# Thiosulfate Questions and Discussion



## dev

Hi everybody, this is my first post here so before I do anything else I want to offer massive thanks to the contributors that make this forum such a great learning resource. I've been lurking and learning for a while and I very much appreciate both the excellent information and the attention paid to safety.

With apologies, I'm an ore guy, and a newbie hobbyist one at that. I'm here instead of a prospecting forum because I prefer the pragmatism of the people here, as opposed to the rather starry-eyed, excitable folks that see El Dorado at every river bend.

My interest at the moment is in Sodium Thiosulfate Pentahydrate: Na2S2O3.5H2O. I'm trying to use it to get past the wall of iron between me and the values in the dirt I'm playing with. I first did an Iodine leach/copper drop with this ore and was able to collect several grams of values -mostly silver, looks like- from just a couple pounds of ore. Still have no idea what's really in there, but I figure any visible cementation on copper, from such a small batch, is at least worth exploring further.

After using iodine as my 'assay' leach, I experimented with HCl/Hypochlorite (Clorox), and for my trouble I got iron, and more iron. And of course this also left most of the silver in the ore as silver chloride. So, on to Sodium Thiosulfate in the hope that its greater selectivity will beat the iron problem.

I got a surprise when I set up my first thiosulfate leach. I knew the pH should rise as hydroxide is produced. Instead, it gradually dropped at the rate of about a full pH point every 12 hours. From pH 9.8 to pH 8.6 overnight. Well, nobody said this was gonna be easy. 

I expected that the leach would signal thiosulfate depletion when the pH stopped rising. Since it doesn't rise at all, I have no indication of the status of my leach. Which leads me (finally) to my reason for posting. Can anyone suggest a means for checking thiosulfate level/presence? Preferably something that doesn't require a chemistry degree or a Homeland Security background check before I can get the necessary reagents. But any ideas at all would be much appreciated.

I've got a bunch of other thiosulfate related questions, but I'll save'em for now. For the sake of conversation beyond my ignorant bleating, I'm posting the link to a thiosulfate patent application I've been studying:

http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PG01&s1=20100111751.PGNR.&OS=DN/20100111751&RS=DN/20100111751

There's a lot of interesting stuff in there, including the use of sulfides to precipitate values. As I understand it, this opens the door to regenerating the leach with relative ease and economy.

I'm hoping to get some good thiosulfate discussion going in this thread. The chemistry is complex and confusing, but on the other hand it's a fairly selective leach, and the low toxicity and minimal fumes make it a pleasure to deal with. So anyone else with questions or comments about this leach process should feel free to post in this thread. All I ask is please keep the posts related to thiosulfate, thanks.

Devon


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## Juan Manuel Arcos Frank

Devon:

Welcome to the Forum.
We have talked a lot about Thiosulphate process...take a look writting the process in the search box.

Thio process is more expensive than cyanide process..this is why it is not used in mines but it could work with our e gold scrap recovery.

Have a nice day.

Manuel


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## dev

Hi Manuel, thanks for the response. I have done a lot of searching of the forum on the topic of thiosulfate, and read every thread that shows up in a search - most of them several times. The topic has come up numerous times, but there really isn't much hard information -nothing like the body of info available on the HCl/Clorox leach, which comes complete with a long list of problems, resolutions, and pretty pictures.

This article seems to be the source of most of the thiosulfate information that's floating around, it's the Yen, et al pdf:

http://www.scribd.com/doc/16798725/Thiosulfate-Leaching-as-an-Alternative-to-Cyanidation

There's a cost estimate chart on page 16 of that article, comparing cyanide and thiosulfate, and putting the thiosulfate costs at $9.66 per ton - roughly double the cost of cyanide. However, that figure doesn't take into account the possibility of regenerating the leach. Which appears to be possible for thiosulfate and would drop the cost per ton significantly. Of course this is all industrial scale. I can't process a ton of anything for $9.66.

I'm using the typically recommended concentration of 0.3M for the thiosulfate. My understanding of molar concentration is weak at best, but here's how I get 0.3M: I use the molar mass of Sodium Thiosulfate Pentahydrate, 248.21 g/liter, and multiply by 0.3 for a result of 74.46. That's the number of grams of thiosulfate I add to 1 liter of water.

I paid a walloping 9 dollars for 500 grams of Sodium Thiosulfate from the ChemistryStore.com, and if my concentration math is anywhere near correct, I can make 6.7 liters of leach with that quantity.

I can flood 10 pounds of damp, <30 mesh ore with 1 liter, so my 9 bucks worth of thiosulfate will process at least 66 pounds of ore. Just one gram of gold from all that ore would pay for the chem and leave a wide profit margin. And if it took that much ore to get a gram, I'd be looking for better ore. In other words, even if you pay a lot for thiosulfate, as I did, it's not expensive at all. The industrial notion of 'expensive' has seeped into the community of the 'little guys', and I suspect it's preventing people from trying a viable option for small scale extraction, both from ore and e-scrap.

Cheers,
Devon


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## Anonymous

Use ammonium hydroxide to adjust PH, also, add a few grams of copper sulfate to help as a catalyst.

you also need air pumped into the system, stirring.


Jim


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## dev

Thanks James, that is indeed what I've been doing, using small amounts to lift the pH back up to 9.8 when needed. I haven't added copper because there is already a lot in the ore, probably more than I'd like, actually. I'm still going to try adding copper in later batches, when I know what to expect and can determine the effect the added copper has. As for aeration, I've got the bubbles on constantly, with half a dozen good stirs daily.

Even if I didn't have a pH issue, I'd still be interested in a way to assess thiosulfate levels in a batch. It would help figure out when to add thiosulfate, when too much has been added, when to stop leaching and start dropping. I'm still hunting 'round the net but so far no joy. When I know more chemistry it will probably seem like a simple thing to do, but I'm not there yet.

Cheers,
Devon


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## Anonymous

I would try the HCL/chlorox leach first, but use a sealed container, cut way down on the HCL, and use enough chlorox to convert nearly all of the HCL to chorine gas. 
DO not use a glass container, use a 5gl bucket with lid.

I use this for IC chips. I put the ground chips in to about 1/3 of the bucket deep, then I use HCL which the amount depends on the expected metal content, to much does not hurt but is wastefull, I put this in a plastic drink cup (disposable) and force it down into the ground material (so it does not spill) I then add the chlorox which is also in a plastic cup and force down so it will not spill.

I drill a 1/2 inch hole in the lid (relief valve, kinda thing) that I have a rubber stopper to fit. snap the lid on tight. Now here is the tricky part, tip the bucket so the HCL and chlorox mix, then set the bucket back level and test for chlorine gas coming out of the hole with a q-tip that has been dipped in ammonia, white fumes will tell that the bucket is full of chlorine, once this happens cork the hole and roll the bucket around to mix the chlorine gas with the "ore" leave this set for at least 24 hours, rolling again to mix about every six hours or so.

When this is done you can extract the gold by rinsing with water and draining, I reuse the water several times to get a high enough concentration to drop the gold from.
You can then extract your silver chloride with the thiosulfate, I do not bother because of the low value of silver and low content in my IC powder. If your ore has higher then it may be worth it.

The HCL is what reacts with the iron oxides, by eliminating the excess HCL and using chlorine gas, hardly any of the iron compounds are reacted with.

I think if you get the process above down, then you will not really want to use the thio, as you skip many steps involved in the thio process.

This is my adaptation of the Plattners Process that has been used for 100 or so years.

Jim


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## Platdigger

Since thyosulfate will kill or neutrolize chlorine, I would imagine it is a titratioin done with measured amounts of chlorine to a measured amout 
of leach.
Just a guess of course.
After writing this, I found this:

Standardizing a Sodium Thiosulfate Solution
This method presumes that you know the concentration of the thiosulfate solution. In the first week of this experiment, you will prepare a roughly 0.02 M solution of sodium thiosulfate and determine its concentration accurately (standardize it). You will keep this solution until the second week, and then use it to titrate bleach and unknown samples.

