# Can I use large chemical drums for dissolving?



## ssharktu17 (Jan 20, 2022)

I have access to 55g chemical drums they are food grade used to hold acids for cleaning. 

Also, as far as nitric acid everyone says 67-70% but what if I have access to 25% or 30% at a much lower cost? Are there impurities or is it just more dilute. Considering the first step in dissolving silver is diluting the acid 50% why not just start with 35%?


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## FrugalRefiner (Jan 20, 2022)

It's hard to answer your first question without knowing what the chemical drums are made from and what you intend to dissolve.

Not knowing anything about the acid you can buy, we can't know if there are any impurities. There should be an analysis available that would tell you what impurities might be included.

If there are no significant impurities, you can certainly use the lower concentration to dissolve silver.

Dave


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## Quiklearner (Jan 20, 2022)

Far from an expert here, but storing chemilcals at ambient temperatures is a lot different than containing acids during a chemical reaction. Heat is generated (or often added as a requirement) and hot acids behave differently than they do when cold. Like Dave said above, more info is needed. I'd go out on a limb though and say that it isn't advisable...


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## ssharktu17 (Jan 20, 2022)

Quiklearner said:


> Far from an expert here, but storing chemilcals at ambient temperatures is a lot different than containing acids during a chemical reaction. Heat is generated (or often added as a requirement) and hot acids behave differently than they do when cold. Like Dave said above, more info is needed. I'd go out on a limb though and say that it isn't advisable...


I have seen people running the reaction in 5g buckets so I thought it might be fine.


FrugalRefiner said:


> It's hard to answer your first question without knowing what the chemical drums are made from and what you intend to dissolve.
> 
> Not knowing anything about the acid you can buy, we can't know if there are any impurities. There should be an analysis available that would tell you what impurities might be included.
> 
> ...


Any specific contaminants to watch out for? The drums are HDPE resin.


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## Quiklearner (Jan 20, 2022)

I'm sorry, I have no recommendations in this area my friend... I'm just a small scale hobby operation using borosilicate glassware only.


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## Quiklearner (Jan 20, 2022)

I too have seen it done in plastic pails/buckets and such, but often those same videos show people wearing Crocs (a type of sandal for your feet) and I don't think that is advisable either


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## FrugalRefiner (Jan 20, 2022)

ssharktu17 said:


> I have seen people running the reaction in 5g buckets so I thought it might be fine.
> 
> Any specific contaminants to watch out for? The drums are HDPE resin.


I was hoping they might have been stainless steel drums. I wouldn't personally recommend them for dissolving silver with nitric. As Quicklearner mentioned, storing acid is different than running reactions. Nitric will slowly attack HDPE, making it brittle. Heat will speed that attack.

I don't have a list of contaminants to watch for. They should be in the very low fractions of a percentage.

Dave


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## ssharktu17 (Jan 20, 2022)

FrugalRefiner said:


> I was hoping they might have been stainless steel drums. I wouldn't personally recommend them for dissolving silver with nitric. As Quicklearner mentioned, storing acid is different than running reactions. Nitric will slowly attack HDPE, making it brittle. Heat will speed that attack.
> 
> I don't have a list of contaminants to watch for. They should be in the very low fractions of a percentage.
> 
> Dave


Hmm well I am hoping to do some larger batches and glass/stainless would certainly be prohibitively expensive. I have lots of 55g HDPE drums so I could use a new one for each dissolve. But I definitely wouldnt want it to dissolve onto the ground lol. Maybe I will do a 35 gallon drum within a 55g.


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## kurtak (Jan 21, 2022)

ssharktu17 said:


> Hmm well I am hoping to do some larger batches



Large batches of what & what do you consider "large"

Kurt


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## ssharktu17 (Jan 21, 2022)

kurtak said:


> Large batches of what & what do you consider "large"
> 
> KurtN



Nitric plus sterling. Maybe doing 1000ozt at a time of sterling.


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## kurtak (Jan 21, 2022)

If you are doing silver here is a 90 liter stainless steel pot (so a bit over 20 gallons) for $138

Not a bad price for a 20 gallon reaction vessel - if silver is what you are doing (or any other "nitric only" process like dissolving copper for gold recovery from pins &/or fingers)

Kurt









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## ssharktu17 (Jan 21, 2022)

kurtak said:


> If you are doing silver here is a 90 liter stainless steel pot (so a bit over 20 gallons) for $138
> 
> Not a bad price for a 20 gallon reaction vessel - if silver is what you are doing (or any other "nitric only" process like dissolving copper for gold recovery from pins &/or fingers)
> 
> ...


Hey that’s not too bad! And stainless is fine it won’t contaminate at all?


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## kurtak (Jan 22, 2022)

ssharktu17 said:


> Hey that’s not too bad! *And stainless is fine it won’t contaminate at all*?



