and whatever else might have been there like Zn, Pb and Sn. Solution is emerald color.

On another thought about sand boiling in AR. Could it be that gold got precipitated by the sand and now is in the sand, when beaker cracked? The white stuff I got is possibly by product of sand salts and gold precipitation... could it be? Can sea sand precipitate gold?

 

[butcher]

I do not know about the ore in sand in your beach, but sand around here can contain metals, metals can precipitate gold from solutions, also the ore may contain other anions (like sulfates) this could make an iron sulfate and precipitate gold, sand or ore can be very complex mixes of anions and cat ions, some like manganese dioxide in ore if mixed with HCl will even dissolve gold, where HCl alone will not.

 

[qst42know]

Sands from a salt water beach are likely to have coral and shell origins and as such big consumers of acids.

What is the PH of your solution?

 

[Alentia]

I do not have litmus paper to identify solution PH, but it looks like alkaline at or above 7. Sodium Hydroxide is not causing any immediate reaction. Looks like that "white stuff" consumed all the acid. The sand is full of organic matter like microscopical pieces of shells, etc.

I have strong feeling that my gold has precipitate into the sand in tiny particles. Are there any known method to get it out of there?

 

[Alentia]

After all I got 25.11 gram of gold powder, which I assume should be 99.8-9% pure. This falls short of initial estimate of 25.73 by 0.62 grams. I am guessing my calculations of loosing about 0.3-0.5 gr in the sand is correct. The rest is attributed to ~ gold content in 10K jewelry. So the question remains, how do I recover gold from sand I have used for sand bath.

Will use water bath next time...

 

[Harold_V]

So the question remains, how do I recover gold from sand I have used for sand bath.

I'd suggest a start with nothing more than a water rinse. If the resulting water tests negative, it's likely the gold has cemented on something within the sand in question. You may or may not be able to make a recovery that is economical. You may be well served to consider this a part of your cost of learning and move on. My logic is that if the gold has cemented, you're likely to be troubled by the substance(s) that cemented the gold, which will make recovery difficult, if not impossible.

In all my years of refining, I never used a water bath or a sand bath. I used thin asbestos gauze or sheets between my heat source and the beakers I used. When they became dysfunctional, they were sent to my waste materials for processing for traces of values, which are sure to be present, just as the sand you speak of.

If you have plans for furnace work at some point in the future, you may wish to consider adding the sand, along with soda ash and borax, to a charge. The soda ash will dissolve the sand (assuming it's silica) and liberate the traces of values. If you have a collector present, you should recover the vast majority of the gold tied up in the sand. The negative here is the potential to include something that complicates processing of the recovered values, but that was never a problem for me.

Harold

 

[Dr. Poe]

Before I tell you what I think, let me tell you what I've had in the past. I had the very same accident with the same results. I dried the white flakes and cupelled them with lead. The product was 23+K gold. It turns out that boiling with H2SO4 to fumes produces SO2 gas which precipitates gold, but that wasn't why it happened. When H2SO4 is boiled with silica sand in the presence of sufficient water a substance is produced that is a hydrated silica oxide. This oxide hydrate is exactly the same formula as is oxallic acid except that silicon atoms substitute for the carbon atoms. The action on soluable gold salts is almost the same except SiO2 is formed and precipitated with the gold instead of CO2 gas. Often Leaching from sand with strong acids will dissolve some Silica as well. Hindsight is 20:20 but it's always better to check your glassware for cracks.

 

[samuel-a]

Looks like Orthosilicic acid or some other member of the Silicic family.. :mrgreen:

but that's just a shot in the dark...

Before I tell you what I think, let me tell you what I've had in the past. I had the very same accident with the same results. I dried the white flakes and cupelled them with lead. The product was 23+K gold. It turns out that boiling with H2SO4 to fumes produces SO2 gas which precipitates gold, but that wasn't why it happened. When H2SO4 is boiled with silica sand in the presence of sufficient water a substance is produced that is a hydrated silica oxide. This oxide hydrate is exactly the same formula as is oxallic acid except that silicon atoms substitute for the carbon atoms. The action on soluable gold salts is almost the same except SiO2 is formed and precipitated with the gold instead of CO2 gas. Often Leaching from sand with strong acids will dissolve some Silica as well. Hindsight is 20:20 but it's always better to check your glassware for cracks.

Bullseye 8) :mrgreen:

 

[core]

Wow! This is beginning to make more sense to me. I am working with an ore that has undergone these conditions naturally (I think). The veins from an oceanic plate convergence in the country rock are filled with what looks like beach sand at this particular formation. Hot concentrated sulfuric acid solution being shot into seawater of an ancient shallow sea.

Ive been stumped as to why I can drop au from solution with smb or oxallic acid and everything goes as expected untill the wash cycles. Then a white powder appears. I can dry the powder and heat it slowly as it changes into the yellow, red, then brown au metal. Only upon melting it just wont stick together. You can see the characteristic green associated with gold mixed with glass.

