# a new plan



## Geo (Jan 29, 2014)

I have decided that i will try to do a sodium thiosulfate leach on gold and precipitate the gold with copperas or a very fine steel wool. First, i am planning to make my own thiosulfate leach by adding sulfur to a boiling solution of NaOh. After carefully filtering the hot solution, crystals of sodium thiosulfate will drop from solution upon cooling. A good non-magnetic stainless steel pot should work for this. For a ratio of 6 parts NaOh and 4 parts sulfur, the formula is pretty simple. I can source the sulfur and NaOh locally as Dudadiesel has actually moved closer to my house. For about $40, I can buy enough of both chemicals to make about 10 pounds of crystals. When the weather breaks and i can work outside, i have bought a small sample of both chemicals (4 OZ sulfur USP and 16 OZ of NaOh) and with these using 6 to 4, i should make around 8 OZ of crystals. Using distilled water to make the leach, i will saturate the solution with as much gold as it will hold. By precipitating the gold and melting, it will give me a ball park estimate of what I can expect from my own chemistry. I will record everything and quite possibly make videos of as much of it as i can. If this works as well as i hope, i will try the leach on incinerated chips next to see how it will work on bonding wires. Processing chips this way is what led me to try this. Pulling the gold from the ash without pulling out the other metals first would be great.

This may be old stuff to some people here but its brand new to me. Any thoughts would be helpful.


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## Loito (Jan 29, 2014)

I wondered about the way you would make your thiosulfate. Thiosulfate is produced by the reaction of sulfite ion (hot solution) with elemental sulfur, by incomplete oxidation of sulfides (pyrite oxidation) or by partial reduction of sulfate. In my opinion sulfur will disproportionate in hot NaOH to sulfide & sulfite. Of course in sulfidic solution it will form polysifides and in a solution containing sulfite it will become thiosulfate. 

Perhaps the separation will be difficult or the purity bad. Have you already tried your route?


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## artart47 (Jan 29, 2014)

Hi Geo!
This is cool! I'm curious to see how it works. Hearing that chemistry sure brings back memories. When I was like eleven years old, I was reacting NaOH with sulpher and it would make what they called sodium polysulphite. I'd then add ethylene dichloride and like magic it would drop a ball of white rubber. I would warn you! It was the stinkiest stuff you could ever imagine. I poured the remaining liquod down the basement floor drain and it took years for the nausiating oder to leave .
artart47


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## solar_plasma (Jan 29, 2014)

You will first need to neutralize the NaOH with SO2, then you have Na2SO3, which then can be boiled with sulfur to form Na2S2O3 ... if wikipedia is right.


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## Geo (Jan 29, 2014)

from wiki:

Industrial production and laboratory synthesis

On an industrial scale, sodium thiosulfate is produced chiefly from liquid waste products of sodium sulfide or sulfur dye manufacture.[2]
In the laboratory, this salt can be prepared by heating an aqueous solution of sodium sulfite with sulfur or by boiling aqueous sodium hydroxide and sulfur according with the following equation:[3]
6 NaOH + 4 S → 2 Na2S + Na2S2O3 + 3 H2O
Upon cooling sodium thiosulfate crystallizes out of solution.


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## solar_plasma (Jan 29, 2014)

If Na2S is just a little bit like K2S, maybe you will not love it. It generates H2S with moisture, at least when it is solid. Though in solution it reacts slowly with H2O and O2 to thiosulfate. Might work well. Hard to say which one of the two is the nicest process. To me it seems both of them are harder to do than to read.


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## Geo (Jan 29, 2014)

im thinking that the Na2S, being more soluble than the thiosulfate, will stay in solution. since i will only use enough water to dissolve the NaOh, the excess H2O produced in the reaction will lock up the Na2S.

really, the only way to find out if it will work is to try it and find out. i was hoping to hear from someone that has actually tried it. i can totally understand if its being kept as a secret but sooner or later, someone like me will figure out how to make it work. 

the secret is not that sodium thiosulfate will leach gold more than it is with how to recover the gold from the solution without contaminating it with massive amounts of sulfur. electrolysis is one method for removing the gold and being able to re-use the solution. im not as interested in re-using the solution as i am about the concept of reclaiming visible gold (or unseen gold) from Escrap. im not expecting to start a revolution in the hobbyist refining niche as much as i am furthering my self education.


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## Platdigger (Jan 29, 2014)

40 dollars seems a bit much for 10 pounds.
I paid around 1.50 per pound or less for sodium thio in a 50 or 55 pound bag.


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## Geo (Jan 29, 2014)

Platdigger said:


> 40 dollars seems a bit much for 10 pounds.
> I paid around 1.50 per pound or less for sodium thio in a 50 or 55 pound bag.



thats just a rough estimate. i cant find a good source nearby.


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## NoIdea (Jan 29, 2014)

Hey Geo, like the way yer thinking 8) 

Check out this paper, a wee bit heavy in parts, butt yer on the right path me thinkith.

http://web.anl.gov/PCS/acsfuel/preprint archive/Files/35_4_WASHINGTON DC_08-90_1392.pdf

Good luck

Deano


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## Geo (Jan 29, 2014)

so figure 3 on page 9 shows the reaction times at different temperatures. that is some useful information to have.

thank you Deano, very much.