Per the bold print - nitric acid does not react with stainless steel - that is why on a commercial/industrial scale nitric is shipped & stored in stainless steel drums - when I was refining on a large scale I got my 67% nitric which came in 15 gallon SS kegs (drums) or 52% nitric which came in 55 gallon drums

Keep in mind that you will be charged a HIGH deposit on the drums - but you get that deposit back when you return the drum (or goes to the next drum of acid if you exchange the empty drum for another new drum of acid)

Also - you need to check with the company you get your acid from as they may have a time limit on how long the deposit is good for - if you go beyond that time limit (for retuning the drum) the deposit become a purchase & the drum becomes yours 

The bottom line being - yes a large SS pot will work just fine for dissolving your sterling - large SS pots are what I used for processing my silver as well as processing large batches of fingers, pins &/or gold filled to dissolve the copper/brass to recover the gold foils

Again - SS works just fine as long as you are using nitric *ONLY* - it will not work with AR or HCl reactions as AR & HCl both react with SS 



ssharktu17 said:


> Nitric plus sterling. Maybe doing 1000ozt at a time of sterling.



Keep in mind that it takes "*about*" 1 gallon of 67 - 70% nitric (plus 1 gallon distilled water) to dissolve "*about*" 8 pounds of silver but it will only dissolve "*about*" 2 pounds of copper/brass

Due to "heavy" foaming at the peak of your reaction you only want to fill your reaction vessel "*about*" 1/3 full with the acid/water (to be safe from having a foam over)

I keep saying "*about*" because how much foaming you have & how much acid it will take to dissolve a given amount of metal will depend "*a lot*" on the conditions when dissolving that metal

So using rough figures (& using 67 - 70% nitic) ---------

A 90 liter pot = about 23 gallons - divided by 3 (you only want to fill 1/3 full - to start with) = about 7.8 gallons (call it 8 gallons) --- so 50/50 acid/water = 4 gallons acid --- which will dissolve "*about*" 32 pounds of silver

A pound of silver is "about" 14.5 ozt - so - 32 X 14.5 = 464 ozt

In reality - IF (the BIG IF) you control the conditions you use to dissolve your sterling - you should be able to dissolve (plus/minus) about 500 ozt sterling --- so about 1/2 the size batches you are wanting to do

So here is another large pot you may want to consider if you are wanting to do 1000 ozt batches as it is double the size I posted yesterday (180 liters or 45 gallons) for $230









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You can use a propane turkey fryer burner for you heat source - you will want to put a 5/16 inch thick steel plate on top the turkey fryer burner & then put the pot on that 

This set up is going to be very top heavy so you need to weld up a frame/base to the turkey fryer burner to stabilize it & keep it from tipping over

Kurt


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## kurtak (Jan 22, 2022)

Here are a couple of links to information I have post concerning *the conditions* you need to consider when dissolving metal with acid

The *conditions* can/will make a *BIG* difference in the amount of acid you will end up using to dissolve a given amount of metal

Once you understand these conditions you can use them to your advantage to dissolve *more* metal with *less* acid

Read *everything* I posted in these threads &/or follow any links in those postings









Dissolving the Copper in Sterling (nitric Qty?)


I'm trying to determine how much nitric I need. I've read that about 2ml will dissolve 1gr of silver. But how much more to account for the copper? For example, if I had enough sterling to yield 10ozt silver, I'd also have about 1ozt copper. According to my calculations I'd need about 660ml to...




goldrefiningforum.com













Anywhere to buy nitric reasonably cheap?


Sounds like a silver Cell would be far more economical considering the price of nitric.




goldrefiningforum.com





Kurt


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## ssharktu17 (Jan 22, 2022)

kurtak said:


> Per the bold print - nitric acid does not react with stainless steel - that is why on a commercial/industrial scale nitric is shipped & stored in stainless steel drums - when I was refining on a large scale I got my 67% nitric which came in 15 gallon SS kegs (drums) or 52% nitric which came in 55 gallon drums
> 
> Keep in mind that you will be charged a HIGH deposit on the drums - but you get that deposit back when you return the drum (or goes to the next drum of acid if you exchange the empty drum for another new drum of acid)
> 
> ...


Thank you! What is the purpose of the steel plate on top of the turkey fryer?


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## silver1 (Jan 22, 2022)

Those are thin guage stainless. Where the material lays in the bottom and is heated you will have a corrosion effect. Pin holes and leaks will develop within a few cycles.


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## orvi (Jan 23, 2022)

ssharktu17 said:


> Hey that’s not too bad! And stainless is fine it won’t contaminate at all?


Also note that covered by meaning "stainless steel", there is immense number of different alloys of SS. Without knowing the material of the pot EXACTLY, do not buy it. There are some cheap low-end soft manganese/low Cr-Ni stainless steel alloys, mainly used in budget gastro devices.* These are complete crap and will be slowly attacked by nitric - personal experience*.

