# The Stock Pot



## kadriver (Sep 30, 2014)

I looked for a thread dedicated to the "Stock Pot" but could not find one. This important refining tool is talked about in many posts, but no centrally located thread or tutorial about what folks use as a stock pot or what goes into (and what should be kept out of) the stock pot.

I recently started refining material that contains trace amounts of platinum, palladium and other platinum group metals (PGMs). I was spending lots of time and energy trying to recover these trace amounts and realized that it was wasted effort. Instead of chasing after these trace amounts, it was pointed out to me by an experienced refiner (Harold_V), that adding these trace amounts to the stock pot makes way more sense.

The stock pot was a phantom to me, its function was not all that clear. I have been doing small-time refining for several years now and it just hit home how important the stock pot is - to any refiner at any level.

Having said all that, I now have some questions; where can the stock pot be stored? After adding a few SMB doses to my HDPE (high density polyethylene) 5 gallon bucket that I now call my "stock pot", it stinks to high heaven and emits gases as it reacts with the scrap steel I have added to it.

I thought about getting a large plastic garbage can with a tight fitting lid, cutting some holes in the side so air can get in and aid evaporation. Then sitting the stock pot inside this garbage can and covering it with the tight fitting lid to keep the rain out of it. Then just sitting the whole thing outside in my back yard.

Also, I had some silver/copper nitrate solution. I added just enough HCl to precipitate out the silver chloride. I did a stannous test on the left over solution and there was traces of platinum in the solution - but all the silver had been removed. Can I add this copper nitrate solution that contains traces of platinum to my stock pot? I saved it out until I am sure that it is ok.

Harold_V has said that some silver present in the stock pot that contains gold and PGMs is ok (even a good thing) because it acts as a collector of other metals when the stock pot is processed to recover the previous metals. BUT, this was with the condition that the metals in the stock pot were going to be recovered in a furnace, where the silver would be rendered to metal from the silver chloride by the intense heat of the furnace and serve as a collector of the other precious metals (I hope I understood this correctly Harold).

How about those who do not have a furnace and plan to recover the PMs via wet chemical processes? Should silver chloride be avoided in the stock, in this case (wet chemical recovery)?

Thanks to all who respond to these and other questions that may present themselves.

kadriver


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## Harold_V (Oct 1, 2014)

kadriver said:


> I thought about getting a large plastic garbage can with a tight fitting lid, cutting some holes in the side so air can get in and aid evaporation. Then sitting the stock pot inside this garbage can and covering it with the tight fitting lid to keep the rain out of it. Then just sitting the whole thing outside in my back yard.


The stock pot has the potential to be a fire hazard, so capping it isn't in the cards. A considerable amount of hydrogen is released, especially when there is excessive acid in the solutions. 

My stock pot was small---just a 5 quart ice cream bucket, which was processed when it had outlived its useful life. The interior gets coated with values, so incinerating and processing was to advantage. 

My stock pot was located just below the opening of my fume hood, which was rarely not in operation. The noxious gasses that emanate were discharged, along with the generated hydrogen. Size appeared to be adequate, as I operated with concentrated solutions, so my volume was relatively small. However, I also kept my stock pot heavily charged with scrap steel, so there was a generous amount of surface area, cementing values quickly. I decanted the stock pot daily, but to a secondary container, which was allowed to settle well before the solution was discarded. Make absolutely sure you don't discard anything in the way of solids. 

On rare occasion, I'd experience ignition of the hydrogen. Because it was never allowed to accumulate, there was a flash (very pale in color and slight in volume) and it was extinguished. If you allow it to accumulate, that may not be the case, and, indeed, you can destroy your refining area. Make sure you are ventilating well when your stock pot is active. 



> Also, I had some silver/copper nitrate solution. I added just enough HCl to precipitate out the silver chloride. I did a stannous test on the left over solution and there was traces of platinum in the solution - but all the silver had been removed. Can I add this copper nitrate solution that contains traces of platinum to my stock pot? I saved it out until I am sure that it is ok.


That would have been my routine, but keep in mind, I did my final recovery in the furnace. If you find you have traces of values present, and you intend to recover the values chemically, instead of recovering the silver via the chloride method, you might consider cementing. Given a long enough exposure to the copper, all traces of values will be cemented, so you'd allow the traces of values to accumulate in your silver instead of the stock pot. Be advised, silver will come down first, so you'll likely have to wait longer than you might otherwise have waited. 



> Harold_V has said that some silver present in the stock pot that contains gold and PGMs is ok (even a good thing) because it acts as a collector of other metals when the stock pot is processed to recover the previous metals. BUT, this was with the condition that the metals in the stock pot were going to be recovered in a furnace, where the silver would be rendered to metal from the silver chloride by the intense heat of the furnace and serve as a collector of the other precious metals (I hope I understood this correctly Harold).


Close, but not quite right. Heating silver chloride alone won't reduce to elemental silver. Adding soda ash will. My flux recipe had a generous amount of soda ash, so I got a respectable recovery. How much that may have been lost to the atmosphere I can not say, but the resulting slag assayed too low in all values to be worthy of further processing. 



> How about those who do not have a furnace and plan to recover the PMs via wet chemical processes? Should silver chloride be avoided in the stock, in this case (wet chemical recovery)?


Depends on how you'd do your recovery. Even silver chloride is likely to be reduced to elemental silver in the stock pot---but you now have a gathering of materials that would require dissolution in nitric, to recover the silver. That may or may not be to your advantage, as the resulting solutions may not lend themselves well to filtration. That's one of the reasons I chose to make my recovery by furnace, where undesirable substances would be eliminated. My logic appears to have worked well, as I had no issues with the refining. 