For determining the exact concentration of thiosulfate, you could carry out the process described by equations 1 and 2, starting with an accurately weighed sample of solid sodium hypochlorite. But sodium hypochlorite itself is a poor choice for this purpose, because the solid compound absorbs water, and so a weighed sample contains an unknown mass of the salt, and hence an unknown number of moles of hypochlorite ion. A better choice of oxidizer is potassium iodate, KIO3, which can be purchased in high-purity, anhydrous (water-free) form. A solution of known molarity of IO3- ion can be prepared by dissolving a carefully weighed KIO3 sample in water and diluting accurately to a final volume. In this experiment, an accurately prepared solution of KIO3 is provided, with a concentration of 5.00 x 10-3 M. 

The standardization procedure is the same as for the titration: allow a specified volume of this oxidizer to convert iodide ion to iodine, and then use the thiosulfate solution to titrate the iodine produced. The net ionic equations of the standardization are as follows:

IO3- (aq) + 5 I- (aq) + 6 H+ (aq) ---> 3 I2 (aq) + 3 H2O (l) (Eq. 3) 
and 

2 S2032- (aq) + I2 (aq) ---> 2 I- (aq) + S4062- (aq) (Eq. 2)

After titrating the iodine produced by a precisely known quantity of KIO3, you can find the number of moles of thiosulfate in the volume of thiosulfate delivered, using stoichiometric conversion factors from equations 3 and 2, as follows:

# mol S2032- = (2mol S2032-/mol I2 )•(3 mol I2/mol IO3-)•(mol IO3- titrated)
Intensifying the End Point
As the titration proceeds, the iodine color fades from light brown to pale yellow. It is difficult to see the last traces of iodine color. To make the endpoint easier to detect, once you are near the endpoint, you will add a small amount of starch solution to the titration flask. Starch reacts with a mixture of iodine and iodide ion to form a noncovalent complex of starch and I3- ion. This complex is very dark blue, much more intensely colored than the equivalent amount of iodine. At the endpoint of the titration, the solution turns suddenly from intense blue to colorless, making it easy for you to see when the last traces of iodine have been titrated.

So, what you would need to do this is potasium iodate .
Here is were I found this: http://usm.maine.edu/chy/manuals/116/text/RdxTi.html


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## Anonymous

I should add use ferrous sulfate to drop the gold from the plattners process bucket heap leach method.

Jim


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## dev

Platdigger, thanks a million for that. I saw those instructions a couple weeks ago but dismissed them because I couldn't see where the iodide was coming from, and generally didn't understand the process very well. After reading the whole thing more carefully, and enough times for the info to sink in, I think I get it. And it seems like my best test option at this point.

So here is my take on the first portion of those instructions, tailored to my situation and hopefully broken into simpler steps for people as chemistry-challenged as I am. I could go very wrong very easily here so if someone sees an error please holler and I'll make corrections.

There are two titrations necessary, the first one uses a known volume of Potassium Iodate (KIO3) to convert a colorless Iodide (I-) solution to an Iodine (I2) solution with its familiar color.

The second titration uses Sodium Thiosulfate solution(in my case a sample from an ongoing leach) which is added gradually to the colored Iodine solution until the color vanishes. When this endpoint is reached, the amount of thiosulfate that was needed is then used to calculate the thiosulfate concentration.

Before any of this can happen, I need an Iodide solution. This is where I got stuck the first time I saw this process. I now think that I can simply put a quantity of Iodine in deionized (DI) water and then reduce the Iodine to Iodide with the addition of Sodium Hydroxide (Lye). Won't need much Iodine, just enough to produce an obviously colored solution. I know elemental Iodine isn't soluble in water, but if I understand correctly it will dissolve when converted to Iodide.

Danger, online scam shop!! -->Buying Iodine here: http://www.sciencelab.com/page/S/PVAR/SLI1513?gclid=CPqm5vqRh6QCFUWC5QodVkKYLA

$52.02 for 25 grams of Iodine crystals. And they say Iodine doesn't sting... 

Also need Potassium Iodate solution. Instructions call for a concentration of 5.00 x10-3M, also known as 0.005M. I've decided to get my KIO3 here, 100 grams of a cheap grade for $11.75, should last me a good long while:

http://purebulk.com/potassium-iodate

Molar mass of KIO3 is 214.001 g/mol. Multiplied by the target concentration of 0.005M = 1.07 g. So I'll add 1.07 grams of spanky new KIO3 powder to 1 liter of DI water.

Going to need a new toy to do these tests - a graduated buret for doing the titration. Since I'm already ordering chem from Sciencelab.com, I'll get one from there, the 25 ml capacity version:

Danger, online scam shop!! -->http://www.sciencelab.com/page/S/PVAR/10-208-3

I'll homebrew a buret stand. So, all supplies are ordered, with a bit of luck I might be test driving that new buret on the weekend. I'll post progress in this thread.

Edit note, Oct. 6, 2010: After waiting a long time and getting no response to emails or phone calls, I finally searched ScienceLab.com and discovered I'm far from the first person ripped off by this 'company'. I just hope nobody followed the links and bought from these crooks.

-------------------------------------------
James:

Ore no touchy the HCl? Well that just seems way too simple and straightforward and sensible. :mrgreen: Seems like the catch there is getting the chlorine gas to penetrate the ore, but I suppose a bit of positive pressure like you have in your setup would do the trick. I'd also need to make sure the ore was as dry as possible to avoid generating new acid within the heap.

I think rather than the disposable cups you mentioned, I'd be inclined to nest two buckets to ensure complete separation of acid and ore. Perforate the sides of the interior bucket above the ore line (assuming there's an airspace between the sides of inner and outer bucket). Use the gap between bucket bottoms for the HCl and Clorox. Need to seal the contact area between the buckets, and still need a lid with relief valve for the top bucket. Cadillac version would be stirrable without taking the lid off.

I might have more silver than I'm willing to lose, but as you said, an additional step would take care of that.

Looks like when I get the thiosulfate figured out I'll have to do an ore cook-off. Matching quantities, two processes, same leach time, see which one has maximum advantage. Sounds like fun, wish I'd gotten into this stuff years ago. Thanks for your suggestion, I'll give it a go.

Cheers,
Devon


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## Anonymous

The ore can be damp. Chlorine is heavier than air, there is no problem mixing, and no need to make sure that not one drop of hcl touches the ore, it will be used up and does not hurt if you are not soaking the ore in hcl.

when you dump the bucket on its side to spill the hcl and chlorox together they react instantly releasing large volumes of chlorine which will displace the oxygen from the container.

Jim


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## qst42know

Does the oxygen in potassium iodate KIO3 interfere with what you are trying to accomplish?

I would guess you are still paying for the iodine content diluted with potassium and oxygen. 

Are you certain this is a bargain?

Pound for pound potassium iodide KI would contain more iodine correct?


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## Platdigger

Devon, sounds like you have a better grasp of this than I.
You may have seen this over silpification also:

"Add an accurately weighed amount of iodine to a solution of excess
potassium iodide. Stir until the iodine is completely dissolved. The
solution is highly colored due to the formation of the monovalent anion (I)3. Titrate the tri-iodide solution until it is colorless."

qst42know, about this iodine thing. We are only trying to use it as a method to determine how much available thio is left 
in a leach at a given time.
The iodine is not involved in the leach it's self.


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## dev

A slight hitch in the testing plan. Got an email from sciencelab.com telling me that stuff in my order (no items specified) is backordered and could potentially take 2-3 weeks to get to me. :roll: Next time I need supplies I'll be looking for somewhere that actually stocks the things they supposedly sell.

They also requested a letter of intent and a copy of my driver's license. Hmmm, my intent for the buret, or the iodine, I wonder? Or maybe it was the beakers... Naturally I was compelled by this clever regulation to confess in my letter of intent that I plan nothing short of social mayhem and World Domination through the diabolical use of 25 grams of Iodine. Curses, foiled again! Now I have to scale back my Master Plan to just tinkering with thiosulfate on the back porch. Hopefully that will still be a legal activity by the time my stuff arrives.


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## jimdoc

You can make your own iodine if they won't sell you any.

http://www.youtube.com/watch?v=CLhwkFKLdPA

Jim


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## dev

Thank you Jimdoc, I was thinkin' about doing that. Haven't been shut down yet on my iodine purchase, so we'll see how that goes. But the Potassium Iodide (KI) option got me thinking that it might be preferable for economic reasons as well. Here's my attempt to compare the cost of pure crystal Iodine vs the cost of extracting from KI.