_Very very unpleasant to witness electric hotplate half-dissolved in puddle of nitric inside of catching crate, overgrown with cement silver from every side. Not a good start for a new week in work  This incident was just 10 L vessel. I warned about this, warning was ignored, accident happened. 
_
Check the compatibility charts of the certain alloy with nitric acid at VARIOUS CONCENTRATIONS and TEMPERATURES as you opt for buying the big expensive pot - not to make big expensive drainage of 100 L silver-nitric  

Even heating of the vessel is also very important, as overheating certain areas could cause "bumping" on the bottom - cavitation will rip off the pieces of protective oxide layer slowly. What ultimately leads to developing holes and cavities, where most intense heat is applied. I also recommend not to boil the solution inside - less cavitation possible = less damage = longer service.


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## kurtak (Jan 23, 2022)

silver1 said:


> Those are thin guage stainless. Where the material lays in the bottom and is heated you will have a corrosion effect. Pin holes and leaks will develop within a few cycles.


If you are talking about cheap SS pots like these from harbor freight then yes they can/will develop pin holes as you say

They are made of something like 21 gauge SS (so VERY thin) 






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the pin holes develop where the heat from your heat source is concentrated on the bottom of your pot - such as where the flame from a propane burner - or the coils of an electric hot plate are in direct contact with the bottom of the pot

That is why I suggested putting a 3/8 - 5/16 steel plate on the turkey fryer burner then setting the pot on the plate

the plate acts as a heat spreader giving an even heat across the bottom of the pot - so no "hot spots" where the flame or coils are in direct contact with the bottom of the pot 

A 3/8 - 5/16 steel plate wont warp from the heat - a thinner plate (like 1/4 inch will likely warp (my plate is 5/16 & cut round) & yes you want it cut round as again that helps with even heat distribution (otherwise heat tries to sink out to square corners)

Normally speaking (but not always true) those LARGE stock pots are made of heavier gauge SS like 18 - 16 gauge --- there is a BIG difference between 22 - 20 gauge & 18 - 16 gauge

The links I provided did not give specs (like thickness/gauge of the pots) I was simply pointing out that LARGE SS pots are out there - also - those particular pots *may* (or not) have a welded seam (were the black strip is) I would not use a pot with a welded seam

ssharkto17 needs to do some shopping & contact the company & ask about the gauge/thickness of the pots as well as if it has a welded seam or not (if buying on line)

18 gauge &/or even better 16 gauge will hold up just fine

The best is to go to a local home brew supply store & see what they have as you actually get to look at the pots & ask questions

A home brew store is were I got my large pot (20 gallon) which was heavier gauge (then the cheap harbor freight pots) & if memory serves me right I believe a paid something like $369 - $379 for it & it served me well for years & more then paid for itself --- that was like 15 years ago so price has likely gone up (or not) but as the saying goes (though not always true) you get what you pay for

Also - palladium at one time posted a pic of his set up using a LARGE SS pot (which I can't find again) I am not sure he logs in on the forum anymore - but if he does & sees this thread maybe he will chime in with info &/or repost that pic of his set up

Kurt


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## kurtak (Jan 23, 2022)

orvi said:


> Also note that covered by meaning "stainless steel", there is immense number of different alloys of SS. Without knowing the material of the pot EXACTLY, do not buy it. There are some cheap low-end soft manganese/low Cr-Ni stainless steel alloys, mainly used in budget gastro devices.* These are complete crap and will be slowly attacked by nitric - personal experience*.
> 
> _Very very unpleasant to witness electric hotplate half-dissolved in puddle of nitric inside of catching crate, overgrown with cement silver from every side. Not a good start for a new week in work  This incident was just 10 L vessel. I warned about this, warning was ignored, accident happened. _
> 
> ...



Per the bold print (I high lighted) --- correct & well said which is why I posted about needing the steel plate between the burner & pot

Concerning heat --- you do not need to provide *constant* heat (from first starting to dissolve your silver or copper until you are done dissolving the metal)

You only need to apply heat to get the reaction going - once the reaction gets going you can turn the heat off as the heat from the reaction will drive the reaction on it's own - then once the (self driving) reaction (near the end) dies down you can turn the heat back on were/when heat is once again needed to "finish" driving the reaction

You don't need a lot of heat - just enough to drive the reaction (all part of the learning curve) 

Also concerning the SS alloy - you want 304 or 316 SS

Also - beware that Made In China puts out some cheap stuff that is not true to their claim (as to claimed alloy) so look for Made In U.S.A as U.S made normally has tighter controls on their alloys

Again - as I said in my last post - the links for the large pots I provided are only examples that large pots are out there - you need to do some shopping & ask questions

Kurt


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## orvi (Jan 23, 2022)

kurtak said:


> Per the bold print (I high lighted) --- correct & well said which is why I posted about needing the steel plate between the burner & pot
> 
> Concerning heat --- you do not need to provide *constant* heat (from first starting to dissolve your silver or copper until you are done dissolving the metal)
> 
> ...