Harold


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## g_axelsson (Oct 1, 2014)

You should read Hoke chapter 13 about the stock pot. (page 143-155)

Here are some more threads about the stock pot:
* Harold's five quart ice cream bucket
* Harold, sending iron filing to the stock pot
* Harold, filtering and incinerating the cemented metals
* Harold, emptying the stock pot
* Harold, 20 year stock pot savings plan
* Harold, hydrogen from the stock pot ignites
* Harold, short introduction

We all know who has written most about the stock pot on this forum. Thanks Harold!

Göran


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## kadriver (Oct 1, 2014)

Excellent, now this is all in one spot! I have read Hoke's chapter on the stock pot. She says to use a "large crock of good quality stoneware" (Hoke page 143). Does anyone actually use a stoneware crock as a stock pot?

I bought this one at a yard sale.

I have seen the light and now realize how important the stock pot is. But it took over 4 years of refining experience to realize this! I would just like other folks who are new to refining see the importance sooner in their refining experience.

Having all the info in one thread will help, I hope.

kadriver


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## kadriver (Oct 1, 2014)

By the way, for anyone who wants a nice hard bound copy of Hoke's book you can go to:

http://www.gesswein.com

Type in "Hoke" in the search block on the gesswein site and the book "Refining Precious Metal Wastes" will be displayed. It can be ordered from Gesswein for about $55 plus shipping.

Here is my copy. I downloaded the PDF from our user Palladium, find any post by him and you will find the PDF download inside his post.

I printed that PDF out on my printer and put the pages in document protectors and keep that at my shop for reference.

I keep the book with me at all times and when I have to wait somewhere I get it out and read.


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## kadriver (Oct 1, 2014)

Harold, what material was the 5 quart ice cream bucket made of?

It would be difficult to incinerate a 5 gallon HDPE bucket, but adding hot AR to the bucket to recover the values might work.

kadriver


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## FrugalRefiner (Oct 1, 2014)

For those who would like to print out their own copy, I created a printer friendly copy of the book that will print out on half the number of pieces of paper. I also created a screen readable copy. Both copies include a lot of corrections to the original digital copy in Palladium's signature line, as well as improved pictures and an introduction with updated safety information. I know they weren't available when you started, but copies of both are available in my signature line.

Dave


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## Harold_V (Oct 1, 2014)

kadriver said:


> Harold, what material was the 5 quart ice cream bucket made of?
> 
> It would be difficult to incinerate a 5 gallon HDPE bucket, but adding hot AR to the bucket to recover the values might work.
> 
> kadriver


The typical ice cream bucket. Don't happen to have one at my disposal right now, so I'm not certain of its makeup. What ever it may be, it reduces to oil when heated, then burns (with a vengeance). A bit messy, and probably not the smartest thing to incinerate, but in all my years, I incinerated only a small handful of them, as they last a long time. By the time it was necessary, the interior was deep black, the result of values and carbon (from the scrap steel) being firmly attached (that's the reason I NEVER used plastic to precipitate). 

You most likely would enjoy success of some description stripping the values with acid (AR). The only problem is that there's a lot of surface area to cover, and platinum, if present, would be slow to dissolve. Incinerating such a large item, made all the worse because they have a thicker cross section and heavily reinforced upper section and base as compared to an ice cream bucket, didn't appeal to me. For that reason, I never even considered using a five gallon bucket, nor did I have need. By keeping your solutions in check (volume), and keeping a good supply of scrap steel in the stock pot, there is no need, as the five quart container was more than adequate in keeping up with my discharge stream. Do keep in mind, I refined on a regular basis, so my stock pot was in use constantly. 

Harold


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## kadriver (Oct 1, 2014)

I'm going to find me a 5 quart ice cream bucket and use just like you said. I'll bet the local Dairy Queen will have one.


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## Shark (Oct 1, 2014)

This is a 5 quart ice cream bucket that I use. It is made by Berry Plastics, but I haven't took the time yet to see if their web sight has an MSDS sheet on it. I just thought it would be a good sight picture of the metals attaching themselves to the plastic, and validates what Harold is saying about not precipitating in plastic for the newer people. It is sitting on top of a blue 5 gallon bucket. The light spots are where steel was laying from the last use.


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## Barren Realms 007 (Oct 1, 2014)

Just be careful on the length of time that you use them because they will become brittle over a period of time especially if left outside where the UV rays have access to it.


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## Palladium (Oct 1, 2014)

The most important thing I have learned from Harold besides his washing method is the stock pot. It my retirement plan for life also. The reason I refine myself is not for the profit, but for the values as an investment! As a newbie it is the last line of defense to catch those values that you're losing because your technique is not yet perfected. I started by using steel, but I was running large volumes of feedstock so the amount of solids I was producing was growing when I used steel to cement the trace values along with all the other metals on the reactivity list. I switched to using copper dust which I reclaimed from the cementing stage after the stock pot and before disposal. First I place my solution in a five gallon bucket with a liner that is easy to incinerate http://www.usplastic.com/catalog/item.aspx?sku=10031&gclid=Cj0KEQjwzK6hBRCbzLz_r_f-3tkBEiQA-zyWsIZT_FojrMwB7cXLDIPOLdSlVZavHHQc6T1Bt3fdMoQaAoHU8P8HAQ You can get them at Lowes. Then I add cemented copper in small amounts so I can always see that when I decant the bucket there is always copper still in the bottom of the bucket which lets me know I'm good to go. Too much copper just throwed into the bucket will solidify into a chuck of hard materials. I then add an aquarium bubblier like in the ap process to keep the solution agitated and after a couple of days I decant the solution and move it to another bucket. This is where I add steel and drop the copper that I will use for the stock pot cementing and when the process is done then the solution is ready for disposal in the next step. I keep separate buckets for gold and silver solutions and I don't mix them.