As noted earlier in the thread, I paid $52.02 for 25 grams of crystalline, elemental Iodine.

Looking here:
http://shop.chemicalstore.com/navigation/detail.asp?id=PI1239

I can get 100 grams of KI for $22.00, But how much Iodine is that really? Molar mass of KI is 166.0028 g/mol. Atomic weight of potassium is 39.0983 g/mol. Subtract the weight of the potassium from the weight of the KI molecule, 166.0028 - 39.0983 = 126.90. Looking for confirmation, I check the molar mass of Iodine, and there it is, 126.90 g/mol. So far so good. 100 grams of KI, for 22 bucks, can theoretically supply about 76 grams of Iodine.

Granted, it takes a bit of HCl and oxidizer such as Hydrogen Peroxide or Bleach (Sodium Hypochlorite) to get the goods out of the KI. Based on the video Jimdoc pointed out, it isn't much.

But the price difference between purchased and extracted Iodine is huge. Purchased pure, about (48 cents per gram.) <--corrected to $2.08/gram by qst42know. Extracted, 0.2 cents per gram. That's not a typo, it's a fraction of a cent per gram.

Anyone care to confirm/correct this? That's a pretty wild price gap, makes me wonder if I did this right.


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## jimdoc

Here are some better prices for Potassium Iodide on Ebay (in larger amounts);

http://cgi.ebay.com/Potassium-Iodide-ACS-Grade-500-Grams-/150482555031?pt=LH_DefaultDomain_0&hash=item2309759097

http://cgi.ebay.com/Potassium-Iodide-ACS-Grade-1-Kg-1000-Grams-/150486339091?pt=LH_DefaultDomain_0&hash=item2309af4e13

Jim


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## qst42know

$22.00/76g = .289 cents/gram

$52.02/25g = $2.08/gram

Much bigger difference than you thought.


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## dev

Erm, that's not the part I was expecting to get wrong. Thanks for pointing that out. Meanwhile I've learned from sciencelab.com that there was no 'back order'. When I sent the documents they asked for I also requested they tell me which items were on back order. Was informed that the entire order would ship as soon as their regulatory dept. was done checking me out. Potassium Iodide on Ebay is looking better all the time.

Can Iodine crystals really be 1000 times more expensive than Iodine extracted from KI? I'll check those numbers out again tomorrow, cuz that doesn't seem entirely sane.


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## qst42know

It's likely the paper work required for tracking and reporting iodine sales that add to the cost. The seller may even end up in court if you turn out to be a meth chef.


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## Anonymous

qst42know said:


> It's likely the paper work required for tracking and reporting iodine sales that add to the cost. The seller may even end up in court if you turn out to be a meth chef.



or if you burn your skin off, eyes out, or poison yourself.

Jim


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## Juan Manuel Arcos Frank

Devon:

Where do you live?.

Regards.

Manuel


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## dev

Hi Manuel, I live near Gettysburg in south central Pennsylvania.


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## Anonymous

Thank you so much for posting such a nice article.I considered myself a relatively well informed person but I learned a lot, 
and especially benefited from the overall perspective that i gained from your wonderful article. 
I cannot appreciate you enough for giving me the amazing opportunity to learn so much from your suggestion.
Thank you so much for this info.


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## dev

I detect the distinct odor of ... spam. (It has been removed. Harold)
Update - Now have my Potassium Iodide and Iodate, but have not yet been deemed worthy of Iodine, which is delaying arrival of the buret I ordered along with it. Sooner or later, I'll be posting my attempts to test for thiosulfate. Probably later than sooner.

Cheers


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## Juan Manuel Arcos Frank

Hi Devon.

GREAT HEAVENS!!!!!!!....Why do you live so far from me?.If you would live closer to me with pleasure I would give you 200 lt of ammonium thiosulfate just to develope the thio process for e gold scrap.

Anyway,if you have the will to develope this process I have the will to help you,but of course,there is a price to pay,the price is:share your research with us here in this Forum.

Here are some actions I may guide you:

-A process for making your own thiosulphate.
-The way to get thiosulphate for free
-The process for using thiosulphate to recover gold from golden plated items.
-The process to regenerate thiosulphate.

All you need is some e golden plated items,like pins,fingers or golden plated circuits.

What do you say?Do we have a deal?

Kindest Regards.

Manuel


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## Shecker

If you are dealing with of iron a citric acid pre-treatment would be warranted. Citric acid readily dissolves iron. My experience is that in some ores it will also leach silver. This is simple to test. Add some clean iron to the citric acid. If anything precipitates on the iron then treat it with nitric acid and check for silver.

Thiosulfate leaches will precipitate their values on iron, so you are probably losing at least some of the silver while in the leaching cycle.
Copper readily kills thiosulfate solutions, so it is not indicated in the presence of iron/copper ores. 

One other thing is that both the gold/silver ions are colorless in a thiosulfate solution even at high concentrates. If you get a yellow or gray color it is most likely not gold or silver, unless the concentrate is extremely high.

Electrolysis at 2.5 volts D.C. is a good way to recover values from a thiosulfate solution.

Hope this helps.

Randy


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## Traveller11

Hello Shecker
I have seen citric acid suggested many times on this site for dissolving placer iron into solution.
I was checking it out on the Internet and discovered that it comes in many percentages. It can even be purchased in powdered form.
What percentage is recommended for pre-leaching purposes and can this be prepared from its powdered form?
Regards
Bob


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## dev

Hi Shecker, thanks for the info. I have tried the pre-leach acid wash route and unfortunately it isn't a viable option for me (worth trying to find out, though). I used HCl, full strength hardware store muriatic, which of course attacks iron readily. The solution was very orange in minutes, and two days later was still darkening, heading from deep orange to red. I rinsed with water and washed the same batch a second time with full strength HCl. Same color, two days later. Bottom line, way too much chem used at that point and the iron was still coming. So it was time for exploration of other leaches such as thiosulfate.

I am of course alarmed to hear that values can precipitate on the iron present in a thiosulfate leach. None of the patents or articles I've read so far have mentioned this issue, except in the context of dropping values from a pregnant leach. Could you possibly point me to a source to find out about this problem? Just guessing, I think this would not be a problem as long as the leach remains alkaline.

I'm sure your comment on solution color will be useful to a lot of folks, it's one of those things that hasn't come up much (if at all) in other discussions of this leach. For me, color indications would be out the window anyway, thanks to the dyed dollar store ammonia I've been using. That dye is tough stuff, virtually inert as far as I can tell. I've taken test batches up and down the pH scale while trying to drop values, and when all is said and done the dye is still there.

Electrolysis is definitely on the table as a recovery option. Getting the values out of solution has so far been a trial and error situation. Tough to crack that complex. And even the best drops so far have produced a precipitate so fine it takes days to settle out. After sorting out the testing of thiosulfate levels, recovery processes are the next big hurdle.

-------------------------------------------
Manuel, I can only take you up on part of that deal. The E-scrap bug hasn't bitten yet, so that's a no-go. It's much easier for me to get a pound of interesting rocks and dirt than a pound of CPUs. Not to mention that the best part of this whole thing is having a good reason to stomp around the woods. But I expect scrap will be a lot more tempting when the snow flies, so I reserve the right to future e-scrap addiction.

The one part of that deal I'm good for is sharing whatever I learn about thiosulfate - or any other process. I type fast, so long posts come easy and I'm happy to throw in every detail I can think of that might be of use to someone down the road.

In the patent link I put in the original post there are clues to some of the things you mention, such as regeneration of thiosulfate. I've produced it with elemental sulfur and sodium metabisulfite (SMB). Couldn't tell you how much I made, though, because I still can't test for the stuff yet. :evil: But if you've got a way to get thiosulfate for free, I'm all ears.

Meanwhile, my iodine finally arrived today, but no burette! Maybe next week...


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## dev

Update, sorry this post is off-topic for the thread but I want to make members aware of my unfortunate experience with ScienceLab.com. This is where I ordered my Iodine, burette, and various other bits and bobs - beakers and pH calibration sachets, etc.

Turns out ScienceLab.com is a scam. I did receive a couple beakers and the Iodine, but nothing else. Alarm bells started ringing when I began sending queries last week and got no response. Finally picked up the phone and could not get through to any of the numbers from their website contact page. That prompted a quick google, and suddenly my wallet got that sinking feeling...