Well said.

If one have a vessel on hand, and is going to process thousands of oz as proposed, I think it will be possible to XRF the concerned vessels to know what material (which type of stainless) it is. 

Yes, heat is needed just from the start. If good insulation of the pot is assured, it will be self-sustaining heat for very very long time. But caution is needed, as over-insulating could result in vigorous reactions and boil-overs. However, silver is more "tame" when comes to comparison of reaction rate with copper.

_Issued low-quality manganese/low Cr-Ni stainless - we purchased good ammount of thin-wall modular stainless steel "bowls" used in gastro - for chilling/heating meals, used for ice cream etc... (reactangular shape). Primarily, we wanted to use them as burning trays for incineration assays for various materials - perforate them from the bottom. Then, very elegant idea arised - nitric do not attack stainless - let´s cook dore in it, directly on the electric heater - very convinient, no duplicator necessary._ _Well, first one or two days, the smaller experiment looked OK, vessel just turned dark on the inside, but nothing major. So big one was used... Heating for like 3 days on low heat and boom - contents found their way out from the bowl 
We XRF-ed the material before to know what kind of metal it is, issuing the very low price (like 5-6 euros for 1,5-2 L vessel). I did not like the overall idea, but I was not in the charge of this operation _


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## kurtak (Jan 23, 2022)

One more thing I would like to ask --- why are you wanting to refine your sterling ?

I ask because unless you have a market already established wherein you can sell your refined silver for a premium *above* spot you are likely not going to make any more money by refining it as opposed to selling the sterling directly to a refinery

In other words - most refineries are going to pay you the same price (for the silver in your sterling) as they will pay you for your refined silver 

Example; - the refinery I send my silver to - they pay me 93% of spot as long as I send them a minimum of 500 ozt silver whether it is 999 (plus) or sterling

to clarify - with the sterling - to get the 93% spot price - the sterling has to have (minimum) 500 ozt silver *in it* - so I have to send them (about) 550 ozt of sterling in order to have 500 ozt actual silver

On the other hand - if I refine it to 999 (plus) I still only get 93% spot as long as it's the (minimum) 500 ozt of silver

So - for the most part I simply send my sterling directly to the refinery

Most of the silver I actually refined was lower grade silver such as contact points (due to cadmium which some refineries deduct for) silver solder/braze, low grade foreign coins, silver sulfide recovered from picture fixer solutions, or silver recovered from doing gold filled, etc.

Also - I did have a few buyers that would buy my refined silver for a premium above spot but those markets (buyers) were limited in buying (a few kilos) at a time so it was worth having some refined silver on hand for when they wanted to buy

other then that most of my sterling I sold directly to the refinery as I got paid the same (on the silver) whether it was sterling or 999 plus refined

Kurt


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## silver1 (Jan 23, 2022)

304 stainless drum wielded to a 3/8 304 stainless plate sitting on a all stainless cooker.
Total cost... Just North of $1,000.


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## Quiklearner (Jan 23, 2022)

Talk about reaction vessel envy!!!


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## silver1 (Jan 23, 2022)

Quiklearner said:


> Talk about reaction vessel envy!!!


You can see the set up here.


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## Quiklearner (Jan 23, 2022)

@silver1: I've seen some of your previous videos. Glad to see you back and thanks for sharing your knowledge!


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## ssharktu17 (Jan 24, 2022)

kurtak said:


> One more thing I would like to ask --- why are you wanting to refine your sterling ?
> 
> I ask because unless you have a market already established wherein you can sell your refined silver for a premium *above* spot you are likely not going to make any more money by refining it as opposed to selling the sterling directly to a refinery
> 
> ...


I buy as an investment mostly so for me I am the end buyer. I would rather have bars than piles of scrap. But if I can get scrap far cheaper it makes sense. I might pour some 1 oz rounds and try to sell them just for some cash flow but mostly I just want to have bars instead of scrap and I would save a lot of money doing it myself vs selling to a refiner and then buying bars at a premium.


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## kurtak (Jan 24, 2022)

ssharktu17 said:


> I buy as an investment mostly so for me I am the end buyer. I would rather have bars than piles of scrap. But if I can get scrap far cheaper it makes sense. I might pour some 1 oz rounds and try to sell them just for some cash flow but mostly I just want to have bars instead of scrap and I would save a lot of money doing it myself vs selling to a refiner and then buying bars at a premium.