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## Smack (Oct 1, 2014)

Plastic wasn't the norm back in Hoke's day, if she wrote the book today some of the materials she used and describes would vary because of the plastic revolution if you will.


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## Palladium (Oct 1, 2014)

With the waste processing streams I generate the stock pot has paid for itself a 1,000 times over. I run gold filled lots in 10-15 lb increments 5 days a week for some clients. The amount of silver that comes from the recover of gold filled can start to add up. I use to salt the nitric and just recover the chlorides, but that way is a pain in the blank and you can lose some pd that way. Now it's strictly cementing and melt then straight to the cell. On the flip side you have heard me gripe about how much I hate silver! Well ....... it kind of grows on you.  I've got a client who melts his gold filled over sterling into a bar and he sends it to me to put through the cell. I'm getting 10% and every time I run a large batch I can count on that percentage of gold being there. The agreement with gold filled is no silver return and the deal with silver is no residual gold returns. I tell my clients that up front and unless there is special circumstance that's the way it goes. I'm not chasing those traces through all those solutions and steps. I dare to say that it accounts for a significant amount of my profit in metals.


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## Pantherlikher (Oct 1, 2014)

kadriver
Excellent idea with stock pot systems in 1 place.

That crock you have pictured is worth a lot so be nice to it.

Instead of the plastic bucket, I use 2 crock pots as in slow cookers. Cheap at yard sales and thrifts.
The first 1 has copper in it at all times until I run out of things to extract PMs from.

The Second crock has steel in it to drop copper for pot 1.

After that, I have a 5 gal. bucket as it sits the longest. I let it evaporate as long as I can while raising the pH. 
Last year, I removed about half a bucket and raised the pH enough to dispose of.

Time and my pile of scrap have not allowed me to do much of anything this summer....Bummer there.


I keep the crock pots in the outgoing breeze in my shed so any fumes are carried out as fast as possible. 
For now, I only use HCl + bleach, or AP so there is no mix of fluids to be concerned about.

I think it good though to keep different fluids from different processes with PMs separate. Unless of course you have different PMs such as filled and what not. If you have metals separated, why combine them and make more work?

The slow cooker crocks also have a built in heater so you can heat to speed evaporation.
They come in different sizes so you can find 1 that works for your loads.

In the perfect world, we would be collecting and refining from all kinds of material and for all kinds of PMs.
These can be separated into different PM content, using different Acids and thus have different pots with copper to keep the different PMs as separated as possible. After the copper pot, almost everything can go into the pot with steel to drop copper and then further for disposal.

B.S.
Anyone else have anything to add? Or to correct me, please


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## kadriver (Oct 1, 2014)

Palladium, thank you for sharing these insights. This is the second time (first from Harold, now from you) I have heard to cement the silver on copper to get the palladium and platinum, if any.

I found some angle iron and cut it up into smaller pieces, then pickled it in HCl to remove oxidation. I then put it into my stock pot.

Also, I am working on another batch of polishing sweeps and had a filter to burn. I cleared my work area and put down news paper. Then I cut open a white plastic trash bag. I set the filter on the opened-up bag and carefully removed the steel grate and staples.

The steel grate looked perfect for a large surface area for my stock pot. It had some glue and other junk so I incinerated it before putting it into the stock pot. I still have a 5 gal HDPE bucket for now until I can find the ice cream bucket. Having this stock pot is like having a new toy in my shop. I had solutions in containers all over the place and didn't quite know what to do with them. Now they go into my stock pot.


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## Palladium (Oct 1, 2014)

I use steel turnings I get from the scrap yard for 10 cents a lb and heat in a $10 yard sale toaster oven to drive off any oils. Remember surface area and cross diagonal area (thickness) will determine the reaction kinetics of the solution on the surface of either the copper or the steel = reaction time for complete cementation. That's why I like the air bubbler! Before I used turnings I used scrap cut off pieces of steel roofing that you can find thrown away just about anywhere if you look or know somebody. I've even used hollow metal wall studs for framing sheet rock walls that get thrown away by the wheelbarrow loads. They are thin and have a large surface area and get completely eaten up.


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## kadriver (Oct 2, 2014)

I had a copper nitrate solution that was devoid of any silver. I removed the silver with HCl to form silver chloride then allowed the silver chloride to settle completely. I decanted the blue solution and tested with stannous chloride. There are traces of Pt in the copper nitrate. If I add this to my stock pot that is full of iron and steel right now then the copper will cement out on the steel and the PMs will then cement out on the copper. Is this the correct line of thought with respect to adding copper nitrate solutions to the stock pot?

I can see the importance of not allowing iron filings or cemented copper to pile up excessively to form the "hard lump" referred to earlier. I added only a spoon full of iron filings to my stock pot and they were nearly completely consumed when I checked the bottom by tilting the bucket.

My 5 gallon bucket is about half full right now. I put all the solutions into the bucket so I could start using the glassware again. I had solutions in beakers everywhere. When the cementing is done and the solution clears I will decant and set aside to ensure nothing settles out then commit the clear solution to waste treatment - after I test with stannous.

kadriver


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## kadriver (Oct 2, 2014)

FrugalRefiner said:


> For those who would like to print out their own copy, I created a printer friendly copy of the book that will print out on half the number of pieces of paper. I also created a screen readable copy. Both copies include a lot of corrections to the original digital copy in Palladium's signature line, as well as improved pictures and an introduction with updated safety information. I know they weren't available when you started, but copies of both are available in my signature line.
> 
> 
> Dave



Frugal, I completely overlooked this. These links are absolutely wonderful, (Calm Morrison Hoke was kind of easy on the eyes too). That's the first I have ever seen of her that I can remember. She never knew how much she contributed to the success of the contemporary refiner!