Well, it ain't over yet, I'll get what they owe me one way or another. But please, folks, don't do business with ScienceLab.com it's a rip-off operation.


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## lazersteve

I've purchased many supplies from them over the past five years without any problems.

There is a SEO (Search Engine Optimization) virus going around that spoofs your Google results and redirects you to false web sites made to look like the real web site to steal your personal information, perhaps this is what happened to you? If this is not the case then I'm at a loss for words as I've never had any problems with ScienceLab.com.

Steve


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## Shecker

My source on iron being used as a precipitator for thiosulfate solutions is Kodak. They have written extensively on the subject for recovery of fixer solutions (thiosulfate) and the silver they contain. A lot of such data is available on the internet. 

In terms of ores thiosulfates will leach oxides, chlorides, clor-oxides, bromides, iodides, and things of that like. The best method of recovery that I used for a long time on thiosulfate solutions was adjusting the pH to 8 (don't go over) and precipitating the values as sulfide complexes. This is easily done with sodium sulfide. However, be warned, using this with an acid solution will generate copious amounts of H2S, which is never welcome at anybodies party and can be deadly.

One you have the material as a sulfide you can roast off the sulfur and smelt the resulting material. Or it can be smelted as a sulfide -- just make sure you put enough nails in the flux to take up any of the sulfur.

Hopes this helps.

Randy


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## dev

Shecker/Randy, thanks that does help. I'm trying to wrap my head around the chemistry of premature precipitation on iron or other base metals - gonna take a while. I haven't attempted to drop using a sulfide but I do intend to try it. I appreciate the heads-up on the production of H2S (Hydrogen Sulfide) when acidifying a sulfur bearing solution. I was aware of the hazard and I'm glad you pointed it out here. The potential to generate H2S and the risks of using ammonia (especially with feed material that may contain silver) are the two main hazards I bear in mind when working with thiosulfate.

I grew up in the sour gas fields of Alberta, worked a bit in the gas industry. There's a safety video that gets shown to crews at the plants, a rat in a sealed cage about 18" x 12" is exposed to a single drop of H2S in solution. Convulsions commence in seconds, death occurs in less than a minute. I remember two fatalities that occurred near my hometown, the first was a man exposed to a leak, the second was the guy who tried to rescue him without an air pack. H2S is indeed very dangerous stuff.

You mentioned that you have used sodium sulfide for recovery from thiosulfate, did you generate it yourself or just purchase it? I've been wondering if I could produce it using SMB or perhaps magnesium sulfate (Epsom salt) as a sulfur source. Again, more chemistry I need to understand before I can try it, but I'll get there.

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Steve, I'm glad to hear you've had no issues with sciencelab.com. But based on my own experience and the volume of complaints I've seen on the web, I am going to stand by my warning to others. There are two problems that seem to occur most often, the first is that people get used equipment when they expected new, and the other is that orders are partially filled and then never completed. Here is a page put up by one of their disgruntled customers, this story matches my own, except for the resolution:
http://www.ecstaticlyrics.com/bullshit/sciencelab.com/

A search with the company name and 'scam' or 'fraud' reveals a level of customer dissatisfaction that is clearly beyond the norm. I suspect British Petroleum is a more popular company. I always give the benefit of the doubt in these situations, honest errors do happen and even sloppy order handling is not something to get too worked up over. That's why I was willing to wait patiently for two weeks before attempting to contact them - just a polite query about the status of my order. I sent 5 nice emails over the course of ten days, and not one received a reply. Well, maybe they just get a lot of email and I was getting overlooked somehow... So I tried to phone them, and none of their numbers would ring through. I wasn't on hold, wasn't forwarded, no elevator music or phone menus, just a dead line every time. So here's a company that has my money, hasn't sent all my stuff (three weeks waiting for basic lab stuff at this point), and there's no way to contact them to find out what's going on. Benefit of the doubt no longer applies.

I spammed every one of their email addresses with the same angry letter. They got it in sales, accounting, everybody. I'm sure they would have ignored this too but I was lucky to have a big stick to swing - they sold me a List 1 substance. I promised that if I didn't get satisfaction immediately that I would be contacting the DEA to confirm that my Iodine purchase was completely above board. Suddenly, the items that were 'backordered' due to manufacturers replenishing inventory, were on the way to me. To be fair, these items were substitutions, so maybe the original items really were on backorder... but I doubt it. They also flat out lied in their response to me, saying that they'd been trying to contact me by email and phone, but the emails were bouncing back. Yet somehow I was able to exchange several emails following my initial order, regarding the regulatory requirements for the Iodine. And I know they have my correct phone number, I checked my account profile.

Anyway, to make a long story less long, and give credit where it's due - the substituted items hit my doorstep this morning via UPS next day air. They ponied up some cash for that shipping bill, no doubt. So I guess all's well that ends well but I won't spend another dime there and I hope nobody else runs into these problems with them. The best part of all this is that finally I am the happy owner of a graduated burrette. Thiosulfate tests coming soon!


----------



## goldsilverpro

It sounds like Steve was very lucky.


----------



## lazersteve

I'm glad your supplies arrived. 

Also thank you for the notice on ScienceLab.com. Perhaps they are going through some kind of management change or were sold recently?

It's been about 6 months ago since I last used them.

Steve


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## Shecker

I have never tried to generate H2S because of the dangers. Sodium Sulfide is fairly inexpensive and available through many chemical supply houses. I haven't used any for years now but I use to use it all the time.

Rather than trying sodium thiosulfate why not try ammonium thiosulfate. It backs a little bit more punch. It is generally used with copper sulfate as an oxidizer. This is one case where an ammonium compound does not generate dangerous compounds -- having said that a little reading on the internet would prove a valuable safety factor.

Randy


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## dev

Funny thing. I had to buy chem and glassware, wait for weeks, squabble with an online store, and begin to headscratch my way through the stoichiometry of two separate titrations in order to finally grasp how simple it can be to monitor thiosulfate levels in a leach. (Not the quickest bunny in the woods, I know.)

How to test thiosulfate levels in a leach:
This method is a greatly simplified version of the process Platdigger found and posted earlier in this thread. This won't provide any hard numbers for concentration, but it will reveal if thiosulfate levels are changing, and in which direction. Also handy for finding out if a used leach has been regenerated successfully.

It all comes down to the fact that when you add thiosulfate to an Iodine solution, the typical Iodine color will vanish as the thiosulfate converts the Iodine to colorless, soluble Iodide.

The key is to use the same Iodine solution, and exactly the same amount of it, for each test. Pharmacy tincture will work, although in the long run it would be many times cheaper to buy some Potassium Iodide. Add a drop or two of HCl to a small sample of whatever Iodine source you choose, then add drops of hydrogen peroxide as needed. Don't take it so far that the Iodine precipitates, just get the solution strongly colored with Iodine. Make it in a sealable container so Iodine levels stay consistent for each test.

Test the thiosulfate leach when it's fresh, before adding it to the feed material. Add the thiosulfate one drop at a time to a precisely measured sample of the prepared Iodine solution. (I've been using a little 10cc syringe to quickly and easily draw a repeatable quantity of Iodine) Count the drops of leach solution needed to make the Iodine solution colorless. That's the baseline measurement of full strength thiosulfate. With that in hand you can start the leach and repeat the test as often as desired. As thiosulfate is consumed in the leach, it will take more drops of it to make the Iodine solution colorless.

So that's the easy version of thiosulfate testing. I'm still working on learning how to determine precise concentration using the process Platdigger posted. Gotta puzzle out this equation from that post:
# mol S2032- = (2mol S2032-/mol I2 )•(3 mol I2/mol IO3-)•(mol IO3- titrated)

I don't know yet where all the values come from in that equation, in particular the 'titrated' bit in the last section. Won't get to it right away because now that I have a viable thiosulfate test it's time to crush some material and leach a batch or three.

Cheers


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## Platdigger

That is great Dev, 
Now I am curious if that when you start adding ammonia to your leach, the test goes right out the window, or no.