I don't want to tell you what to do - but - if all you are doing is "stacking" your silver there is a better route to go (IMO)

Instead of buying LOTS of nitric - setting up to dissolve "large" batches of sterling - then cementing the silver back out of the silver nitrate - then pouring shot or bars to run in a silver cell - then having to deal with all the chemical waste you will have to deal with in that process --- & other things you will need to invest in to set up for this kind of full on refining (like a real lab with fume hood, chem storage, fume scrubber, furnace for melting your end product, etc. etc. etc.)

Keep it simple - get a propane furnace that will hold a number 4 crucible (not one of those "cheap" electric furnaces) along with a 1 kilo cast iron mold - melt your sterling & pour kilo bars - get some number stamps & stamp them with 925

Kilo bars "stack" very nice & take up MUCH less room then a bunch of sterling scrap (like flatware, trays, bowls, trophies, etc.)

Then - if - you want to refine "some" of that sterling to make "some" 999 plus silver for making 1 ozt rounds/bars you can run those kilo bars in a silver cell to get your 999 plus silver --- if all you are really wanting to do is "some" small batch 999 (plus) for "some" rounds/bars

This set up - on a small(er) scale will take MUCH less investment MUCH less chems & create MUCH less chem waste (the chem waste being the elephant in the room) 

Your kilo bars of sterling aren't going to go anywhere - until you want them to - whether that be send them into a refiner - or refine them your self

At least that is how I do it - all my sterling is poured to kilo bars - IF (the BIG IF) I decide to ship to the refinery the kilo bars are already poured & take up much less room (box) for shipping - or - if one of my clients that pays a bit more then spot for 999 (plus) calls for some 999 (plus) I fire up my cell & run the sterling kilo bars as anodes in the cell

You can turn out 9999 silver in the cell as long as you understand when/how to control the copper corruption of the electrolyte when running the cell --- part of the learning curve

For what it is worth

Kurt


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## ssharktu17 (Jan 24, 2022)

kurtak said:


> I don't want to tell you what to do - but - if all you are doing is "stacking" your silver there is a better route to go (IMO)
> 
> Instead of buying LOTS of nitric - setting up to dissolve "large" batches of sterling - then cementing the silver back out of the silver nitrate - then pouring shot or bars to run in a silver cell - then having to deal with all the chemical waste you will have to deal with in that process --- & other things you will need to invest in to set up for this kind of full on refining (like a real lab with fume hood, chem storage, fume scrubber, furnace for melting your end product, etc. etc. etc.)
> 
> ...


Thanks Kurt definitely great advice! I have heard mixed opinions on using silver cell for 925 but it does seem practical and probably a lot cheaper. Ill have to research it more. I do like the idea of melting 925 into shot or bars and just storing that for now.


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## orvi (Jan 24, 2022)

ssharktu17 said:


> Thanks Kurt definitely great advice! I have heard mixed opinions on using silver cell for 925 but it does seem practical and probably a lot cheaper. Ill have to research it more. I do like the idea of melting 925 into shot or bars and just storing that for now.


Some people refine with two silver cells in series. They pour the shot/anode bars from sterling, run them first time through the "dirty" cell to obtain crude "99+" silver, leaving all base metal junk in the first pot. You must deal with the accumulating copper anyway, but to obtain 99% silver from sterling, you can go quite high with copper content in the cell  Then this refined silver undergo second "pure" cell rafination to 999+ purity, not compromising the "pure" electrolyte with tons of copper 
It is good to make calculation about how expensive the nitric dissolution pathway is vs. how effectively you can do scheme mentioned above - double silver cell. Labor vs. cost.
To me, double cell method is much cleaner, no clouds of NO2 are produced. Aside of making AgNO3 electrolyte for the first run.


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## kurtak (Jan 25, 2022)

orvi said:


> Some people refine with two silver cells in series. They pour the shot/anode bars from sterling, run them first time through the "dirty" cell to obtain crude "99+" silver, leaving all base metal junk in the first pot. You must deal with the accumulating copper anyway, but to obtain 99% silver from sterling, you can go quite high with copper content in the cell  Then this refined silver undergo second "pure" cell rafination to 999+ purity, not compromising the "pure" electrolyte with tons of copper
> It is good to make calculation about how expensive the nitric dissolution pathway is vs. how effectively you can do scheme mentioned above - double silver cell. Labor vs. cost.
> To me, double cell method is much cleaner, no clouds of NO2 are produced. Aside of making AgNO3 electrolyte for the first run.



You can also "extend" you run time before copper starts co-depositing by increasing the silver concentration of the electrolyte you start with as the copper does not start co-depositing until silver ions are reduced & replaced by copper ions --- so if you start with a higher silver concentration you can run the cell longer before you upset the balance between silver ions & copper ions in the electrolyte causing the copper to co-deposit

OR - when you figure the copper ions are close to corrupting the electrolyte to the point of co-depositing you can siphon off half your corrupted electrolyte & replace it with fresh electrolyte

Ether &/or both of those things will extend you run time before concern for copper co-depositing --- again - there is a learning curve

As the saying goes - there is more then one way to skin a cat --- running a "break down" cell & then running a second purification cell is one of those ways 

Kurt


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## snoman701 (Jan 25, 2022)

The only way to beat a silver cell for doing sterling is to do formate reduction. In a large scale, I think you underestimate the difficulty of filtration of your silver cement. 