If I remember correctly the link to Hoke in Palladium's reference was missing a page, I think it was page 177. I had to check the book out at our public library and make a copy of this missing page so I would have a complete copy of the book for reference at my shop.

kadriver


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## FrugalRefiner (Oct 2, 2014)

kadriver said:


> I had a copper nitrate solution that was devoid of any silver. I removed the silver with HCl to form silver chloride then allowed the silver chloride to settle completely. I decanted the blue solution and tested with stannous chloride. There are traces of Pt in the copper nitrate. If I add this to my stock pot that is full of iron and steel right now then the copper will cement out on the steel and the PMs will then cement out on the copper. Is this the correct line of thought with respect to adding copper nitrate solutions to the stock pot?


It's not that copper will cement on iron and _then_ PMs will cement out on the copper. Every metal below iron in reactivity will cement out on the iron. If all you had left in solution were PMs, with no copper at all, the PMs would still cement out on the iron. 

Harold cemented everything with iron because he processed all the cement through his furnace. The iron works well because it's much more reactive than the PMs. Many forum members have adopted a two step approach, first cementing out their PMs with copper, then moving the solution to a second container to cement out the copper. For those without a furnace, the advantage is that only PMs (and mercury, if present) will cement out on the copper. This residue is easier to process wet because there are fewer contaminants. Then, to remove the remaining heavy metals to make the waste solution less toxic, it is cemented on iron. It must be remembered that iron will cement not just copper, but any less reactive metal in solution, e.g., cadmium, cobalt, nickel, tin, and lead. So if you go directly to iron, you can have a mix of all of these metals (assuming any of them were in your solutions). In the furnace, most of the base metals will be volatilized or oxidized and will end up in the slag. If the residue is processed wet, you have to deal with eliminating the base metals.



> If I remember correctly the link to Hoke in Palladium's reference was missing a page, I think it was page 177. I had to check the book out at our public library and make a copy of this missing page so I would have a complete copy of the book for reference at my shop.


The original copy was missing a full page as you mentioned, but also another partial page. There were also many typographical errors introduced when the book was digitized. The word iridium was a problem for the OCR software, which interpreted the "ri" as an "n", so if you read the original digital copy, you'll see many incorrect instances of "indium" instead of "iridium". I corrected as many errors as I could find by comparing the hardcopy I bought from Gesswein and the copy of the original 1940 printing my wife got through an inter-library loan.

Dave


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## 4metals (Oct 2, 2014)

> I then add an aquarium bubbler like in the ap process to keep the solution agitated and after a couple of days I decant the solution and move it to another bucket. This is where I add steel and drop the copper that I will use for the stock pot cementing and when the process is done then the solution is ready for disposal in the next step.



This is essentially the process used for waste treatment which has been discussed on the forum. With the exception that the pH need be increased to 2.5 before adding the iron. 

I have never used a stock pot per se. If I processed a lot for gold and the lot had payable platinum I would always zinc the entire lot, add HCl to get rid of the excess zinc, roast the sludge and process the sludge accordingly. This saved me the time of evaporating the solution down as I was able to keep the volume of the solution used to digest sludges down to a minimum so the Pt (and Pd) was concentrated enough to drop easily. Another benefit of this procedure is the metals you recover from the sludges are finely divided and will dissolve in HCl and sodium chlorate so there is no need to get rid of any excess nitric. The waste from this process went into the standard flow for aqua regia waste.

All solutions that had been precipitated were placed into a cementation tank and all waste acids were cemented with copper. This essentially was my stock pot. The solution from there went to the next tank for the pH increase and the iron to recover the copper. The copper recovered was dried and melted and cast in an anode mold to be used in the cementation tank. 

The waste was now essentially ferric chloride so it was easy to drop out the iron as a hydroxide and neutralize the waste for discharge. The classic metal hydroxide method involves raising to a pH of 10 to drop all of the metals as hydroxides and then it has to come back down (by acid additions) to neutral for discharge. This method eliminates that step because the iron comes out around pH 3 to 3.5 and after filtration to remove the iron cake the solution only needs additional alkaline to get to discharge pH. Back when I did this the waste met discharge standards, today it would likely need some carbon polishing. Often refiners use this process to clean up their waste and have the "process water" removed for a fraction of the cost it would cost for the waste acid removal and it is removed as a non-hazardous waste.


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## kadriver (Oct 3, 2014)

I got a smaller bucket and began using this as #1 of 2 stock pots. In the smaller #1 I will use copper to cement out trace amounts of gold and PGMs. Then I'll transfer the resulting copper solution to the larger iron stock pot #2 to cement copper onto iron for use in stock pot number one.

I hope I got this right. I used bits and pieces of copper wire instead of powdered copper.

kadriver


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## MarcoP (Oct 3, 2014)

So raise PH to 2-2.5 before adding scrap iron and then when at 3-3.5 the iron will come out by it self?
Sure other metals hydroxides and carbonates will drop at 9, but still great to know (unless I misunderstood).