----------



## dev

Platdigger, that's exactly what I've been wondering too. Early indications are that it works, but that's judging by only the two tests I've done on the leach I started yesterday - so not much to go on yet. And I've already made a mistake with those tests, using too little Iodine solution. I was trying to get by with only 2 mL of Iodine but such a small quantity makes it difficult to observe changes from one test to the next. The difference between my baseline and the second test 12 hours later is just one drop. Baseline was 5 drops of thiosulfate/ammonia, this morning it took 6 drops. I repeated both tests 3 times to confirm results. I'm stuck with using 2 mL of Iodine solution for this leach, but next time I think I'll use 10 mL.

Back to the ammonia, for anyone considering using this test I want to point out the hazard of combining Iodine solutions with ammonia. Lou brought this up in the 'Situations to Avoid' safety thread here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=3781

*Theoretically* this isn't a problem with the tests I'm doing, because the thiosulfate ensures there is no free Iodine to form explosively unstable Nitrogen Triiodide. But 'safe in theory' doesn't cut it. The way to be sure is to dispose of test solutions immediately after use, and wash containers, droppers, etc. Drips or spills can't be allowed to dry, and it would be a bad idea to save used test solutions for later recovery of the Iodine.


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## Juan Manuel Arcos Frank

Devon:

Ok,download this book:

http://www.archive.org/details/hydrometallurgyo00hofmrich

try to read those chapters about thio leaching process,specially "Russell solution".You can get sodium thiosulphate(ST) from hospitals,X ray gabinets and newspapers and using sodium sulphide process recover silver and regenerate ST.

Boiling lime with sulphur you can make calcium polysulphide and calcium thiosulphate(CT):

3CaO + 12S--------2CaS5 + CaS2O3

now add some sodium sulphate and you will form a precipitate of calcium sulfate and a solution of ST,pour off and you will have all ST you need for your thio gold process.

Try to find out if you can buy ST cheaper,I am posting for you a letter from my chemical supplier store with ST and ammoniun Thiosulphate(AT) prices.It is in spanish and mexican pesos.

Keep us posted about your progress.

Have a nice day.

Kindest regards.

Manuel


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## dev

:shock: 

Manuel, I had to force myself to stop reading that book and take a minute to say thanks. Awesome link, I'm sure I'll be reading the whole thing more than once.

I'm not sure our deal is working out though. I offered up a dusty little pebble of information, and you delivered a treasure chest. :mrgreen: Now I've gotta get back to that book...

Cheers,
Devon


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## Shecker

I thought I would a few things that I have learned the hard way over the years concerning leaching with thiosulfates. When thiosulfate leaches work they work very quickly. The leach cycle is measured in minutes. Think of it this way -- when removing unexposed silver bromide from film you want something that isn't going to take a couple of weeks to carry out its reaction. The measdured disssolution of silver bromide in sodium thiosulfate is measured in minutes -- in that only cyanide is faster. 

In cases of mineral leaching using thiosulfates the dissolution of precious metal compounds is also very quick (although there are times when the opposite is true). There are ways of testing the effective rate of a leaching ( some internet search would prove rewarding). My personal experiene with sodium thiosulfate is that in an average of 15 minutes the solutions would be loaded. Also keep in mind that there is a point where values will begin to precipitate out of any solution. Changes in temperature, pH, solution concentration, sulfite concentration, oxidizer concentration, and even sunlight can effect whether or not atom A goes into solution or sticks its tongue out at you in complete defiance. The point is a few simple tests can go a long way to cut down on those unknown factors that can happen in leaches.

One summer back in the 1970's I got into experimenting with various iodides of precious metals and their solubility in sodium thiosulfate -- just for curiosity. What I found was this:

Heavy black gold iodide dissolves readily into sodium thiosulfate and produces a colorless solution.
Yellow silver iodide dissolves readily into sodium thiosulfate and produces a colorless solution.
Yellow platinum iodide readily dissolves into sodium thiosulfate and produces a yellow solution that looks a lot like iron.
Palladium iodide (which is black also) readily dissolves into sodium thiosulfate and produces a colorless solution.
Rhodium iodide readily dissolves into sodium thiosulfate and produces a lovely rose colored solution.
Ruthenium iodide readily dissolves into sodium thiosulfate and produces a lavender/purple colored solution.

I didn't do any testing on either Iridium or Osmium. The New Mexico Bureau of Mines produced me with the iodide samples in gram amounts. They didn't have either Iridium Iodide or Osmium Iodide. After I discovered a new mineral in New Mexico and let the State Mineralogist name it I was they're fair haired boy.

The best method of recovering the values from a thiosulfate leach that I ever found (and I tried everything in the books) was by sulfiding the solution at a pH of 8. If extra sodium sulfite it available during sulfiding of the solutions it can even lead to the in situ regeneration of sodium thiosulfate.

Anyway I hope this helps.

Randy in Gunnison


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## Remuck

Greetings and many thanks to Dev, Jaun Manuel, James122964, Platdigger, jimdoc, qst42know, Shecker,Traveller11, and lazersteve for their contributions to this thread, it (the thread) being several months old, I can only hope that some of you will be able to view my question. I have a rare opportunity to participate in the processing of gold from old tailings out here in the "Mother Lode" of CA. and although, ultimately, I will primarilly be involved with assaying samples for the sake of getting the processing equipment "dialed in", I'll also be doing so for the sake of keeping the out of state processers honest. The ore that we'll be dealing with has been assayed at 2.5 to 3.8 oz's/ton, unfortunately the individual with whom I'm working has no documentation to back those figures up --- they are "anecdotal" from an the Oldtimer who is allowing access to the material. My question concerns an attempt on my part to leach some values out of the material that my frustrated partner has been working for over six months without anything to show for it, sans the odd rock that does contain discernable free gold. I've used a commercial preparation (9.15 lbs total weight) consisting of approx. 27% Ammonium Sulfate, 73% Sodium Thiosulfate, and what appears to be approx. 3+ grams of Copper Sulfate (ostensibley as a buffer). Four oz's of this mixture is disolved per gallon of water to make the leach (lixiviant) and is mixed with ore at 5-10 parts to 1 part ore ( ground to 200+ mesh) at 120 degrees F. and an ideal ph of 9.2 (attained by adding ammonia). After 1.0 hour all is allowed to settle, pregnant leach is poured off and another "proprietory" reagent is then added until a precipitate is formed (a VERY fast end point). Out of 400 gms of 700 mesh material I netted approx. 1.5 grams of a precipitate that was dark brownish and sludgy when wet and looks like brown mustard when dry. We were all fairly excited about the results until today when, as a control, I added some of the "proprietory reagent" to some leach WITHOUT any ore and clearly noted a precip. albeit lighter in color. Am I on the right track here? I took three years worth of chem. 30+ yrs. ago and the stiochiomentry is a bit vague, as is the mystery reagent that has a sulfuric odor to it. I've been successful in reducing the shipping weight of the concentrates by 35% by removing iron (as magnetite) and burning off sulfides; however the ore that I leached was not so processed. Any and all input would be greatly appreciated!! I plan to either fire assay or utilize aqua regia to further process the "values" (?) that I recovered, but would appreciate some opinions before purchasing any nitric. CA. is truly a VERY difficult state to work in and I'm loathe to get on some sort of "watch list" prematurely --- meth. heads have truly screwed things up for the rest of us. Looking forward to a response and scratching my head a bit, Lance in CA.


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## qst42know

> The ore that we'll be dealing with has been assayed at 2.5 to 3.8 oz's/ton, unfortunately the individual with whom I'm working has no documentation to back those figures up --- they are "anecdotal" from an the Oldtimer who is allowing access to the material.



I would guess a real assay from a trusted firm would be prudent. Acids on ores may only leave you with more questions and no answers.


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## Remuck

qst42know,

Thank you for your response. I agree, another few assays would be the correct way to go; however, what I did not mention in my last (first) post is the fact that my friend has, over the past five or so months, affiliated himself with at least two other people who, on his dime, have had the tailings assayed at a cost of from $200 to $250 two times that he is sure of and they have not only NOT provided any documentation, but have disappeared with several tons of material. That is the reason why I purchased the thio-sulfate leach --- to encourage him and get that "glimmer" back in his eyes. I know that I can perform a fire assay and am not intimidated by the chemistry behind colorimetric assaying, but before investing in the materials to do so, I thought that it might be a moral booster to spend less than $60 to actually SHOW that the project is worthwhile by purchasing a commercially manufactured leach and giving him something to hold in his hand. My friend has owned a logging company for the majority of his life and, having little or no experience with mining, has been taken advantage of in a big way. I just wanted to show him something tangible that would take a little of the stress out and thought that I had done so, BUT am now questioning the results of the thiosulfate leaching AND the "mystery reagent" (perhaps some sort of flocculent). It just didn't occur to me to double check the procedures before revealing the results. 