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## Loito (Jan 30, 2014)

Hoi,

I have browsed my documents and I found a review paper about that process. Enjoy the reading 8)


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## solar_plasma (Jan 30, 2014)

Quite amazing those leaching methods, I enjoy this thread!

Something I never understood is, under what conditions are they the preferred methods? Maybe, when the gold content of the source is low like in ores and you have to use a lot of liquid? How is cementation prevented? Is it like in a filter, when you "wash" by pouring fresh water on the top?


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## Loito (Jan 30, 2014)

Both methods have their advantages and disadvantages. Both dissolve gold faster than cyanide, have a better efficiency in the leaching rate, can better handle difficult ores and low concentrations (where cyanide might have some troubles), selectivity is higher and be more energy efficient (especially thiourea since it is better at low temperatures than at higher ones). 

BUT the main problem is, and this is also the reason why it is not really used in the industry, is that the chemical consumption is higher than in the cyanide process, which leads to higher costs and so on.

Another difficult is the recovery of the gold from the solution. This processes still need some R&D to be really interesting for the industry. 

And yes you are right, this methodes are really interesting!


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## butcher (Jan 30, 2014)

What I gather from studying these alternative leaches used to try and replace cyanide, is they were not widely used in the industry, I see a lot of papers or study on them, but not a whole lot of use, they also seem to be leaches that are very hard to keep the leaching process working properly, with sodium thiosulfate and gold keeping the pH, concentration, ammonium complex and copper catalyst, oxidizer, and everything in the proper proportions seem to be a very difficult task, there are a few members here that have used, or tried to use the process, and from what I can gather they had a very difficult time keeping the leach within the working limits.

Cyanide although slower seemed to work extremely well, I still do not see where these other leaches have been able to replace cyanide.

sodium thiosulfate I feel would make a better leach for silver ore that has been converted to silver chloride after a chloridized roasting process, here it seems to have worked well, but for leaching gold ore the process seems be just riddled with difficulty...

I agree with Loito, I find them interesting, but I do not see where they have been proven the best alternative to leaching gold from ore over the proven cyanide process, and with the difficulty in keeping the leach in the parameters where it works to leach the gold, just a problem not easy to deal with.


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## Geo (Jan 30, 2014)

Thank you Loito, that is a very nice document and i will read it fully. Reading through some of the pertinent information, some things jump out at me. This document was written on leaching ore and not necessarily for Escrap. The problems that might arise from leaching from a source material already high in sulfates (ores), may not be an issue since i will be using things like bare pins and fingers and (hopefully) incinerated chips. Instead of maintaining a PH of 10 to 10.5, i am planning on keeping the solution as basic as possible to reduce the attack of base metals. Actually bringing the PH down to 10 will let me be able to cement the gold out of solution using steel wool and since ferrous sulfate is acidic already, should precipitate the gold directly. Of course this will render the solution unusable for further leaching. I may try adding a little copper oxide as an experiment to gain more speed if necessarily, but the videos ive seen of the reaction, it happens fairly quickly.

To tell the truth, cyanide scares the hell out of me and sodium thiosulfate is non-toxic. For me, its either this or sticking with the older tried and true methods of AP and AR.


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## 4metals (Jan 30, 2014)

Both silver and gold will come out in a steel wool canister. Then melting the sulfide residue in the canisters with iron will yield a mixed bar. From there its easy.


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## modtheworld44 (Feb 2, 2014)

Geo

Mr Maxwell House had his silver and Gold baby of 0.2grams.I went back and electrocuted him again and now I'm waiting for his stomach to settle out again.I'm hoping to get a better weight from this next baby!LOL It works.Good luck on your end!



modtheworld44


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## freechemist (Feb 4, 2014)

*@ Loito*: Thanks for this very interesting, well founded review, which confirms a few practical experiencies I gathered in leaching and recovering gold and silver with/from cyanide-solutions and with the silver-thiosulfate-system ("green" and "black" photographic films).

*@ Geo*: I have no doubt that you will reach your goal, to produce your own sodium thiosulfate, and that it will work in the dissolution of gold. However, recovering the gold from thiosulfate-leach in an economically feasible way, is a different matter. There is only scarce experience, and according to the reviews authors, a lot of research-work will still be needed, surmounting our capabilities as hobby-refiners.


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## johnny309 (Feb 4, 2014)

On this process I would like to mention two major drawbacks(in the hobby department):

1) monitoring the PH(time consuming,giving the fact that the process is a long.
2) cost of (let's say fuel) to keep the solution warm (between 40-60 C)

P.S: In the papers I do not see the involvement of Sn....this can cause some consumption of reagent(thiosulphate).


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## Geo (Feb 7, 2014)

ok, i had to scrap the plan to make my own thiosulfate. it takes too long and you have to stay with it. since its not too unreasonable on Ebay, i just ordered a couple of pounds of crystals. after reading on this patent : http://www.faqs.org/patents/app/20100111751#b i have decided that it is going to be more steps to the final product but with less time spent in the end. the two main components of the lixiviant (thiosulfate and ammonia) are easy enough to obtain. oxygen from the air and the formula calls for copper sulfate. i will buy a 1 pound can of root killer tomorrow. any thiosulfate can be used for the lixiviant but sodium thiosulfate was recommended. if i can make this work, i could very well start a small scale gold refinery here, using incinerated boards as my stock material. i know junk people from since i could walk thats still in business.