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## butcher (Oct 3, 2014)

Here is one chart showing the pH range some metals precipitate around.
http://hoffland.net/treatment-processes-chemistry-2/hydroxide-precipitation/

Note: Some metals are amphoteric and will precipitate in a basic solution and dissolve again in an excess of that same basic compound.
http://www.docbrown.info/page07/appendixtrans12.htm

http://cpe.njit.edu/dlnotes/CHE685/Cls06-2.pdf

more for further research,
https://www.google.com/search?newwindow=1&site=&source=hp&q=metal+hydroxide+precipitation+chart&oq=metal+hydroxide+precipitation+chart&gs_l=hp.13..0i22i30.2331.18279.0.20590.36.30.0.6.6.0.314.3477.16j12j1j1.30.0....0...1c.1.54.hp..1.35.3380.0.LXh8Xi7d-iw


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## MarcoP (Oct 3, 2014)

That answers many questions, new questions that would eventually come up and I even found unexpected information! I'm sure one day I would have searched about it, but you Sir just made my day and gave new keywords to look up for.
Thank you butcher!


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## kurtak (Oct 5, 2014)

1 gallon & 2 gallon cookie jars from Walmart make great stock pots - unlike plastic buckets they don't become impregnated with metals you are trying to recover (as Harold talked about) metals may stick to the walls but you can just wipe the walls down with a paper towel & add the paper towel to your filter burn bucket for later recovery when incinerating your filters

I have been using them since I started doing this & really like them for this purpose

Kurt


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## 4metals (Oct 5, 2014)

Kurt,

The stock pots are nice but I really like the silver cell! No refiner's workbench would be complete without a little gem like that!

What volume does it hold and how many amps do you pull?


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## Shark (Oct 5, 2014)

> 1 gallon & 2 gallon cookie jars from Walmart make great stock pots - unlike plastic buckets they don't become impregnated with metals you are trying to recover (as Harold talked about) metals may stick to the walls but you can just wipe the walls down with a paper towel & add the paper towel to your filter burn bucket for later recovery when incinerating your filters
> 
> I have been using them since I started doing this & really like them for this purpose
> 
> Kurt



I just had one of those real "DUH" moments. I have no idea why I haven't already thought of it, as I have one of those cookie jars needing a good use.


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## GotTheBug (Oct 5, 2014)

I use those wally world jars a lot also, and learned a valuable (or shall I say values lost) lesson about using them with any heat....


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## kurtak (Oct 6, 2014)

4metals said:


> Kurt,
> 
> The stock pots are nice but I really like the silver cell! No refiner's workbench would be complete without a little gem like that!
> 
> What volume does it hold and how many amps do you pull?



I'm running a BK Precision 10 volt/10 amp linier power supply - the cell takes 4 liters electrolyte to the bottom of the anode basket & the anode basket holds 3 two pound anode bars (so 6 lb silver) & it can pull the full 10 amps continual for as long as I need (I can "set" the current limit so I actually set it at 9.8 which it will pull once the cell is about half full of crystals)

It was kind of a spendy power supply (about $500) but the first one I bought was one of those cheep made in China $100 ones from ebay & I burned it up in no time - this one is near indestructible - well worth the money

At the time I bought it 10 amps was enough but I am getting to a point where I run enough silver that I am considering getting a 20 amp & maybe even a 30 amp - but they run 2 to 3 times the money & with silver down so low right now it's hard to justify - so for right now I will just keep running this one - it's built to take the heat of running non-stop for days

Kurt


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## kurtak (Oct 6, 2014)

GotTheBug said:


> I use those wally world jars a lot also, and learned a valuable (or shall I say values lost) lesson about using them with any heat....



They will actually take a fair amount of heat you just have to be "careful" you don't thermal "shock" them or apply direct heat (put them directly on a hot plate).

I have done "a lot" of silver chloride conversion in them (& they get quite hot when you add the NaOH) as well as using them for silver cementing & stockpot cementing & in 4 years have "never" had one brake --- I "always" put them in a shallow plastic tote/bin for secondary containment just in case & that was only needed one time when I added too much NaOH too fast to a AgCl conversion & had a boil over - never broke one though.

So I am kind of curious as to what you did to have one break ? 

Kurt


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## Harold_V (Oct 6, 2014)

GotTheBug said:


> I use those wally world jars a lot also, and learned a valuable (or shall I say values lost) lesson about using them with any heat....


Or with heavy pieces of scrap metal. The jars are nice, but subject to breakage. That's the reason I used an ice cream bucket. Never had one fail in all my years of refining, but I can't count the number of broken glass vessels I experienced. 

Harold


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## Palladium (Oct 6, 2014)

Harold_V said:


> GotTheBug said:
> 
> 
> > I use those wally world jars a lot also, and learned a valuable (or shall I say values lost) lesson about using them with any heat....
> ...



+ 1

The only thing I really use glass for is the final refining of gold. Everything else is stainless and plastic. 
I'm the paranoid type! :mrgreen:


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## rickbb (Oct 6, 2014)

I'm not the paranoid type, just clumsy. Glass just doesn't last long around me. sigh.


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## kadriver (Mar 2, 2015)

Palladium said:


> This is where I add steel and drop the copper that I will use for the stock pot cementing and when the process is done then the solution is ready for disposal in the next step. I keep separate buckets for gold and silver solutions and I don't mix them.



Palladium,

I am getting quite a buildup of copper in my 2nd bucket that is charged with iron.

Do you just add the bits of copper back into your stock pots, or do you melt into ingots first?

