The Stock Pot

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, it's function was not all that clear. I have been doing small-tine 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

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.

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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.

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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).

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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)?

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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

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

g_axelsson said:

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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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

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.

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

kadriver said:

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.

Click to expand...

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

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

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The typical ice cream bucket. Don't happen to have on 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

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.

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.

Just be carefull 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.

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 profected. 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 their is always copper still in the bottom of the bucket which lets me know i'm good to go. To 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.

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 very because of the plastic revolution if you will.

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 grip 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 their 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.

kadriver
Excellent idea with stock pot systems in 1 place.

That crock you have pictured is worth allot 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 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

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. Them 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.

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 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 eat up.

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

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

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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

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?

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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.

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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