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## kurtak (Feb 8, 2014)

This sounds interesting - I've read about it as an alternative for leaching ore's (along with SSN as an alternative)

My question is with incinerated electronics how does tin factor in - is it going to cause a loss due to colloids if not removed first?

Kurt


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## Geo (Feb 9, 2014)

Ok guys, here's an update. The first part of my experiment was a huge success. I wanted to strip the gold from plated pins. The photos below are the pins after stripping. I placed the same weight in unstripped pins beside them to show the difference in color. The pins are not discolored, the gold has been removed. The silver color is the nickel barrier metal. The solution is a total wreck. I wont describe what i did until i can reproduce the effect without all the back tracking. Recovering the gold from solution is secondary to being able to put it into solution for me. I know that for a fact, I can get the gold out of solution.


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## cnbarr (Feb 9, 2014)

Nice work Geo, I tried sodium thiosulfate Leach a couple of years ago, with less then stellar success I abandoned the project. With what I've seen in your thread has inspired me to try again!


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## modtheworld44 (Feb 9, 2014)

cnbarr said:


> Nice work Geo, I tried sodium thiosulfate Leach a couple of years ago, with less then stellar success I abandoned the project. With what I've seen in your thread has inspired me to try again!



cnbarr

I'm getting pretty good results with my ammonium thiosulphate.I've been experimenting with it since Jan 20 and I got mine free with some free precious metals to boot.


Geo 

Did ace have that ingredient? If so for how much?



modtheworld44


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## Geo (Feb 9, 2014)

Ace Hardware brand Ammonia janitorial strength formula, 10% ammonium hydroxide. I actually added too much copper by accident and bubbled 96% oxygen through it all night. This morning, the solution was blue with green copper oxide solids. I have my overflow that i added hcl to and it dropped all metal from solution. The solids from the overflow solution looks like copper (brown powder). Ill digest the solids from the overflow and incinerate the metals from the main solution and then digest the solids from that and test to see where the gold ended up. At least i will know if I was removing gold before the overflow or after.


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## goldenchild (Feb 10, 2014)

Patiently waiting 8)


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## freechemist (Feb 13, 2014)

February 9th, 2014 Geo wrote:


> Ok guys, here's an update. The first part of my experiment was a huge success. I wanted to strip the gold from plated pins. The photos below are the pins after stripping. I placed the same weight in unstripped pins beside them to show the difference in color. The pins are not discolored, the gold has been removed. The silver color is the nickel barrier metal. The solution is a total wreck. I wont describe what i did until i can reproduce the effect without all the back tracking. Recovering the gold from solution is secondary to being able to put itbinto solution for me. I know that for a fact, I can get the gold out of solution.


It's worth while to reread the posts written on the topic *"Thiosulphate Dropped--Testing for PM?"*, begun about 2 years ago:

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=12284.

It's all about thiosulfate-leaching, followed by recovery of gold with iron(II)sulfate.


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## Westerngs (Feb 13, 2014)

You can get concentrated sodium or ammonium thiosulfate solution at a camera shop. Buy Kodak black and white fixer, somewhere around $10 for enough to make about 5 gallons solution.


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## niteliteone (Feb 14, 2014)

I have found my nitric supplier also carries it (sodium thiosulfate) for what I feel is a reasonable price.
http://www.sierrachemicalcompany.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=741&category_id=6&keyword=thiosulfate&option=com_virtuemart&Itemid=2


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## solar_plasma (Feb 14, 2014)

Did you use only sodium thiosulphate in your leach or the method with ammonia and CuSO4?


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## Geo (Feb 14, 2014)

the lixiviant was sodium thiosulfate, ammonium hydroxide, and the patent i followed said to use any copper solution so i added 5mil copper nitrate. i know the nitrate kills the thiosulfate but it was a very small percentage and the patent named copper nitrate specifically. it only takes a very small amount of copper to get the reaction. copper sulfate is recommended but any copper solution will work.


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## solar_plasma (Feb 14, 2014)

http://www.tandfonline.com/doi/abs/10.1080/10473289.2003.10466230

...maybe useful. In this abstract above they tell the concentrations used in the three leaches to extract most basemetals first (H2SO4), then pm's (thio) and at last Pb (NaCl/HCl?). Sn is not mentioned, but according to http://actamont.tuke.sk/pdf/2011/n2/2ficeriova.pdf, it will be leached together with Pb.


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## Geo (Feb 14, 2014)

Thank you solar_plasma, this is not going to be like mixing a cake recipe. :shock: It's like learning a new language for me as i have no chemistry background. I will eventually have enough numbers to formulate a recipe type process for the chemistry challenged. There are some things I am working out. Like sodium thiosulfate is 148.21 g/mol. and water is 18.015 g/mol. At a 0.2 m solution, how many grams of sodium thiosulfate pentahydrate would i need for 20 liters of solution.


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## FrugalRefiner (Feb 14, 2014)

Geo said:


> There are some things I am working out. Like sodium thiosulfate is 148.21 g/mol. and water is 18.015 g/mol. At a 0.2 m solution, how many grams of sodium thiosulfate pentahydrate would i need for 20 liters of solution.