Cheapest entry into a good barrel to dissolve silver is a keg. Cut the top off it. You can get them on facebook marketplace as they are directed at the home brew crowd. 

I've used quite a few different stainless pots for silver. I am running 100% for destroying them...but alas, that is life. I had a really nice pasta cooker that I loved. It held up great til the handle broke off, then it went downhill fast. 

The fumes will be a lot easier to handle on a silver cell than they will straight dissolution as well.


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## ssharktu17 (Jan 25, 2022)

snoman701 said:


> The only way to beat a silver cell for doing sterling is to do formate reduction. In a large scale, I think you underestimate the difficulty of filtration of your silver cement.
> 
> Cheapest entry into a good barrel to dissolve silver is a keg. Cut the top off it. You can get them on facebook marketplace as they are directed at the home brew crowd.
> 
> ...


What do you mean the difficulty of filtration of the cement?


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## ssharktu17 (Jan 25, 2022)

snoman701 said:


> The only way to beat a silver cell for doing sterling is to do formate reduction. In a large scale, I think you underestimate the difficulty of filtration of your silver cement.
> 
> Cheapest entry into a good barrel to dissolve silver is a keg. Cut the top off it. You can get them on facebook marketplace as they are directed at the home brew crowd.
> 
> ...


Formate reduction sounds interesting more research to do lol


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## snoman701 (Jan 25, 2022)

ssharktu17 said:


> What do you mean the difficulty of filtration of the cement?


Have you ever seen 1,000 oz of silver cement? Dissolving the silver is the easy part, and frankly, in terms of infrastructure, the cheap part. 

Go price a 24" buchner funnel.

I've got 4 different 25 cm funnels and and assortment of receiving flasks and pumps....

1,000 oz silver you should eb able to get 95% accountability easily, and pay $1 an oz to get a minted product back to you. At current silver prices, that's $2400. I have four 25 cm buchners, the vacuum flasks, dissolution containers, etc etc. Well over $2400 and I am not able to do 1,000 oz lots nearly competitevly. Sometimes it's best to just pay up.


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## silver1 (Jan 25, 2022)

ssharktu17 said:


> Formate reduction sounds interesting more research to do lol


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## silver1 (Jan 25, 2022)

snoman701 said:


> Have you ever seen 1,000 oz of silver cement? Dissolving the silver is the easy part, and frankly, in terms of infrastructure, the cheap part.


AMEN! The dissolving is the easy part. Filtering and drying is a pain in the ....
I have a stainless restaurant griddle like the waffle house uses. About 3 ft X 6 ft. I can throw 100 lbs of powder on it and stir it around like hash browns with a large stainless sheet rock knife. I can dry about 100 lbs in 30 minutes.


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## ssharktu17 (Jan 25, 2022)

silver1 said:


> AMEN! The dissolving is the easy part. Filtering and drying is a pain in the ....
> I have a stainless restaurant griddle like the waffle house uses. About 3 ft X 6 ft. I can throw 100 lbs of powder on it and stir it around like hash browns with a large stainless sheet rock knife. I can dry about 100 lbs in 30 minutes.


Does it really even have to be dry wouldn’t the 2000F dry it up pretty quick?


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## silver1 (Jan 25, 2022)

Any water left in the powder will need to evaporate before it can start melting. As water evaporates it robs the furnace of heat to convert that water to vapor. You will either expend energy in the drying phase or in the furnace phase. Either which way there is no free lunch. It's more about time and efficency. On a small scale that might not matter, but as you scale up it comes into play. A lot of my clients like it returned in powder form. In order to do proper weighing and fee calculations i have to have it dry.


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## ssharktu17 (Jan 25, 2022)

silver1 said:


> Any water left in the powder will need to evaporate before it can start melting. As water evaporates it robs the furnace of heat to convert that water to vapor. You will either expend energy in the drying phase or in the furnace phase. Either which way there is no free lunch. It's more about time and efficency. On a small scale that might not matter, but as you scale up it comes into play. A lot of my clients like it returned in powder form. In order to do proper weighing and fee calculations i have to have it dry.


Ah I hear ya. That definitely makes sense for sending back powder. I guess I probably wouldn’t care much planning to use free waste oil so burning off the water probably won’t matter much. Maybe let the powder bake in the 100 degree sun for a few days before.


