# Film silver recover,a new process



## Juan Manuel Arcos Frank

There are many processes for silver recovery from B/W films,offset negatives and radiographies.Combustion of film,nitric acid leaching,caustic soda leaching and CLOROX treatment have been proposed in this forum.Except combustion,all of them produce a silver intermediate compound that needs more processing to obtain pure silver,besides,all these processes release toxic fumes to the environment and nitric acid leaching and caustic soda leaching can cause severe burns.

The new process uses a low concentration of oxalic acid to attack the gelatine of the film and the silver goes down as a grey/black mud that only needs drying and melting to obtain pure silver.Concentrated oxalic acid is poisonous,please,use NIOSH/MSHA approved respirator,NIOSH approved gloves,splash goggles for eye protection and wear appropriate clothing to prevent skin exposure. Read MSDS for oxalic acid before start the process.

The process is quite simple,just make a 5%(weight or volumen) solution of oxalic acid in tap water,heat this solution to 95 C,then submerge the films in the acid solution,in 20 minutes all the silver is removed.Once that all silver has been removed rinse the films and let them dry,you can sell the plastic base to a plastic scrap dealer.

Let the mud settle down,pour off the liquid solution,dry the mud and melt it,you will get 0.999 silver.

Manuel


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## goldsilverpro

I'm always interested in a new way of processing film.

Several questions.

(1) Does silver oxalate form or, does *all* of the silver remain as silver metal? If silver oxalate does form, it is on every explosive compound list that I can find. I found one MSDS for a rust remover that was pure oxalic acid. It said that it would form silver oxalate on contact with silver. Silver oxalate doesn't seem to be extremely explosive, but it can be when confined or heated.

(2) How does oxalic acid react with silver bromide (on green film)? How does it react with silver bismuthate, which I think is the chemical found on the very common Dryview x-ray film? In the U.S., almost all lots of rare earth x-ray film contains some Dryview mixed with it. Will oxalic acid clean all the emulsion and silver off of Dryview film?

(3) 95C (203 F) is very hot. What type of vessel do you heat it in?

(4) What happens to the emulsion. Is it all converted to soluble amino acids by the oxalic (very doubtful) or, is it (even partially) included in the silver sludge? If it is included in the silver sludge, I cannot see how it could be practically be direct melted (after drying) without first incinerating it. 

(5) Does it completely remove the transparent mylar coating from the PET x-ray film? If not, the scrap value of the plastic is near zero. Also, if there are any black specks of silver from Dryview film mixed with the plastic, the plastic is worthless.

(6) What is the chemical cost to process a pound of x-ray film with oxalic acid? I would bet it's a lot more than caustic soda.

(7) Have you ever done this on anything greater than a lab scale? I consider 1000 pounds per day as still small scale. To make money, film refining is a high volume, low margin process. It requires lots of space, equipment, and labor. Can oxalic acid compete with caustic soda at a 50,000 pound per day level?



> Except combustion,all of them produce a silver intermediate compound that needs more processing to obtain pure silver,besides,all these processes release toxic fumes to the environment and nitric acid leaching and caustic soda leaching can cause severe burns.



*Not true!*

After stripping, neither caustic soda or enzymes/baking soda require more processing, except for incineration/melting. I believe the oxalic acid product will require the same.

Neither caustic soda or enzymes release toxic fumes.

At 200 F (the same as the oxalic process), only 3 to 4%. w/v, caustic soda is needed. I doubt that this strength is any more dangerous than 200 F oxalic acid - probably less. Oxalic acid is a strong organic acid. Are you saying that a 203 F solution of it won't cause burns?

I liked your battery info very much, but I don't like the oxalic process at all. I think it's a curiosity rather than a good production method. For an amateur to play with, it may be OK (if it doesn't form silver oxalate). As a serious production method, it seems to miss the mark, no matter what.

I look forward to your response on these points. 

Please don't take this personally. You're one of the best people on the forum, as far as knowledge and imagination go, and I'm sure you have other things up your sleeve. I'm a pessimist when it comes to processes. There are so, so many ways to skin a cat in this business. I always look at things from the "what's wrong with them" viewpoint. I've been surprised too many times in the last 40 years.

I learned to never live or die with a process, even if I were the one to invent it (very difficult to displace the ego). Going from lab quantities to production quantities is often very difficult and full of surprises. I would rather examine things negatively at the very beginning.