I'm not sure if you were actually looking for an answer, but...
We know that the sodium thiosulfate = 148.21 g/mol.
Since it's a pentahydrate, we have 5 water equivalents per mole of sodium thiosulfate, so multiply the 18.015 times 5 for a water weight of 90.075 g/mol.
So the total weight of one mole of sodium thiosulfate pentahydrate is 148.21 + 90.075 = 238.285 g/mole.
Now if we wanted to make 1 liter of 1 molar solution, we'd use 238.285 grams. 
For one liter of .2 M solution, we'll need 1/5 that amount = 47.657 grams. 
For 20 liters, multiply 47.657 * 20 = 953.14 grams.
EDIT
GSP has pointed out that the molecular weights I used are incorrect.  You can see the correct weight in his post later in this thread. 

Dave


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## Marcel (Feb 15, 2014)

The most exiting thread in a long time! I can not contribute anything here, since I have zero practical experience with thyiosulfate recovery, but I did follow the concept for a long time now, because it appears to be a relatively safe cyanide alternative. Please keep us updated! Also please consider possible toxic or other hazards with the remaining substances and how they should be treaded/disposed in an enviromentally correct way! Maybe an analysis of the waste would clearify the required "skill level" of this process.


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## Geo (Feb 15, 2014)

Actually, I was working on trying to figure it out through studying on my own but after 3 hours of reading and studying, I came up with wildy different outcomes. I really appreciate the answer. It's going to take some studying for quite some time before I'm able to formulate chemical equations. I will keep trying to figure out these things for myself but it is awesome that you guys are here to help me out. 

Thank you Dave, It may have taken me months of studying to find the answer myself.


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## solar_plasma (Feb 16, 2014)

I wanted to know, if only Na2S2O3 alone will oxidize gold, so I did put some goldplating into a about 10% solution. After some days the colour has actually changed, which could be a sign for gold is dissolving. This may not have some practical use, just a curiousity. If it in some weeks will dissolve completely I will add the pics to this post.


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## Loito (Feb 16, 2014)

> I wanted to know, if only Na2S2O3 alone will oxidize gold, so I did put some goldplating into a about 10% solution. After some days the colour has actually changed, which could be a sign for gold is dissolving.



"In the absence of ammonia, gold dissolution by thiosulfate is passivated by the build up of sulfur coatings as a result of decomposition of thiosulfate on the gold surface (Pedraza et al., 1988; Jiang et al., 1993; Chen et al., 1993)."

"The oxidation of thiosulfate in aqueous solution by molecular oxygen, under ambient conditions of temperature and pressure, is known to be extremely slow and only occurs when copper (II) ions and ammonia are present (Naito et al., 1970)."

I have copied these two passage from the paper, which I have uploaded. I do not want to destroy your hopes, but i think it would take a while.

By the way. I finally started my expermiments on a thiourea leach. The leaching looked very promising. Tomorrow my steel cathodes will arrive and I try the electrowinning tests. I will start e new threat for that in a few days with some pictures.


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## solar_plasma (Feb 16, 2014)

Then the change in colour on the right may be caused by this passivating layer. Thanks for the explaination!


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## bmgold2 (Feb 16, 2014)

Loito said:


> > By the way. I finally started my expermiments on a thiourea leach. The leaching looked very promising. Tomorrow my steel cathodes will arrive and I try the electrowinning tests. I will start e new threat for that in a few days with some pictures.



Please do. A few/several years back, I bought Charles Butler's book on Nitrate Leaching and he uses thiourea and also plain urea for his nitrate leaching. I've never done many tests with it though. I know the thiourea is a carcinogen. The directions I have used very weak solutions of it though. I'd have to check but I'm thinking it was like 0.1 percent. He also used zinc powder to recover the gold. I have never been able to find out if the leaching solutions can be tested with stannous chloride. It always seemed like a lot of work to do the 5 or 10 minute quickie leaches and then have to do the torch assay to see if you had ANY gold in the solution.


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## goldsilverpro (Feb 16, 2014)

Geo said:


> Thank you solar_plasma, this is not going to be like mixing a cake recipe. :shock: It's like learning a new language for me as i have no chemistry background. I will eventually have enough numbers to formulate a recipe type process for the chemistry challenged. There are some things I am working out. Like sodium thiosulfate is 148.21 g/mol. and water is 18.015 g/mol. At a 0.2 m solution, how many grams of sodium thiosulfate pentahydrate would i need for 20 liters of solution.


Anhydrous sodium thiosulfate, Na2S2O3, is 158.13g/M. Sodium thiosulfate pentahydrate, Na2S2O3.5H2O, is 248.21g/M. Therefore, the pentahydrate is only 158.13/248.21 = .637, or 63.7% sodium thiosulfate..

0.2M of 248.21g/M is 248.21 x .2 = 49.6 g/liter. 20 liters would require 49.6 x 20 = 992g of the pentahydrate.


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## FrugalRefiner (Feb 16, 2014)

Sorry Geo.  I didn't check the molecular weights you provided for the thiosulfate and water molecular weights, so I'm afraid I led you astray in my calculation.

I'm going to edit my original post in this thread.

Dave


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## Geo (Feb 16, 2014)

Thanks Goldsilverpro. We finally warmed up and thawed out. Now i can get back to experimenting. 8)


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## Hoad413 (Feb 17, 2014)

How much urea is needed to dilute nitrice acid?

Say I have 30ml of nitric acid in my ar along with 120ml of hydrocloric acid

How much urea would be needed to dilute the nitric acid to a ph 1.0?