I have cupels and, with the purchase of a bit of PbO and borax, I can conjur up an appropriate flux and perform a quick fire assay, but, having found this forum, I thought that I might toss the question of the "thio-leach" out to get some opinions. The instructions for the proper use of the product were fairly straightforward, but, in the back of my mind, I can't help but think that I may have missed something. If you or anyone you know is intimately familiar with thiosulfate leaching, I'd greatly appreciate some feedback. I'd hate to throw yet another disappointment my friends way at this point. I really don't know the "ins and outs" of this particular forum, but if it's possible for you to get the word out, I'd greatly appreciate it.

Thanks again for your response, Lance


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## nickvc

Lance welcome to the forum and even though I can't help you I would suggest you get in touch with our resident expert on minerals and ores Richard...the rock man who can probably be of help and can definitely provide you with an assay and also trade the ores with his contacts if that's the way you decide to go.


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## Remuck

nickvc,

Thank you for your greeting as well as the info. It sounds as though "Richard ... the rock man" would, indeed, be the man to perform an up to date assay with, of all things, numbers and such on a piece of paper that could actually be filed away for future reference! Direction and accountability have been the missing factors in this endeavor from day one, which is why I have stepped in. Aside from the tons of ore that were high-graded by previous "partners", my friend has forty or fifty 5 gal. buckets of concentrates spread around a three state area. In short, his "ah shucks" approach to this project has not panned out and, with countless tons of material to be worked, it's high time to get organized.

As I previously mentioned, the only reason that I purchased the commercially prepared thio-leach was to finally provide my friend with values that he could hold in his hand. Taking CA. regulations into consideration as well, I thought that the relatively benign nature of thio-leaching would be less likely to raise the hackles of regulators. The process being relatively straight forward, I didn't think that there was much room for error, thus it didn't even occur to me to run a control in parallel with an ore run. To put a positive spin on things the mystery precip that I noted in my control run could very well be an expected chem. reaction that, had ore with values been present, would have dragged the values out of solution as well. That would explain the lighter color of the control precip compared to the material runs.

Keeping my fingers crossed.
Regards, Lance


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## qst42know

As I understand it the efficient leaching of ores varies greatly by the nature of the ore itself. An assay from a lab that only does assays might reveal the correct process or processes required for your ore as well as the potential value. 

It's a good sign the outfit you sent material to wants it, but a very bad sign they haven't provided the assay result you paid for.


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## Ferrell

We want to use sodium thiosulfate as a leach for ore crushed down to 150 mesh that contains (tested) microscopic gold, a little free gold that's too small to pick out with your fingers, and silver. We have sodium thiosulfate in crystal form from a chemical company, but don't know the water to chemical ratio for putting it into solution. Once it goes through the leaching process we're fine, as we've used other leaches, but want to get away from toxic chemicals to something safer and more bio degradable for the first phase. Can someone tell us what the mix ratio for water is? We know it works best if kept between 60 and 80 degrees F., and it only needs aprox 30 min to an hr to work (although we've read at least one article that stated up to four hrs), and we've heard as little as 15 minutes. We'd love some accurate info, and does it work independent of any other chemicals being added for the leaching phase? Thanks for any help you can provide.


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## nickvc

Ferrell said:


> We want to use sodium thiosulfate as a leach for ore crushed down to 150 mesh that contains (tested) microscopic gold, a little free gold that's too small to pick out with your fingers, and silver. We have sodium thiosulfate in crystal form from a chemical company, but don't know the water to chemical ratio for putting it into solution. Once it goes through the leaching process we're fine, as we've used other leaches, but want to get away from toxic chemicals to something safer and more bio degradable for the first phase. Can someone tell us what the mix ratio for water is? We know it works best if kept between 60 and 80 degrees F., and it only needs aprox 30 min to an hr to work (although we've read at least one article that stated up to four hrs), and we've heard as little as 15 minutes. We'd love some accurate info, and does it work independent of any other chemicals being added for the leaching phase? Thanks for any help you can provide.




I'm far from an expert on minerals or ores but I would first find out the exact values you are trying to extract, an assay will give you this information, without it how do you know whether you have extracted all the values in your material? I know it's a large cost upfront but it could save you fortunes in either wasted chemicals or lost values. If I was in your position and were sure I had values I'd want to know exactly how much I was looking to recover and how much was been left 
behind and whether it was worth the cost and effort.


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## Ferrell

Thank you for your input, we appreciate it. We've had several assays as well as lab tests and an actual gold extraction, and know we have very high values in gold and silver, well worth the effort and chemical cost. We just need to know for sure if straight thiosulfate/water solution (and what ratio) is adequate for a basic leach for gold and silver, or if any other compounds need to be mixed with it.


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## Platdigger

Have you read any of the patents?
For gold, unless it is already in your ore and available you will need a catalyst such as some form of copper, perhaps sulphate, or perhaps even iron.
You will also need some ammonia.


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## Ferrell

Thank you. Do you know how much water you mix with the thiosulfate crystals? What the water to chemical ratio is? You say 'some copper sulfate' or 'some ammonia'....what is 'some'? The ore has heavy deposits of iron in it, we did find that out when it was tested.


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## sawmill

Ferrell

Here is the recipe for your mix.
Two ounces of sodium thiosulfate per gallon of water.
Add ammonium sulfate to the mixture until the ph is 9.2.

Also you may want to do a couple small test runs. Do one
without the ammonium sulfate,and one with. Some ores do
not need the Ammonium sulfate or any copper bearing additive.

Keep air bubbling in your leach tank,while leaching. Drop your
gold with sodium sulfide,or SMB. The sodium sulfide is better.


----------



## Ferrell

Sawmill, thank you SO much, this is exactly what we needed! We've been using butyl diglyme then oxalic acid to drop the gold and have that on hand already, and it's worked well, but we'll keep the sodium sulfide in mind, and if we can find some locally might try a test run to see how it compares. Not familiar with what SMB is?


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## sawmill

Ferrell
The sodium sulfide will regenerate your leach water,so it can be
reused. Also it will not drop the copper and other junk with your
gold.
There is lots of ways to precipitate the gold,but some will drop
everything. Some will create a hell of a mess for farther refining
too. No two ores are the same,so you may have to play with it,
until you get it right.

P.S watch your run time. If things are right the leach works fast.
If left too long,and the PH drops,it will also drop gold. Keep your
PH at 9 to 9.2 while leaching.


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## Ferrell

The butyl will drop gold, silver and platinum, from what we were told by one person who has a small lab and does a lot of this type of work, and it doesn't drop the junk metals. I'll have to look into the sulfide, I like the idea of the leach being reuseable. Just the one time, or more? How would you know when it's no longer working? Any signs to watch for, or a certain number of uses?


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## sawmill

Ferrell
No you can reuse the leach over and over,by recharging with sodium
sulfide. You may have to add a little ammonia,or ammonium sulfate
to bring the PH to 9.2. Some use HCL and lye to adjust the PH. I try
to avoid that like the plague. A good fire assay will tell if there is any
gold left in the sediments or leached ore. Also if you know how much
your ore assayed per ton ,then you would have a good idea about your
recovery rate ,from the leaching process.

Most ore only takes a few minutes to leach. Some can take up to four
hours. Once your leach is saturated ,it will start dropping gold. Watch
the PH,if it starts dropping below 9 ,your leach is getting saturated. It
takes some tinkering to figure your run time.

I have learned what little I know by trial and error. There is lots of
conflicting information on thio leaching. Sometimes I think it is
more of a learned skill,than a science. A good PH meter will be your
best friend.

I need to add some more information,that I forgot to post.
For those considering using sodium sulfide,it does have some draw
backs. First it is expensive,and hard to buy,in any great amount,
without the right qualifications.
It does produce toxic gases,and can be explosive,in certain situations.
There really is no such thing as a totally safe or harmless leaching
process.