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## Juan Manuel Arcos Frank

GSP:

Oh My God!..a chance to discuss with you, a giant of this forum,well,let us do it but first of all I recognize the fact that you know more about silver recovery than I.

(1)
In low concentration oxalic acid does not dissolve the silver,silver always remains as silver metal.You are right about rust remover,but it is pure oxalic acid,using concentrated oxalic acid you could form silver oxalate,extremely explosive.

(2)
Oxalic acid attacks gelatine,not black silver in the film,the acid does not attack silver halide either,so if you have virgin films the silver halide will precipitate but I strongly suggest you to select developed films from virgin films,virgin films can be submerged in a common photo fixer and it is lovely recovering silver from these type of films.About silver bismuthate I know nothing about it.

(3)
Yes.Sir,95 C (203 F) is very hot but since I come from photofinishing bussines I use 316 stainless steel vessels from my obsolete machinery to heat the solution,to get 95 C I use a common direct fire device.

(4)
Gelatine is a protein,so the oxalic acid dissolves it by breaking down the cross link network of the gelatine,the gelatine gets flaky and covers the silver which comes down.The acid also dissolves aminoacids,fire´s torch will complete the job to get pure silver.

(5)
Yes,it does completely remove all components from the layer,you can get a clear film (X ray,offset negative or B/W negative).Many years ago,the clean film of a radiography values more than its silver content.Plastic scrap dealers will be happy when you sell to them the clean plastic films.

(6)
GSP,do not bet,you will lose because if you compare both processes oxalic process is cheaper than NaOH process just for a simple fact: NaOH process forms a black colloidal solution of silver which is impossible to filtrate and never will precipitate so you have got to break down the colloidal solution by heating,stirring and settling down for a couple of hours.Oxalic process just needs 20 minutes and pure silver is easy to precipitate.Here in Mexico NaOH costs 11 pesos a kilogram (almost 1 USD),oxalic acid costs 20 pesos a kilogram (almost 2 USD).

(7)
This new process will fit any load of films,I used to recovery silver with NaOH but I have changed to oxalic process because is cheaper and faster.This process can compete,and defeat,the other processes.


You are right about caustic soda/enzime processes,they do not release toxic fumes.

Of course,at 95 C anybody could burn but I mean chemical burns with nitric acid or NaOH.


GSP,here is a new and revolutionary process,let us meet the challenge,why do not you try it?,anyway if you do not like oxalic process you can still using NaOH process,but I am sure you will change to the oxalic process like a I have changed to oxalic process a few years ago.

Regards

Manuel


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## Lou

I am watching this intently. Oxalic acid is indeed more expensive than lye but I would far, far rather use hot oxalic acid--it is far more benign in my opinion. Also, oxalic acid is easy obtained from Univar or Brenntag by the 22kg sack.


From the chemist's standpoint--silver oxalate is something I would not bet on given the temperature of this reaction as it would thermodynamically unfavorable. Most explosives are made at low temperatures. Also, silver oxalate isn't terribly soluble, and as I recall it, it's made from soluble silver cation, not from solid silver which even colloidally dispersed ought to be inert to attack by oxalic acid of any concentration. What ought to happen isn't really good enough in my opinion when it comes to explosives. This process has me interested and I will probably conduct my own experiment in the laboratory with this. 

Of late, I am very, very wrapped up with the platinum group but I will concede that there is lots of silver out there in this world and *there exists a tremendous profit potential for recovering silver versus other precious metals*. It may be cheap as dirt in comparison to rhodium, but I will see thousands of ounces of silver for every ounce of rhodium.

I have revised my view on silver in the past few months, mainly due to my readings of Chris's work with it. I've never dabbled in chasing silver save for using it in other processes but I've friends that are doctors and/or professors that see and have thousands of pounds of x-ray film that they must pay to dispose of so I'm thinking to give it a go. I'm quite interested in how you both establish your supply of film and other silver materials--if I do this I would like to set it up to do it on a large scale. 

If you have a mind to, either of you contact me privately with your professional opinions on it. I'm willing to do quid pro quo on my ideas and practices regarding the platinum group.


Louis


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## Noxx

> there exists a tremendous profit potential for recovering silver versus other precious metals



I don't understand why... Is it because the volume evolved is much larger than other precious metals ? 