How do I go about doing this proses do I just use urea on it's own or do I also need to add water?
Thank you


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## butcher (Feb 17, 2014)

Urea will not dilute nitric acid, water can be used to dilute nitric acid.
urea will not destroy nitric acid if mixed with nitric acid it can make a dangerous substance of urea nitrate, a small amount of urea will destroy NOx gases in nitric acid.

In my opinion you should not use urea to remove nitric acid from an aqua regia solution, it will not destroy free nitric acid, although it can destroy decomposed nitric acid in solution (if you did not do what most new people do and use too much nitric acid), urea will just add more contamination, and can possibly cause a dangerous solution either in the recovery process or even in the waste treatment process, it will also cause problems if you have platinum group metals involved where the urea can decompose to ammonium compounds...


My suggestion is forget about using urea or studying how much you need, instead learn to refine where you do not need urea.

Use only the bare minimum amount of nitric acid needed, so that at the end of the process you have no free nitric acid to get rid of.

Use the evaporation method taught by C.M.Hoke.

Use gold to remove free nitric from the solution (Harold's gold button trick). 

Use sulfamic acid to remove free nitric acid.

Learn to recover and refine gold, study Hokes book and the forum...


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## Geo (Feb 17, 2014)

No worries Dave, it was my fault. You were still closer than me. :lol: Please feel free to offer any help that you can, and I will try to check my numbers before i post them.


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## solar_plasma (Feb 25, 2014)

After reading "THIOSULFATE LEACHING OF GOLD--A REVIEW" several times I believe I am starting to understand ammonical thiosulfate copper system:

a) Leaching gold and silver will work best around Eh 0,3eV and pH 9,5. Depending on the setting, the range can be more or (mostly) less wide.

b) The pH is modified by NH4OH.

c) The Eh is determinated by the concentrations of all electrolytes dissolved. 


Can anyone tell, if this is correct so far?


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## Loito (Feb 25, 2014)

(a) Yes, most leaches carried out at near pH 9-10 to allow free ammonia to be present to complex copper (II) and reduce the interference of some foreign cations such as iron or manganese.

(b) Yes

(c) I am not sure what you exactly mean. For effective gold dissolution an oxidation potential between 150-250mV vs SHE is required (depending upon pH). At higher potentials there is significant oxidation of thiosulfate to tetrathionate. But Gold thiosulfate is reduced at -0.15V vs SCE and is independent of pH for values above 4.


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## solar_plasma (Feb 25, 2014)

Loito said:


> (a) Yes, most leaches carried out at near pH 9-10 to allow free ammonia to be present to complex copper (II) and reduce the interference of some foreign cations such as iron or manganese.
> 
> (b) Yes
> 
> (c) I am not sure what you exactly mean. For effective gold dissolution an oxidation potential between 150-250mV vs SHE is required (depending upon pH). At higher potentials there is significant oxidation of thiosulfate to tetrathionate. But Gold thiosulfate is reduced at -0.15V vs SCE and is independent of pH for values above 4.




oooops ...I meant 0,3V ...don't know how I came to write eV... *shaking head*

Thank you, then I got the most basical basics!


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## a_bab (Feb 25, 2014)

Question for those who made the thio leach: does it stink like ammonia? 

I'm afraid it does since there is some free ammonia and it is supposedly used at 40-50 degrees C (ammonia leaves the solutions quite fast in these conditions).


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## butcher (Feb 25, 2014)

The ammonia (besides being basic pH ) is to form a copper amine complex which acts as a catalyst for the reaction.
Cu (2+) + 4NH3 --> Cu(NH3)4

Oxidation of gold by the cupric amine.
Au + Cu(NH3)4 + 5 S2O3 --> Au(S2O3)2 + Cu(S2O3)2 + 4NH3
(here most of the ammonia is still in solution)

Oxidation of cuprous thiosulfate back to cupric amine.

Cu(S2O3)3 + 4NH3 +1/4 O2 + 1/2 H2O --> Cu(NH3)4 + 3S2O2 + OH-

Gold forming thiosulfate complex.
Au + 2 S2O3 + 1/4 O2 + H2O --> Au(S2O3)2 + OH-

Copper and ammonia acts as the catalyst.

Loss of the thiosulfate from formation of polythiontes, oxidation from cupric amine oxidizing thiosulfates is a problem...

2Cu(NH3)4 + 8S2O3 --> 2Cu(S2O3)3 + S2O6 + 8NH3
(Here is where you may smell ammonia released).
Also problems of Oxidative degeneration of thiosulfates by oxygen to polythionates S2O6, S6O6...
Which rob solution of thiosulfate.

Other oxidations involved
Tetrathionate formation.
S2O3 + 1/2 O2 + H2O --> S4O6 + 2OH-
Tri-Thionate formation.
3 S4O6 +5/2 O2 + H2O --> 4S2O3 + 4H+

Sulfite formation.
S2O3 + 2 O2 + H2O --> 2SO4 + O2 + 2 H+

Ammonium back to ammonia.
NH4 + OH- --> NH3 (aq) + H2O --> NH3(g) + H2O
Here you may smell the ammonia fumes.

Also notice hydroxides and acids forming in the solution make keeping pH in range to keep the leach working properly becomes a challenge.