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## Ferrell

Just another quick question on the sodium sulfide you're using to drop the gold. How are you mixing that? Do you put it solution first (we just checked with a chemical company and can get it in a small container or 55 lb bag....not sure which to get) and if so, what's the ratio of sulfide to water and how many parts do we add to the leach?


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## Ferrell

Shecker said:


> The best method of recovering the values from a thiosulfate leach that I ever found (and I tried everything in the books) was by sulfiding the solution at a pH of 8. If extra sodium sulfite it available during sulfiding of the solutions it can even lead to the in situ regeneration of sodium thiosulfate.
> 
> Anyway I hope this helps.
> 
> Randy in Gunnison




Sawmill said: No you can reuse the leach over and over,by recharging with sodium sulfide.

Now my question, based on these two quotes from two people who both seem very knowledgeable--One of you said sulfite (or sulphite), the other said sulfide, and I now they're both available. In fact, when I placed an order yesterday for sodium sulfide the man taking the order wanted to make sure that's what I meant, not the other one. So now I'm confused, which one do I actually need?

Thank you!


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## Juan Manuel Arcos Frank

No,no,no!!!!!!...Sodium sulfite is Na2SO3,sodium sulphide(or sodium sulfide) is Na2S,they are different salts.Sodium sulfite is a white powder,sodium sulphide is a yellow powder(or flakes,anyway)...sodium sulphide is the right stuff to precipitate silver(or gold) from thiosulfate´s solutions,besides,it regenerates thiosulfate solution to continue using it again and again.

BTW,keep your eyes open when using sodium sulphide,if pH is low(below 6) hydrogen sulphide(H2S) could be formed and released,it smells like rotten eggs and it is very toxic.

Kindest regards.

Manuel


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## sawmill

Ferrell
The sodium sulfide is correct,as Manuel pointed out,and as I told you.
I don't bother with trying to regenerate the leach. It is too complicated
for a small operation,that just does batch leaches.
Regeneration is for a continuous leach operation,on a large scale,not
small operators like myself. Thio is cheap,and a little bit goes a long
way. I just use the sodium sulfide to precipitate the gold because it
works so well,and doesn't drop out all the other junk.

I have used sodium meta bisulfite ,but the sodium sulfide does a
lot better job for me. I just add it dry a little at a time and stir it
in,until the gold starts to drop.Actually you can drop the gold with
HCL acid,but I wouldn't recommend doing it like that.

I am not a chemist ,or too good with all the technical calculations,just
another prospector trying to figure out a leaching plan. Like I said before,
no two ores are the same. You will have to play with your formulas and 
adjust for your specific ore. There is a multitude of ways to recover the
gold from the thio leach. You will have to figure out which one works
for you. 

If Manuel or anyone has a simple way to regenerate the leach in a small
batch,I would sure like to know how.


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## Shecker

Just two things I would like to add about thiosulfate chemistry. 1. When it does what it does it does it really well. 2. When it doesn't do what it is suppose to do, yelling threats and shaking ugly sticks at it won't help. Trust me, I know.

Sorry.

Randy


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## sawmill

Randy
Thio leach is like Grandma's recipe. For some reason it works
every time for her,but it doesn't always work quite right for others.
The bad thing is that there is so much conflicting information,out
there . Seems like everyone and his dog,has a secret formula or patent,
and a lot of the stuff is pure BS.

I have managed to make it work pretty well,but it can be a pain in
the butt to figure out.


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## Juan Manuel Arcos Frank

Sawmill:

Secret fromula?..Here,in this Forum,there are no secrets.

Do you want to know how I regenerate thiosulfate to use it again and again?...let it be:

The process is too simple,just let settle down the black mud(silver or gold),siphon the liquid,filtrate the black mud with silk fabric(I do not know the name in USA,but here in Mexico is called "Molletón",used to make curtains and pillows),collect all the liquid and add some sodium sulfite,it destroys sodium sulphide´s leftovers(because Na2S smells bad) and thio is ready for reuse.

My customers are happy to use this process because they do not have to buy any fixer.Of course,there are people really upset with me,who are they?,well,bad guys,all of them,like Kodak,Fuji,Russell and a long so for because they are not able to squeeze my clients anymore.

Kindest regards.

Manuel


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## sawmill

Manuel
Thank you very much,I appreciate your help.
I will try your suggestion on my next batch in a few minutes.
Greg


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## Ferrell

All of this has been so helpful. We didn't end up getting the sodium sulfide at the place we thought we could get it. We want to make sure we get the right strength/product. Does anyone know a place online we can get just a pound to start with and make sure it will work for our ore? We found one site, and this was the description...is it what we need? 
Sodium Sulfide Nonahydrate, Crystal, Reagent Grade, 500 g (how does this translate on ounces or pounds?)

We also found two places on Amazon that have it in a one lb container. Here's the only descriptions they have:
SODIUM SULFIDE REAGENT 100G $15.95

Photographer's Formulary Sodium Sulfide 1 pound by Photographers' Formulary
Buy new: $8.95


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## goldsilverpro

Hey Ferrell, off the subject but, my middle name is Ferrel and my Dad's 1st name was Ferrel. Not many of us out there. Scottish, I believe.

Christopher Ferrel Owen

maybe, Christopher O'Ferrel O'en


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## Ferrell

Interesting! It's our last name. My first name is Miralee, my husband is Allen. We met a hotel clerk who's mother's first name is Ferrell. Very different for a woman!


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## sawmill

Ferrell

You are in luck,I just happen to be able to help.
You can get sodium sulfide by the pound at Hi Valley Chemical.
Yes you can order it on line too. It is $9.96 ,but beware that it is
listed as hazmat .The shipping charge is $19.24.

It is tech grade,and it really does a good job. Hi Valley is located
in Salt Lake City, Utah. Here is their web site WWW.hvchemical.com.
They carry every thing you will need for Thio leaching. Their prices
are better with larger quantities.


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## Harold_V

Ferrell said:


> Sodium Sulfide Nonahydrate, Crystal, Reagent Grade, 500 g (how does this translate on ounces or pounds?)


453.6 grams = 1 pound avoirdupois.

Harold


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## Ferrell

sawmill said:


> Ferrell
> No you can reuse the leach over and over,by recharging with sodium
> sulfide. You may have to add a little ammonia,or ammonium sulfate
> to bring the PH to 9.2.
> 
> A good PH meter will be your best friend.



I'm only responding to the items in this post that I was unsure of, and hoping someone can tell me the answer, since I've noticed sawmill hasn't been active on the forum for some time. 

We've made thio leach before, using thiosulfate, ammonium sulfate and copper sulfate, but recently realized my husband had premixed a batch of concentrate, and the copper sulfate (being so fine) would settle in spots in the canister. We worried we didn't have ratios correct so today we did a batch (3 gals of water) using the three ingredients. Wow, what a difference! When we did it before we must have had a much higher % of the thiosulfate, as our ph was always up around 8.5 after adding our ore. This time it was about 7.7....we thought adding ammonium sulphate would raise the ph, but it drops it quite a bit. We had to add a lot more ammonia to the mix than we've ever done to get the ph up to 9.0. 

We do have an excellent, professional ph meter, so no worries there, and we keep new packets of buffer on hand to make sure it's always accurate. 

We're also running this time at 105 F (we did it at 80F on past runs but understand it's supposed to be warmer than that--we may try it at 110-120F next time if needed) and we're injecting air and mixing continuously as well. We'll be running for on hr, letting settle, draining off and adding sodium sulfide to drop the metals. 

We did a small test last night on some leach we'd already ran (but not at that temp and not with the correct mix) and added the sodium sulfide. It immediately turned dark gray and started dropping, but we never saw the ph go down. I know it's supposed to drop VERY fast, and then the ph will shoot up. Is it possible that the ph meter just didn't have a chance to register the drop before it went up? It went from 7.7 (it had dropped ph on its own as it sat for 24 hrs) up to 8.3 after adding the sodium sulfide. We understand we're supposed to 'shock' the leach by adding the sodium sulfide so it will drop the gold, and that the ideal ph is 7 to take it to so it will drop the gold/pm's, but it never showed a drop on the ph....that's our major concern. 

Anyone know? 

And yes, we've read the patent on thiosulfate, and from what we could tell it shows the higher temps for mixing, the air induction, ect.