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## kurtak (Jan 26, 2022)

snowman & silver 1 - you guys are *awesome* - thanks for contributing to this thread

As the saying goes - there is more then one way to skin a cat --- skinning cats different ways is part of the love of refining (IMO)

For what it's worth --- I would say about half the silver I processed I got from magnetic disconnects

I got the disconnects by the pickup truck load from a couple scrap yards I delt with 

Some of those disconnects had points in them that had 1 ozt silver per contact point/pad - so 12 ozt silver per disconnect - & when you have a pickup load of them it's a *PAY DAY*

Anyway - just wanted to say you guys are *awesome* & are part of what makes this forum worth being a member of

Kurt


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## orvi (Jan 26, 2022)

ssharktu17 said:


> Does it really even have to be dry wouldn’t the 2000F dry it up pretty quick?


Depends.

You must consider everything. Drying few kg of silver powder in a crucible is not the most effective way to do it. Slow heat transfer, very high evaporation enthalpy... With few kg risk of steam explosion is a real concern - not very probable, but certainly nothing very pleasant to experience.
Everybody who I know melt the cement dry. Only for batches less than half kilo, some do not dry it to the powder and melt directly (whole cake with filter paper) - saving time as this is mostly "assaying" practice, just to assume how the bigger lot will go.



ssharktu17 said:


> What do you mean the difficulty of filtration of the cement?



Filtering is easy to the point when the equipment is easily manageable with bare hands. Biggest Buchner funel what I ever seen was 40 cm in diameter and weighed few kilograms  

Depending on how you prepare the cement, it will be ranging from fluffy powder to dense powder. Filtering the solution before cementation is very advised, because presence of opalescence or insoluble metastannic from some soldering could cause formation of non-settling very fine particles. 
You can easily end up with 100g of dry powder occupying volume of 50 ml or more. If this happen, for 30 kg of silver, you will need something capable of holding 15 L when filtering. Or two set-ups for say 8 L each. 
Nice hack with two buckets filtering was presented above could resolve this.

If you have time, decanting is also option, but it is very slow and volume of waste to treat is immense. Not saying how you will dry the sludge at the bottom of the drum efficiently.

With 1000ozt of silver cement, you are way above the sane capacity of the regular laboratory glassware/dishes. 
Slowly stepping to the field, where in commercial facility, everything is elegantly pumped via expensive resistant pumps, dryied in rotary vacuum ovens or filtered on rotating continous vacuum filtering drum with scraper blades 

You must be very creative in the way how to deal with medium size production line in your garage, limited budget and tight margins. Simple operation like pouring the cement from the cementation drum to the filter is quite tricky operation, when there is hundred liters of the juice and say 30kg of silver powder. How you get the solid safely to the filter without splashing ? How you wash the solids throughly when the cake is 80 cm high ? How would you protect yourself comfortably - working with liters of AgNO3 solution, there is no way how you can protect yourself from minor splashing etc. with simple PPE - it become just matter of time. You need to resolve this, otherwise you will soon be covered with brown patches all over your body  not joking. This is quite serious thing, silver nitrate stain the skin in so minor concentrations... etc

This is not meant to discourage you, but to give you the other perspective of mid-size refining 
Stay safe.


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## ssharktu17 (Jan 26, 2022)

orvi said:


> Depends.
> 
> You must consider everything. Drying few kg of silver powder in a crucible is not the most effective way to do it. Slow heat transfer, very high evaporation enthalpy... With few kg risk of steam explosion is a real concern - not very probable, but certainly nothing very pleasant to experience.
> Everybody who I know melt the cement dry. Only for batches less than half kilo, some do not dry it to the powder and melt directly (whole cake with filter paper) - saving time as this is mostly "assaying" practice, just to assume how the bigger lot will go.
> ...


Many things to consider. I will certainly have to start with small batches and then scale up appropriately. I dindt even know about the AgNO3 staining thats definitely something to consider. Thanks again for the input!


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## FrugalRefiner (Jan 26, 2022)

orvi said:


> How would you protect yourself comfortably - working with liters of AgNO3 solution, there is no way how you can protect yourself from minor splashing etc. with simple PPE - it become just matter of time. You need to resolve this, otherwise you will soon be covered with brown patches all over your body  not joking. This is quite serious thing, silver nitrate stain the skin in so minor concentrations... etc


I have to relate an experience I had. I was dissolving a small amount of silver. My back acted up on me, and I had to leave it for a bit. It got spilled and some of it ended up on a tarp. When I felt better, I cleaned up the mess. I didn't realize there was dried silver nitrate on the tarp when I handled it.

I went for a walk later in the day. It was a nice sunny day. As I got back to our house, I checked the mail box and was shocked at several large black stains on my hands. It was silver nitrate. Took days for it to disappear.

Dave


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## snoman701 (Jan 26, 2022)

HA

The stains are frustrating as heck. My right thumb, index and middle finger all have streaks. I wear gloves for 99% of my time in the lab. That remaining 1% got me. 