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## Geo (Feb 25, 2014)

Im glad sometimes that it's hard for me to follow chemical equations. If i weren't so ignorant, I may never try to do things for myself. :lol: So when i ran concentrated O2 through the solution all night, i was just wasting the thiosulfate solution. This process is one that needs close inspection and regular PH testing. Will this meter hold up to the basic solution to use for this? http://www.ebay.com/itm/Digital-PH-Meter-Tester-Pocket-Aquarium-Pool-Water-Wine-Urine-LCD-Pen-Monitor-/310807986488?pt=US_Garden_Tools&hash=item485d998138


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## niteliteone (Feb 25, 2014)

Geo,
I have a Ph meter just like that one.
They are great for hydroponics, but Not for the strong acids we use.
They will work a time or two, if you don't wait a week between tests.
Mine failed during the second test.


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## Geo (Feb 25, 2014)

niteliteone said:


> Geo,
> I have a Ph meter just like that one.
> They are great for hydroponics, but Not for the strong acids we use.
> They will work a time or two, if you don't wait a week between tests.
> Mine failed during the second test.



I'm so silly, I almost posted one of those "here's your sign" things. :lol: There should be no acids involved in testing this solution. Your main worry would be whether the tester can hold up to the BASIC solution. Strong bases can be just as hard on some metals as acids so this is my question, will this tester work on a basic solution?


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## butcher (Feb 25, 2014)

I have one of these from Hanna HI 198129, I have had it several years and still have not had a problem with it.

http://www.hannainst.com/usa/prods2.cfm?id=030&ProdCode=HI%2098129


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## Loito (Feb 26, 2014)

> The ammonia (besides being basic pH ) is to form a copper amine complex which acts as a catalyst for the reaction.
> Cu (2+) + 4NH3 --> Cu(NH3)4
> 
> Oxidation of gold by the cupric amine.
> ...



I have corrected some mistakes in your equations.

Au + Cu(NH3)42+ + 5 S2O32- --> Au(S2O3)23- + Cu(S2O3)35-+ 4 NH3
(here most of the ammonia is still in solution)

Oxidation of cuprous thiosulfate back to cupric amine.
2 Cu(S2O3)3 + 8 NH3 +1/2 O2 + H2O --> 2 Cu(NH3)4 + 6 S2O32- + 2 OH-

4 Au + 8 S2032- + O2 + 2 H20 <--> 4[Au(S2O3)2]3- + 4 OH-

Tetrathionate formation.
2 S2O32- + 1/2 O2 + H2O --> S4O62- + 4OH-

Tri-Thionate formation.
_(3 S4O6 +5/2 O2 + H2O --> 4S2O3 + 4H+)_ I have no idea where you got this equation, but the sulfur-degrading works diffrent from tatra to tri and thio.

Sulfite formation.
S2O32- + O2 + 2 H2O --> 2 SO42- + 4 H+

Ammonium back to ammonia.
NH4+ + OH- --> NH3 (aq) + H2O --> NH3(g) + H2O


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## niteliteone (Feb 26, 2014)

Geo said:


> niteliteone said:
> 
> 
> > Geo,
> ...


I think it would have been fitting :lol: 
It completely slipped my mind (what little is left) of what process was being used here.


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## nh6886 (Mar 17, 2014)

Geo,

First I wanted to say thanks to you and all those who have contributed, and those pins look fantastic, congratulations!
I wanted to mention that I get most of my silver from used ammonium thiosulfate (fix) after 30,000 square inches of industrial radiography film has been processed in it. I recover the silver by using Manuel's Sodium Sulfide method which drops the the silver as Ag2S and leaves the "fix" ready to do more work. I have not reused it to process film but it works great to strip the silver from green film (unexposed) without removing the gelatin. Which for me means No sodium hydroxide, no oxalic acid, and no incineration is needed when I recover the silver.
I have completely saturated this solution to the point where it appeared not pick up anymore silver and it was stable for a couple of days until I dropped with Sodium Sulfide. I hope that's stable is the right word but in any case it didn't drop any visible silver from the solution. I have reused some of this solution five times so far with no visible or performance change. 
I don't know if this helps but I thought I would share what I've experienced incase it does. 
I can post a PDF of the Fix MSDS (there is a part A &B) from AGFA if you think it's of value.

All the Best,
John


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## Geo (Mar 20, 2014)

John, any information would be useful, if not to me personally, then maybe the next person trying this.


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## Loito (Mar 21, 2014)

Hallo Geo,

are there any new informations/findings/experiments about your leaching. Have you already tried to recover the leached gold? I am curious about that


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## Geo (Mar 21, 2014)

I apologize about leaving this open ended. Some circumstances has developed that has put my "hobby" on hold for right now. There was an accidental shooting on my property. Even though no one was seriously injured (unless you consider getting shot in the leg serious), the city code enforcement officer has an issue with me. The road I live on is divided. One side (my side) is city and across the street is county. The code enforcement officer, I think I'll just call him Mr. Pencilneck, told me he wanted to make an example out of my property. No buckets, nothing that will catch rain, no scrap, no boards, no loose lumber and both my sheds have to go because they are in a "dilapidated condition" and are not city code compliant. I must remove all the items on his list in 30 days or a warrant will be issued for my arrest and the city will clean it up and i have to stay in jail until the cleanup is paid for. 