Thanks, kadriver


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## Palladium (Mar 2, 2015)

I guess you could do both, but to me melting only takes away surface area and cost extra time and money. I just add the copper powder to my waste disposal bucket after removing it from my cementing bucket without washing it or anything. Waste bucket to waste bucket is all I do. If you just cement without air agitation then the powder will give you more reaction surface than a bar does. If you use a bar I would use air agitation. Don't fill the whole bottom of the bucket with copper or it will crust up into a clump. Use moderate amounts and every time you empty your bucket check to see you have excess copper in the bottom. Using copper in your stock pot it will not consume near as much copper to drop the precious metals as with iron because iron will replace everything above it where as copper won't. The end result should be a cleaner stock pot which is easier to process.


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## jason_recliner (Mar 2, 2015)

This is something that has been perplexing me this week, as I am _still_ tidying up my first mistakes, a year on.

I have a small jar containing a 1kg solid block of copper, in which potentially gold bearing (amongst other things) solution sits for a week or three. I guess that's my stock pot. Then I gently syringe off the almost black solution into a 1l waste jar containing iron. Originally that iron was sandblasting grit but it reacts too quickly, causing foam and heat. Instead, now I drop in a dozen or so rusty nails.

So now I have a slowly clearing pale green/blue solution in the waste jar with a good inch or so of copper precipitate.

If I understand correctly, you're saying that you use this powder from waste bucket back into the stock pot. I am having trouble comprehending the method of reusing copper for the stock pot in powdered form.
The idea of the stock pot, as I understand it, is to recover gold powder. If I add copper powder from the waste jar to the stock pot, gold will precipitate but that gold still needs to be separated from the copper - all over again. That sounds like a circular flow to me. If it were melted into a bar, for which I don't yet have the facilities anyway, it would be much cleaner, though slower?

Also, a minor point, how would I know when it's consumed? I can't just lift and check it like a solid bar.


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## kadriver (Mar 3, 2015)

jason_recliner said:


> If I understand correctly, you're saying that you use this powder from waste bucket back into the stock pot. I am having trouble comprehending the method of reusing copper for the stock pot in powdered form.
> The idea of the stock pot, as I understand it, is to recover gold powder. If I add copper powder from the waste jar to the stock pot, gold will precipitate but that gold still needs to be separated from the copper - all over again. That sounds like a circular flow to me. If it were melted into a bar, for which I don't yet have the facilities anyway, it would be much cleaner, though slower?
> 
> Also, a minor point, how would I know when it's consumed? I can't just lift and check it like a solid bar.




I am just getting a handle on stock pot usage and terminology. Palladium says he uses TWO stock pots; one for silver wastes, and another for gold wastes. In his writing above, he transfers the copper from waste bucket to waste bucket. I have one stock pot that has lots of copper in it. I have a second bucket that has lots of iron in it (I am using angle iron, eight 12 inch pieces) and then a waste treatment bucket used to precipitate out the dissolved iron with sodium hydroxide (50LB bucket from Duda Diesel for $100 deliver via ebay).

I have been adding my gold and silver wastes to my stock pot that is loaded with copper. But I am switching to two stock pots like Palladium, one for gold wastes and another for silver, both will contain copper. I don't use a bubbler yet, I give it a good stir several times a day, but I plan to start using one. When I feel comfortable to do so, I allow the stock pot to settle over night. I then siphon off the blue to blue green liquid (I use ferrous sulfate and SMB as gold precipitants so there is iron in solution in my stock pot) into the second bucket that contains lots of pieces of angle iron. I stir this bucket at the same rate as my stock pot. This bucket eats iron pretty fast and the copper is building up in it. After I feel comfortable, I siphon the liquid from the iron bucket into a waste treatment bucket and process this liquid with sodium hydroxide.

I guess I am a little confused by the terms "waste bucket to waste bucket". I envision this to mean that the copper cemented out in the bucket that contains iron is transferred BACK to the stock pot for use to cement out traces of gold and PGMs. This makes sense because the acidic solution in the stock pot will consume copper as it cements out the PMs relieving me from having to add valuable pure copper to the stock pot. The copper is used OVER AND OVER in this way.

Plus if I siphon off any PMs still in solution FROM my stock to my second bucket that is loaded with iron, the PMs will cement out and settle with the cemented copper as the angle iron goes into solution. These PMs will get placed BACK into the stock pot when I transfer the copper out of the angle iron bucket back to the stock pot.

This is how I understand the stock pot to function from where my knowledge is at this writing. Since I have picked up a jeweler as a customer I am seeing an increase in PGMs (although only in traces amounts) and my waste production has increased dramatically also.

As a side note, I am planning on waiting as long as possible before I try to refine the PMs in my stock pot. I am going for the Harold_V retirement plan.

A note to jason_recliner, if you look at what I have written you will see that the copper gets recycled so you don't have to continually add virgin pure copper to the stock pot. And you get a second chance to get any PMs that are (inadvertently, accidentally, ignorantly) siphoned out of the stock pot and into the bucket with iron in it.

If I am in error here then any guidance would be greatly appreciated.

kadriver aka sreetips


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## jason_recliner (Mar 3, 2015)

One distinction I would like to clarify is the term "waste", and it seems to be a sticking point of confusion with more people than just myself.
In my current understanding, waste is not the solution that goes into a stock pot, rather that which comes out of it.

Only solutions with values, or probable values, go into the stock pot.
The copper enriched solution that comes OUT of the stock pot, HCl washings after incineration (unless reused for other purposes), expired stannous chloride, et al. I consider these are waste. "Waste" is to ultimately have all metals removed (whether by Cu, Fe individually or by all metals simultaneously is not my point here) and the resulting clean salt water dumped.