But frankly, I'm not concerned about the SILVER. It's the other metals that are also in solution that are more bothersome.

I think it's funny when people come in and want to work with this stuff. Mostly because all of us look back at our younger selves and go "noooo, don't do it....here are all the things you aren't considering"


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## silver1 (Jan 26, 2022)

I took the back side of my glove and wiped my eye one time thinking the back side was clean.
People ask me for a week who punched me in my eye!


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## silver1 (Jan 26, 2022)

snoman701 said:


> But frankly, I'm not concerned about the SILVER. It's the other metals that are also in solution that are more bothersome.


 Nope! Never worry about pure silver at all. Matter of fact i smoke a daily dose of it. Haven't been sick in years. Now the other stuff.....
I take NAC on a daily basis just to be healthy and safe. NAC will help pull that stuff out of you.


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## snoman701 (Jan 26, 2022)

silver1 said:


> Nope! Never worry about pure silver at all. Matter of fact i smoke a daily dose of it. Haven't been sick in years. Now the other stuff.....
> I take NAC on a daily basis just to be healthy and safe. NAC will help pull that stuff out of you.



I don't get the pleasure of pure silver very often. When I run a cell, that's the closest I get.


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## orvi (Jan 27, 2022)

snoman701 said:


> The stains are frustrating as heck. My right thumb, index and middle finger all have streaks. I wear gloves for 99% of my time in the lab. That remaining 1% got me.
> 
> But frankly, I'm not concerned about the SILVER. It's the other metals that are also in solution that are more bothersome.
> 
> I think it's funny when people come in and want to work with this stuff. Mostly because all of us look back at our younger selves and go "noooo, don't do it....here are all the things you aren't considering"


I found staining myself most probably like this: 
1. properly wearing gloves all day long, working with buckets, siphoning, mixing, decanting, filtering etc...
2. realizing i have dirty gloves on, touching every item and transfering the silver nitrate on everything in minute ammounts.
3. when drying the powder, i start the cleanup - also with gloves, knowing about this phenomena
4. forgetting about some ONE thing that I touched - and putting my bare hand on it
5. thinking how this could happen to me everytime i do silver 

_I was exactly like this. Head first to my first batch of contact points. Going with few hundred grams to see how things go ? Noooooo. Straight 3 kg  and as I commited this decision, all of the things what can happen to novice happened in row. 
Nearly runaway reaction, experiencing how much NO2 (and how quickly) is produced when 3 kg of mainly copper/zinc is dissolved in nitric  , filtering 8-10 liters of juice with fritted glass of 300 ml capacity..., not getting the clear liquid and going straight to cementation, settling the silver mud with flocculant for 2 days, ending up filtering it anyway, realize that this isn´t possible to filter in human lifetime, deciding to redissolve the mud with nitric, now experience runaway reaction  , clean it up, drop the silver as chloride with salt, nearly another runaway when doing lye/sugar method... And my first kilogram of silver was born. Also wishing I had experience to stop my younger self from doing it _


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## Yggdrasil (Jan 27, 2022)

Hehe, good to look back and cherish the memories of past follies.


Sometimes this little troll guy, named Murphy, just have to be sitting on your shoulder.
When things that you could swear never could happen in a million years, just happen three times in a row.
Unless that is what you want to happen, then it would take a million years.


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## Buckly (Feb 2, 2022)

ssharktu17 said:


> I have access to 55g chemical drums they are food grade used to hold acids for cleaning.
> 
> Also, as far as nitric acid everyone says 67-70% but what if I have access to 25% or 30% at a much lower cost? Are there impurities or is it just more dilute. Considering the first step in dissolving silver is diluting the acid 50% why not just start with 35%?


It depends what the grade of the 25-30% is. Should be fine (if good graded), just take longer...


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## Racoon (Feb 3, 2022)

ssharktu17 said:


> I have seen people running the reaction in 5g buckets so I thought it might be fine.
> 
> Any specific contaminants to watch out for? The drums are HDPE resin.


Using 55 gal. Drums seems to me over kill, unless you’re doing multiple pounds of silver at a time and even then you miss out on the enjoyment of seeing the reaction.


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## orvi (Feb 3, 2022)

Racoon said:


> Using 55 gal. Drums seems to me over kill, unless you’re doing multiple pounds of silver at a time and even then you miss out on the enjoyment of seeing the reaction.


Doing multiple pounds is exactly what was intended and started whole discussion.


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## kurtak (Feb 4, 2022)

Racoon said:


> Using 55 gal. Drums seems to me over kill, unless you’re doing multiple pounds of silver at a time and even then you miss out on the enjoyment of seeing the reaction.


As orvi pointed out - in this thread we are talking about working on a larger then hobby level - MUCH LARGER

Kurt


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