Some of you already know some of this, but please dont be concerned, I've dealt with his kind before. I've rented a storage unit for the time being to hold all my boards, buckets and barrels. After the list is completed and he signs off on the clean up, im bringing it all back.  I bought a metal shed from Lowe's and will wait until he's satisfied to put it up. If i have to, I'll build a privacy fence that cant be seen over. Wonder what Mr. Pencilneck will find to mess with me about next time.


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## goldenchild (Mar 21, 2014)

Geo said:


> I apologize about leaving this open ended. Some circumstances has developed that has put my "hobby" on hold for right now. There was an accidental shooting on my property. Even though no one was seriously injured (unless you consider getting shot in the leg serious), the city code enforcement officer has an issue with me. The road I live on is divided. One side (my side) is city and across the street is county. The code enforcement officer, I think I'll just call him Mr. Pencilneck, told me he wanted to make an example out of my property. No buckets, nothing that will catch rain, no scrap, no boards, no loose lumber and both my sheds have to go because they are in a "dilapidated condition" and are not city code compliant. I must remove all the items on his list in 30 days or a warrant will be issued for my arrest and the city will clean it up and i have to stay in jail until the cleanup is paid for.
> 
> Some of you already know some of this, but please dont be concerned, I've dealt with his kind before. I've rented a storage unit for the time being to hold all my boards, buckets and barrels. After the list is completed and he signs off on the clean up, im bringing it all back.  I bought a metal shed from Lowe's and will wait until he's satisfied to put it up. If i have to, I'll build a privacy fence that cant be seen over. Wonder what Mr. Pencilneck will find to mess with me about next time.



Geo,

That is ridiculous. How can they tell you what you can and can't have on the property? I would fight it.


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## Geo (Mar 21, 2014)

Thanks Mario, I've had to deal with him before. Back when I got the first couple tons of the equipment these boards are out of, he came out on a "suspected meth lab" because of all the chemicals in plain sight. He said that he did't have a problem with that (at the time) but found a list of city ordinance violations. It cost me over $6000 to bring all of it up to code. I believe he is a friend of a couple of people who live on my road that would be pleased if I could be made to vacate. When I had completed all the things he had on his list, instead of being pleased with the results, it seamed to have upset him somewhat. I may look like I'm homeless but that doesn't mean that I'm without resources. I truly feel the he was expecting me to pack up and leave. This last incident was just an excuse for him to come back here and try again. This time he's going for my extra income thinking it will make a difference. I just want to complete the cleanup on his list and be done with it (until next time). 

There are people that support me in my neighborhood. There is one fellow (church deacon, retired city councilman) that wants Mr. Pencilneck's name. I ask him if he was planning on speaking for me and he said "no, I'm going up there and tell him to stop harassing you if he knows whats good for him". I may give him the man's name but that's against my principles. I really don't care too much for seeking retribution. I'm sure that Mr. Erney could cause the man some problems of his own and it's very tempting. I would only do that if he is really doing this out of malice and purely in self defense.


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## butcher (Mar 22, 2014)

Geo, I am sorry you are having this kind of trouble, But I am sure you can handle it. But still it is a shame you should have to. I always figured what goes around comes back around, and they will most like get their own due sooner or later.


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## waltao (May 22, 2014)

Hi, I'm writing for a while on this forum that I think the best.
I apologize for my English but I do not know I rely on automatic translator google.
Long story short, I did some tests using sodium thiosulfate, and I think I have good results.
Serves sodium thiosulfate, copper sulfate, ammonia and a good meter ph.

In this picture the connector is placed at the center as a reference to show the before and after.
The connector on the left has been soaked for longer hours than the right (in fact there are still sees gold to remove).

Walter


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## Geo (May 22, 2014)

Very nice results Waltao. I found that the tiny amount of gold left on the connector pins I tried flaked off after a couple of weeks. The pins are still silver looking but now there are some tiny gold flakes in the container.


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## waltao (May 23, 2014)

It is in fact the result is promising.
I'm testing various combinations of solutions, but the most promising is that of this result.
And here I put the composition that gives me this result.
100cc water
6.25 grams of sodium thiosulfate to obtain 0.25 M (Mole)
1.2 grams of copper sulphate to have 48mM (milliMole)
2mL ammonia to obtain an initial pH of 10.34
room temperature
closed container
manual stirring occasionally
I do the test results of each 8/12 hours, so far I've got it all in 24/36 hours.
Now I do the test to see when the saturated solution by providing additional gold-plated components.
Here are pictures:


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## solar_plasma (May 23, 2014)

Good work!

Are any metals problematic, like tin?


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## waltao (May 23, 2014)

What I'm using, bought on ebay except ammonia found in shop


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## waltao (May 23, 2014)

Hello solar plasma, it is too early to tell but it seems not


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## solar_plasma (May 23, 2014)

By the way, you should get those plastic isolations out, there is gold inside the tube, too. Sometimes you can pull them out with pliers or you just cut the whole ting half over.


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## shmandi (Jun 3, 2014)

Hello waltao,
How is your process going? Have you maybe tried dropping gold out of solution?


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## goldenchild (Jun 3, 2014)

I tried waltao's ratios of reagents and this leach finally seemed to work for me on a small batch of material. So I dropped everything with sodium sulfide (stinks like hell). Where to go from there? I tried something and I hope it wasn't too terrible to do. I decanted the leach and added hcl to the black sponge. I had to give it a really hard boil and what was left behind was some black powder. I'm assuming the majority of the black sponge was copper and the remaining is the gold? I will have to see what I come up with tonight.