Even then, there may be good reasons to put certain waste items into the stock pot. HCl washings for example, may help keep a nice low pH. But you would never include your old stannous chloride - for we all know tin in your gold is just evil. :twisted: 

So this was my comprehension of what Palladium does, as he mentioned "cementing bucket" and "waste disposal bucket". Therefore I believe "Waste bucket to waste bucket" just means "bucket to bucket".



> Palladium says he uses TWO stock pots; one for silver wastes, and another for gold wastes.


It makes good sense to have one for as many different items as you regularly process individually. I'm merely simplifying, to speak of one at a time.

For any given stock pot, adding copper powder would mean it's partially or wholly replaced by gold powder. You would have a Cu/Au powder mix. I guess this is still pretty easy to re-process, but you'd be having to redissolve the copper all over again as opposed to extracting only small amounts of non-values if you used busbar or ingot. On the other hand, ingots mean work and busbars mean expense.


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## MarcoP (Mar 3, 2015)

As a side note, why aren't you using calcium hydroxide for waste treatments? It's easy cheaper then sodium hydroxide and little easy to filter off. I can buy 25Kg locally at €3-€3.50.


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## kurtak (Mar 3, 2015)

MarcoP said:


> As a side note, why aren't you using calcium hydroxide for waste treatments? It's easy cheaper then sodium hydroxide and little easy to filter off. I can buy 25Kg locally at €3-€3.50.



Correct - calcium hydroxide (lime) is the better way to go for removing the iron after using iron to remove the metals below it in the reactive series - its cheaper & easier to filter - the down side is it takes longer to react & drop the iron out then NaOH --- if the solution is too dilute &/or temps too cool it can take a few days for calcium hydroxide to do its job - where as NaOH gets the job done in dilute solutions &/or cool temps.

So I use both - depending on conditions.

Kurt


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## kurtak (Mar 3, 2015)

Keven - Jason

Agitation is key to the success of cementing (ether "constant" stirring or bubbling) especially if there is a high concentration of PGMs.

I was having trouble with this awhile back with solutions with high levels of PGMs that I posted about & 4metals helped to clear the problem up in this thread :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=21218&hilit=cementing#p219231

My first couple post explain the problem then 4metals helps solve it - hope that helps you guys as well.

When you cement your copper (with iron) the more dilute the solution is & with bubbling agitation your copper will come down finer - then if you use the copper powder - in small additions  - to your stock pot - with constant stirring - it should improve your stock pot recovery without ending up with a lot of copper contamination.

Kurt


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## jason_recliner (Mar 3, 2015)

Thanks Kurt.
I've seen that thread before; it makes a bit more sense now, and different sense too.


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## FrugalRefiner (Mar 3, 2015)

I too use a two bucket stock pot system, with copper in the first and iron in the second. All of the precious metals are below copper in the reactivity series, so given enough time and agitation, they should all cement out completely in the copper bucket. When I move the solution to the iron bucket, the copper will cement out on the iron. 

I think it is important to remember that everything below iron will also cement out in this bucket, not just copper. This means you _could_ have a mix of copper, antimony, arsenic, bismuth, lead, tin, nickel, cobalt, cadmium, etc. if any of those metals are in your waste stream. 

I'm fortunate to have plenty of scrap copper available, so I prefer to use fresh copper in my first bucket rather than take the chance of adding any contaminants back into the first bucket. This keeps the cement in the first bucket pretty clean, since this is where I expect to find any precious metals.

Another thing to keep in mind is that Harold only used a single bucket with iron. Since he processed mass quantities of jewelers' waste, this made a lot of sense. He would use a magnet to remove all the iron from the waste he received and he added that to his stock pot. In this way, any precious metals that may have been mixed with the iron, e.g., bits of gold or platinum stuck to broken jewelers' saw blades, were not lost. As the iron blades were consumed in the stock pot, the values remained in the sludge.

I guess it depends on what type of scrap you process, and what processes you are able to use to treat the contents of your stock pot. Just keep in mind that it's not a clean, simple matter of PMs cementing on copper and copper cementing on iron.

Dave


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## kadriver (Mar 3, 2015)

Great info here, thanks to all who responded.

About 10 days ago I had 5 rings, I concluded that all were 14k but one was platinum And unmarked.

I did a gold test with 14k acid and it LOOKED like 14k gold.

As I inquarted I began to stir and the one ring was not melting very well.

I pulled it up on the side of the melt dish and added heat and part of it went into solution/alloyed with the molten gold and silver.

I pulled the remaining part of the intact ring out of the melt and put it in with other scraps of Pt that I am saving for later on after I have gained some more experience with PGMs.

After making flakes from the melt, I treated with dilute nitric acid and then tested the silver nitrate with stannous.

Sure enough it was loaded with platinum. I added this to my silver jar for cementing later on.

I processed the gold in the normal manner with AR and the waste (I call the left over SMB liquid after the gold has been precipitated, waste) was tested and showed high level of Pt also.

I added this waste to my stock pot that is charged with at least 20 pieces of fresh copper metal from cut-open copper tubing.

Last Friday I added about 5ml nitric acid to see if that would help get the platinum to cement out - stirring manually several times a day.

I was going to siphon my stock pot liquid (settled overnight) to my iron bucket today but first did a stannous test and bang, still platinum clearly visible (see picture).

I am going to get several aquarium bubblers and use these to start agitating the buckets. This Pt has been in the stock pot for about 10 days and it refuses to cement out completely.

This stock pot info has all been very helpful. Thanks again to all who gave input.

kadriver


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## kurtak (Mar 4, 2015)

FrugalRefiner said:


> I think it is important to remember that everything below iron will also cement out in this bucket, not just copper. This means you _could_ have a mix of copper, antimony, arsenic, bismuth, lead, tin, nickel, cobalt, cadmium, etc. if any of those metals are in your waste stream.
> 
> Dave



Very good point Dave.