I can fuse it to lead, but it seems to be absorbed into the cupel and also certain melting dishes that Ive bought.

I think that im gaining on it though, having cemented with copper and am trying to refine the powders. I have determined that tin is present as well as chromium causing me hassle. I have DMG on order and is due in any day so I should be able to determine nickel and palladium being present soon.

I have had two assays from seperate companies that both seem inaccurate to me; They don't resemble one another and show no preciouse metals from fire assay, ICP, or XRF. I dont really want to go into my experiences with assayers to much. I may have ordered the wrong type of test for my materials this last time, but neither time were the folks very helpful even though I tried to explain. Im not laying blame, I just want a good job. This is complex and mistakes do happen.

Upon cementation with copper tubing- I see a couple of different shades of silver. A third shiny one (hg) and then gold will cover that. There are definately values present.

Throughout these bench tests that I have done, I tried incorporating activated carbon to catch colloidial gold solutions. I also experimented using it as the cathode in a cell. Last night I incinerated all of it and chose to begin new process with a fairly concentrated- hot naoh boil in an iron skillet to eliminate carbons and chromium first. The results of that production was blood red salt water, and the same for a second clean water rinse.

So, I think It is leaching the Au from the mix which would be great providing I can find a way to recover it. I seem to recall reading somewhere here how to break the colloidial solution of au in naoh, but I cant find it again. Can someone help me out with this?

And also Could you elaborate more on the reaction of Au being precipitated by siO2? How or what can I do with this? The AU will go into solution with just hcl and after a time and the reaction slows and a small nip of bleach is added.

Ive decided to have one more assay performed and have been referred to a reputable firm. What is the most sure way for me to pre process this material and what type of assay should I order? I was thinking of sending just the cemented values from the stock pot. Im not sure what to classify this ore as- an Oxylate? Chlorite-ate? Sulfide refractory or double refractory? I would like to know the base metals present as well. A four acid assay perhaps?

Im really thankful to you all for the posts from the past, present, and future. Im learning new fascinating things here everytime i log in, and have come a long way from where I began almost a year ago. Thank You for your patients and attention.

Core

 

[butcher]

core,
It sounds like you are trying to leach an ore.
Ore can be a wide variety of metals, and can be sulfides,oxide or a number of other an anion, basically rock can be a complex mix, and there are many different mixes to make up different types of rock.
leaching may not always prove successful, and in fact many times you could end up spending a lot of time, money and acids leaching just the base metals from the ore and not touching the values, also to leach the gold or even the base metals many times you would have to put them into a state that the acid would dissolve them, sometimes roasting will drive off sulfides (sometimes iron is needed in the roasting process, before the acid can attack the metals bound up as sulfides, sulfide ore is very common but it is not the only type of ore, halides, oxides, hydroxides, nitrates, sulfates, chromates, molybdates, tungstates, phosphates, arsenates, vanadates, silicates, and even organics, basically the ore can be compounds of very complicated chemistry, and so can the chemistry when trying to leach, the rock can change the chemistry of the acid, the metals in the ore can be in a state that the acid cannot dissolve, basically leaching may or may not work at all, and normally even if the acid leach will work the ore needs pretreatments to put it into a state that the acid can leach it.

Usually the ore will also need concentrating the values, before most any kind of extraction process is used (concentrating the more valuable metal, separating it from the bulk of the gangue ore).

Knowing the chemical make up of your ore would be important to help you determine a method for extracting values.

But most important would be a good assay to see if there was even enough value to try and recover, not an assay of concentrated material, but an assay of the whole mining area, so that you know how much values per ton, of the whole lot, not just sweet spot or of a good looking stone.
If you pick a stone that looked promising and sent it in for assay, say it had visible gold and got you exited to mine the area, now this assay of this stone shows high gold content (as it should you looked hard to find that one rock that would), but the most of your mining area is barren of gold, now your mining tons of rock spending money and getting nothing in return (all based on one good looking rock) the ore sample should be a wide mix of a Representative sample of the are your are planning on mining.

Working with ore and working with more pure metals in solution are completely different ball games.

You state your gold is will go into lead, but when you cupel the lead the gold goes into the cupel with the lead oxide (that is not gold, but an oxide).

you also mention your gold when melted will not stick together or You can see the characteristic green associated with gold mixed with glass. Again this does not sound like gold but an oxide.

Note working with Ore and acids can be dangerous, again knowing the chemistry of your ore can be important, you can easily gas yourself to death pouring acid onto an ore that was an arsenate compound of ore.

Also treating your waste solution and disposing of it properly and safely, without concentrating your values, you could use tons of acid to get a speck of gold and have tons of toxic waste on your hands.

If the gold was free gold mechanical means to get it would be my choice, if the gold is bound up in the ore, either mining and selling the rock or just forgetting it and moving on and finding a place I could mine free gold would be my next choice.

You are not likely to do much good leaching ore,