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## solar_plasma (Jun 3, 2014)

I think sulfide precipitation might not be the best way, but since you have it, now, gold (I) sulfide will decompose at 217°C and above to Au and SO2 (-> roasting). I think I read about other methods on the forum, I just can't find them right now. Maybe it was just about smelting silver sulfide, - can't remember.


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## goldenchild (Jun 3, 2014)

solar,

Which method do you recommend to ppt the gold after it is in the thio leach? As I understood it the sodium sulfide was used to drop ALL metals from solution and leave nothing behind. So in boiling the black sponge are you saying that the gold is now in solution? I did notice the solution is now a nice yellow color but testing came up negative with stannous. And again there is some black powder that never went into solution.


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## solar_plasma (Jun 3, 2014)

I am also still only researching all the posts about thiosulfate, but this might give you some hints for further searching: my choice would be zinc. 

When you added HCl to the gold sulfide you probably produced H2S (be careful with this - poison) and your gold was left back in elemental form. Nevertheless I would heat the solids to drive off any sulfur, before proceeding.


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## waltao (Jun 3, 2014)

Here I am .
Unfortunately I have no positive results at the time .
I finished the thiosulfate and I am waiting for more material , so do not do other tests for now.
This is a quick guide to what I did .
After removing all the connectors from the solution, I noticed a black deposit was formed in the bottom of the container (in theory should not be there , at least not so abundant , what is it? Certainly not gold , maybe copper).
I then added a bit of zinc powder to cement the gold and make it fall .
The next day I praised and I was left with a rich black goo .
Neither I took half and put into Hcl, in a short time there is nothing left .
Only the ' HCL had become a little yellow .
For the sake stannous test done , of course negative.
So I took the other half of mush I melted in a crucible by adding a pinch of saltpeter .
Result a black spot with no trace of gold in sight.
My considerations :
1 ) gold removed from the plating is too little to be noticed.
2 ) gold has not taken off for anything you are just blackened connectors .
3 ) What is the safe method to precipitate the gold?

However, as soon as I get the thiosulphate, I do a test with a quarter ounce of refined gold already so I'll know for sure if that is processed and there are no other interfering metals .
For the record I also tried to concrete with steel wool , but nothing has changed.


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## solar_plasma (Jun 3, 2014)

...or maybe it just plated back.

Did you control pH and maybe ORP?


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## waltao (Jun 4, 2014)

the pH was under control.
Excuse my profound ignorance on the subject but what exactly does it mean, and what is the 'acronym ORP?


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## g_axelsson (Jun 4, 2014)

ORP = Oxidation Reduction Potential (http://en.wikipedia.org/wiki/Oxidation_reduction_potential)

Göran


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## waltao (Jun 4, 2014)

We thank you, however I also had done some research and I found this as well as make an instrument to measure the ORP, it is only a millivolt meter the problem will be the salt bridge and the platinum wire
Walter


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## solar_plasma (Jun 4, 2014)

you can buy those electrodes cheaply on ebay, I think I paid around 10€ - can't say how exact it is....probably better than nothing


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## solar_plasma (Dec 3, 2014)

goldenchild said:


> solar,
> 
> Which method do you recommend to ppt the gold after it is in the thio leach? As I understood it the sodium sulfide was used to drop ALL metals from solution and leave nothing behind. So in boiling the black sponge are you saying that the gold is now in solution? I did notice the solution is now a nice yellow color but testing came up negative with stannous. And again there is some black powder that never went into solution.



Maybe, I stay corrected (mostly page 4): http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=44&t=7938&start=60
sodium sulfide for precipitation - one member wrote, he tried all possible precipitants described in the literature and sodium sulfide worked best
sodium sulfite against the rotten eggs odor of H2S and/or for regeneration

maybe more important notes, I thought page 2 is interesting, but confusing too): http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=12284&start=20
Dr.Poe states that iron wool or zinc powder are the best to cement the gold from this solution. Confusing.

wiki says both monovalent and trivalent gold sulfide is black-brown
the first link says sodium sulfide will "not precipitate all the other crap"
=I would assume the precipitate, that you got, to be gold sulfide

sulfides are normally roasted (though there are also threads about smelting silver sulfide) to remove the sulfur (evolves SO2), aren't they.. So, more reading is needed, but if I am right, after roasting it should be possible to dissolve the powder and test it.

(only some ideas for further reading and searching, not meant as a practical advice)


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## g_axelsson (Dec 3, 2014)

solar_plasma said:


> maybe more important notes, I thought page 2 is interesting, but confusing too): http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=12284&start=20
> Dr.Poe states that iron wool or zinc powder are the best to cement the gold from this solution. Confusing.


Warning! Poe turned out to be a charlatan and certainly not a doctor. Some things (a lot) he said was just garbage told in a way that he would look like a professional. He was later exposed and ported from the forum.

In my opinion the signature of Poe should have a warning attached to alert people of this.

Göran


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## solar_plasma (Mar 14, 2015)

I have found a nice text about thiosulfate leaching of cell phone boards. Most interesting: The conclusion in the end.

http://article.sapub.org/10.5923.j.ijmee.20120102.02.html#Sec5


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