Can I use large chemical drums for dissolving?

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ssharktu17

Well-known member
Joined
Dec 10, 2021
Messages
113
Location
La
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'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
 
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...
 
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...
Click to expand...
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.

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

Dave
Click to expand...
Any specific contaminants to watch out for? The drums are HDPE resin.
 
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 ;)
 
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.
Click to expand...
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
 
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
Click to expand...
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.
 
ssharktu17 said:
Hey that’s not too bad! And stainless is fine it won’t contaminate at all?
Click to expand...

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.
Click to expand...

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

https://www.vevor.com/products/180q...l-stock-pot-w-lid?_pos=8&_sid=3a89f14f2&_ss=r
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
 
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

https://goldrefiningforum.com/threads/dissolving-the-copper-in-sterling-nitric-qty.29286/
https://goldrefiningforum.com/threa...ric-reasonably-cheap.30430/page-2#post-318763
Kurt
 
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)

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



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

https://www.vevor.com/products/180q...l-stock-pot-w-lid?_pos=8&_sid=3a89f14f2&_ss=r
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
Click to expand...
Thank you! What is the purpose of the steel plate on top of the turkey fryer?
 
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.
 
ssharktu17 said:
Hey that’s not too bad! And stainless is fine it won’t contaminate at all?
Click to expand...
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.
 
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.
Click to expand...
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)

https://www.harborfreight.com/stainless-steel-stock-pot-set-4-pc-60624.html
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
 
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.

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.
Click to expand...

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
 
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)

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
Click to expand...
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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