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## kjavanb123

Juan Manuel Arcos Frank said:


> Sawmill:
> 
> Secret fromula?..Here,in this Forum,there are no secrets.
> 
> Do you want to know how I regenerate thiosulfate to use it again and again?...let it be:
> 
> The process is too simple,just let settle down the black mud(silver or gold),siphon the liquid,filtrate the black mud with silk fabric(I do not know the name in USA,but here in Mexico is called "Molletón",used to make curtains and pillows),collect all the liquid and add some sodium sulfite,it destroys sodium sulphide´s leftovers(because Na2S smells bad) and thio is ready for reuse.
> 
> My customers are happy to use this process because they do not have to buy any fixer.Of course,there are people really upset with me,who are they?,well,bad guys,all of them,like Kodak,Fuji,Russell and a long so for because they are not able to squeeze my clients anymore.
> 
> Kindest regards.
> 
> Manuel



Hola Manuel,

I really used your methods like the oxalic acids for x-ray films with success. I am trying to process pins collected from connectors and slots off the motherboards using sodium thiosulphate, please kindly advise on the ratio of water to sodium thiosulphate and also once all the gold plating is removed I assume it means that the process is done correct? I couldn't find any info of thio leach on pins mostly on ores.

Thanks and best regards,
Kevin


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## solar_plasma

> it's a fairly selective leach



Can anyone tell more or give links about its selectivity?


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## kjavanb123

All,

As I was searching for a description on thio leach I came accrods the attached document, it seems very useful, please kindly advise.

http://actamont.tuke.sk/pdf/2011/n2/2ficeriova.pdf


Regards,
Kevin


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## GoldHappy

There's been a lot of talk and even some awesome links to information using thiosulfate leach on circuit boards, but we're wanting to use it on finely crushed ore. We've experimented with it a lot, changing the formula slightly on the amt of sodium thiosulfate, as well as the copper sulfate, and adding a quantity of ammonium sulfate. We've had limited results on extracting gold, but not consistent. One of the things we've read over and over is that the ORP needs to be on the plus side, preferably above 140, while the pH should be between 8 and 10.5, with the optimum being 9.5--10.5. The pH can be brought up using ammonia, but doing so drops the ORP into the negative range. We've not found a way to keep the ORP and the pH up at the same time. Before we knew anything about keeping the ORP up we only concentrated on the pH range, and again, we did have some limited success, but would love to know if anyone has more exact information on the formula as regards to ore, pH and ORP values.

Thank you!


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## butcher

GoldHappy,

I am sure you have studied many documents have you seen this one.
http://qspace.library.queensu.ca/bitstream/1974/5465/1/xia_chen_200809_phd.pdf

Have you tried any small controlled experiments, like with just a more pure gold metal and the thiosulfate leach, to determine what works best to just dissolve the gold, without the other complicating factors of the ore involved, and then adding ore in these tests to see how that effects the experiment.


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## Ian_B

Manuel I have been doing a lot of reading in regards to Thiosulfate solutions and have read a number of your post in regards to silver sulphide/ sulfide from dropping the silver in thiosulfate solutions as a sulfide to conversion of the silver sulphide with potassium nitrate or re-bar. Also on page number 85 of Hoke's for dropping the silver it says


> When silver is to be recovered from ordinary quantities of old hypo baths, such as accumulated in the average photo shop, the commonest procedure is to add sodium sulphide, which immediately precipitates the black silver sulphide; the liquid is discarded...



I am a little confused though because of the two posts below that I am quoting where you mention to use Sodium Sulfide on page 3 of this thread if if you want to reuse/ rejuvenate the thiosulfate solution, but then in your last reply you say to use Sodium Sulfite.



> Secret fromula?..Here,in this Forum,there are no secrets.
> 
> Do you want to know how I regenerate thiosulfate to use it again and again?...let it be:
> 
> The process is too simple,just let settle down the black mud(silver or gold),siphon the liquid,filtrate the black mud with silk fabric(I do not know the name in USA,but here in Mexico is called "Molletón",used to make curtains and pillows),collect all the liquid and add some *sodium sulfite*,it destroys sodium sulphide´s leftovers(because Na2S smells bad) and thio is ready for reuse.
> 
> My customers are happy to use this process because they do not have to buy any fixer.Of course,there are people really upset with me,who are they?,well,bad guys,all of them,like Kodak,Fuji,Russell and a long so for because they are not able to squeeze my clients anymore.
> 
> Kindest regards.
> 
> Manuel





> No,no,no!!!!!!...Sodium sulfite is Na2SO3,sodium sulphide(or sodium sulfide) is Na2S,they are different salts.Sodium sulfite is a white powder,sodium sulphide is a yellow powder(or flakes,anyway)...*sodium sulphide* is the right stuff to precipitate silver(or gold) from thiosulfate´s solutions,besides,it regenerates thiosulfate solution to continue using it again and again.
> 
> BTW,keep your eyes open when using sodium sulphide,if pH is low(below 6) hydrogen sulphide(H2S) could be formed and released,it smells like rotten eggs and it is very toxic.
> 
> Kindest regards.
> 
> Manuel



To add to the confusion In this thread http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=17927&p=182051#p182051 started by nh6886 you give directions on how to make Sodium Sulfide for this method of reusing the Thiosulfate. 

I believe that sodium sulfide is what I am looking for but before I purchase or make what I need I wanted to ask for a little clarification. 

Thank you a bunch Manuel and or anyone else who would like to chime in


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## Juan Manuel Arcos Frank

Ian_B:

Sodium sulfite(Na2SO3) is added to the regenerated fixer solution just to eliminate rotten eggs odor.

Kindest regards.

Manuel


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## Ian_B

Thank you Manuel for your reply. I just want to go over this.

If I had a solution of Sodium Thiosulfate that also contained Silver in solution( if I am correct Silver Thiosulfate)and solids of Silver sulfide I would first decant the solution from the silver sulfide. I would then treat the solution with Sodium Sulfide to precipitate the silver in solution as Silver Sulfide and to rejuvenate the solution. After precipitation I would add Sodium Sulfite eliminate the rotten egg odor?

I think it's a language barrier that is causing the uncertainty on my part 

Thank you again Manuel 


Ian


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## solar_plasma

Juan Manuel Arcos Frank said:


> Ian_B:
> 
> Sodium sulfite(Na2CO3) is added to the regenerated fixer solution just to eliminate rotten eggs odor.
> 
> Kindest regards.
> 
> Manuel



I haven't read the whole thread, but Na2CO3 is sodium carbonate, washing soda, not sulfite.


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## Juan Manuel Arcos Frank

Yes,Sir...I am such an idiot!!!!....Na2SO3 is the right formula for sodium sulfite.I wrote Na2CO3 instead of Na2SO3.Thank you,Solar_plasma.I am correcting the original post.

Kindest regards.

Manuel


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## Juan Manuel Arcos Frank

Ian_B:

Yeah,you are right.

Before filtering the solution,I mean,once Ag2S is on the filter,add a little bite of Na2SO3 to the regenerated fixer solution just to eliminate nasty odor.

It is not funny working developing films in a dark room that smells like rotten eggs.

Kindest regards.

Manuel


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## Mud Dobber

I am new to this forum . but I have done a lot of research on thio leach.. You may have already seen this , but I think we could all learn a lil something from this . Lab test results are from 2003 but since I found this ,every batch has dropped nice values of gold and pgms, no matter soil composition.. http://www.ejmpep.com/rath_et.al.pdf 
I did alter the ratio and added water for volume
Caution!!! this is highly caustic.. wind is your friend  
6 oz ammonia thio
1 gal water (tap not distilled) ph will be ajusted next
20 plus % ammonia hydroxide .. bring ph to 10 or higher
slowly add sodium hydroxide to a ph of 11.3 is optimal I know hard to reach. I usually run between 10.4 and 10.8 Dont go higher than 11.3 !!!
At the suggested ph of 9.2 you have to constantly check ph. Mine never dropps below 10 during a run! 
I do live in SC so ther is copper in all my material. You may have to add a catylist if your material doesnt have it naturally.. 
HAPPY HUNTING YO
Oh yeh, sometimes it takes a some time and a few tricks to get all the goods out of the solution. As much as a month in some materials. 
I know, still a lot of work. As they say, If it was easy, everyone would be doing it ..


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