> I'm fortunate to have plenty of scrap copper available, so I prefer to use fresh copper in my first bucket rather than take the chance of adding any contaminants back into the first bucket. This keeps the cement in the first bucket pretty clean, since this is where I expect to find any precious metals.



Due to the fact that most of my PMs come from dirty sources (electronics, contactor points etc.) I also use nothing but clean copper for cementing stock pot values & because I scrap metals in general I never have a shortage of clean copper on hand --- the copper I recover from cementing with iron gets melted & poured into 2 pound bars & sold as red brass to the scrap yard.



> I guess it depends on what type of scrap you process, and what processes you are able to use to treat the contents of your stock pot. Just keep in mind that it's not a clean, simple matter of PMs cementing on copper and copper cementing on iron.



Correct - if I was processing more - or nothing but sterling &/or coin silver & karat/dental scrap & didn't scrap other metals (which provides a cheap source of copper) I would then likely use my copper recovered from the iron cementing process --- but only then.

kadriver,

If there was a relatively high concentration of PGMs in your AR stock pot it may have already formed the passivation layer of PGMs on your copper that was giving me troubles which 4metals helped with (agitation) in the thread I provided a link to in my other post --- this passivation layer maybe somewhat of a problem if you try to re-use it in your AR stock pot - even with agitation now added.

At least it was for me when I tried re-using it in my AR stock pot after I got my bubbler --- so what I have been doing is adding my copper with the passivation layer to my silver nitrate solutions when cementing my silver - the silver nitrate seems to get under the passivation layer better then in an AR solution & the PGMs are then being recovered in the anode slime from the silver cell.

In fact if the AR stock pot has a "high" concentration of PGMs the passivation problem can still be "somewhat" of a problem - even with the bubbler - though certainly not as bad as without the bubbler.

I have found (since the discussion with 4metals) that when higher levels of PGMs are involved "fine" copper powder on the magnetic stirrer works better - you want to do it with small additions of copper powder - with time given to each addition to insure that all the copper has had time to dissolve & go into solution - more time needs to be given between additions as it nears the end - so there is a bit of a learning as you go curve - & of course stannous testing as you go near the end.

Here is a pic of a bus bar (right) used with a bubbler in AR high in PGMs - compared to one used to cement silver (left) first day in the bubbler most of the PGMs came down but still had a PGM positive stannous test --- 3 days later it was still testing PGM positive so stopped it & went to copper powder on the magnetic stirrer - a few hours later I had the rest of my PGMs with a negative stannous test.

Kurt


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## kadriver (Mar 4, 2015)

Excellent Kurt, I got two aquarium bubblers today at WalMart, about $7 each.

I have 5/16 clear tubing with a 12 inch length of rigid tubing at the end to keep it directed at the bottom of the buckets.

Copper powder, magnetic stirrer treatment for stubborn PGMs - that is very good to know.

Also withdrawing copper with passive layer from the stock pot and using it to cement silver, I never would have done that. Thanks for that tip.

I concluded that after the PGMs are cemented with the stir and copper powder that the solids are returned to the stock pot.

Great info - thank you!

kadriver


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## nickvc (Mar 5, 2015)

As has been said it really does depend on the quantities and sort of materials you refine and recover as to what the best route is with stockpots. I always had a settlement tank to allow any fines to settle to the bottom with added precipitant then two stockpots the first loaded with copper the second with a little steel added fresh every time it was full. The last stockpot contents were added back into the first every now and then depending on how much material I had in my system, the last stockpot I worked on the theory if I could cement copper out all the values especially any PGMs should have also been cemented out and could be recovered later from the first stockpot.


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## jason_recliner (Mar 10, 2015)

kurtak said:


> MarcoP said:
> 
> 
> > As a side note, why aren't you using calcium hydroxide for waste treatments? It's easy cheaper then sodium hydroxide and little easy to filter off. I can buy 25Kg locally at €3-€3.50.
> ...


I've just exhausted my NaOH on my waste so I'm going to buy some calcium hydroxide as per your excellent suggestion. Here's a follow up for anyone else playing at home.
It's a bit hard to buy "calcium hydroxide". As I researched bulk limes, you might find the right one in your local Bunnings / Mitre 10 / Lowes as "builder's lime" or "hydrated lime". On the other hand, "lime" from the garden centre may well be calcium magnesium carbonate. Just keep an eye on the fine print or MSDS.


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## MarcoP (Mar 10, 2015)

I was finally able to find the english product's name of what I'm using: lime wash paint, basically slaked like (calcium hydroxide) in water.


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## kurtak (Mar 11, 2015)

Calcium carbonate works just fine - it's what I use - I buy what is called "barn lime" (used by dairy farmers to spread on their barn floors) any feed/farm supply store should have it & it is dirt cheap - it takes 2 - 3 days with stirring it a few times a day to complete the reaction.

Kurt


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## 4metals (May 12, 2015)

The moderators would like to thank all of the members that contributed to the original thread upon which this thread was based, as well as those that asked questions showing what was missing. Because of the extra length and interest in this thread we have created the above consolidated version making for an easier read. We encourage all members to read, comment, and ask questions in the original thread, The Stock Pot

The Library threads should not be considered to constitute a complete education. Instead, they're more like reading a single book on the subject of recovery and refining. There is so much more information on the forum, and it is impossible to include it all in these condensed threads. Members are strongly encouraged to read the rest of the forum to round out their education.

For those who prefer a printed copy, a pdf file of this thread is provided below.


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