I've been interested in silver recovery/refining lately as well, I'm currently making photo grade silver nitrate.

Thanks for any inputs.


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## Lou

Exactly my point. I think across the board, it is much more easy to acquire huge quantities of silver at a good profit margin than gold or other PMs. It makes sense since there is more silver floating around as it is more common, and cheaper (therefore it's properties are fully exploited). 

That said, if you can make a dollar or two per ounce on silver and do several thousand ounces a day, you're doing (in my opinion mind you) quite well.


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## Harold_V

I considered silver refining nothing short of a nuisance (although interesting), but it's very much a part of refining gold-----it almost always comes with scrap karat gold, and becomes the carrier of platinum and palladium, so you don't really have any options. You must process silver, or lose some values to others. 

In a sense, I processed silver for my customers in exchange for their gold business. On rare occasion, I processed just silver, often from dental amalgam. It's a great source if you can get hooked up with a few dentists. 

Harold


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## goldsilverpro

First of all, let me apologize for, perhaps, making a judgment too early. I presently have no lab to test this process. So, let's assume that I was too hasty and let's start from scratch.



> I recognize the fact that you know more about silver recovery than I.


Don't sell yourself short. You know a lot more about using oxalic acid than I do.

(1) Even the very slightest possibility of forming silver oxalate would prevent me from using this process, especially since the caustic process works so well. I would have to absolutely know that the conditions would be such that it would be *impossible* to form silver oxalate. I find it difficult to think in anything but large quantities. Melting would be done in about 4000 oz quantities. If any silver oxalate were initially present, the results could be disastrous. Here's a guy that has played with this: It's not very good, but it's a start.
http://www.powerlabs.org/chemlabs/silver_oxalate.htm



> Concentrated oxalic acid is poisonous,please,use NIOSH/MSHA approved respirator,NIOSH approved gloves,splash goggles for eye protection and wear appropriate clothing to prevent skin exposure. Read MSDS for oxalic acid before start the process.


(2) Are you suggesting using the respirator when just mixing the chemicals or, also, when operating the process? I hate those damned respirators when running a process. I know they're not necessary when using weak caustic soda.

(3) Concerning the costs of a caustic soda operation. About 200 pounds of caustic will process 10,000 pounds of film. At about $.25 per pound of caustic, that is a chemical cost of $.005/pound of film. Also, the silver bromide on virgin film was easily converted to Ag2O. What is the chemical cost of oxalic acid, per pound of film? When running film, you have to count your pennies.

(4) Concerning the mylar problem. On certain x-ray films (I can't remember which - it may be only Dryview), a very thin film of transparent mylar is applied on one side of the PET plastic - you can't see it. If this is not removed, the scrap value of the plastic is nil. When selling it, it may take a while for the buyer to catch on, but contamination of mylar will come back to haunt you. Been there - done that.

After stripping everything off and rinsing and drying the plastic chips, the presence of mylar (and dirt, in general) can be tested as follows: Fill a small, shallow, heatable container (we used those standard disposable aluminum weighing dishes - they are about 1/2" deep and 2" to 3" in diameter) about 1/2 full with the clean plastic chips. Heat slowly on a hot plate until the plastic is completely melted (about 500 F). Don't overheat or you will burn the plastic. The melt should be a uniform blue (most of the plastic has a blue color - not all) with no evidence of black particles (mylar, silver bisuthate flakes, or dirt).



> NaOH process forms a black colloidal solution of silver which is impossible to filtrate and never will precipitate so you have got to break down the colloidal solution by heating,stirring and settling down for a couple of hours


(5) Who cares? That's not a problem, especially when running large quantities. Usually, the larger the volume, the longer it takes to fill the equipment "pipeline." We were running 50,000 to 80,000 pounds per day. A batch spent about 1-1/2 days in the system, from film to bullion. Our settling times fit easily into this timeframe.

(6) The medical x-ray film scrap industry is in chaos in the US. Dryview has made huge inroads. It is developed by heat instead of by chemicals. To test for Dryview, hold a lighter under a transparent area of a piece of film (the border, e.g.) - with Dryview, the heated spot will turn black. Also, purely digital x-ray equipment is becoming popular - the x-rays are viewed on a monitor - hard copies are only generated when desired. Regular rare earth film scrap is becoming rarer and rarer. In less developed countries, the expensive equipment needed for these other technologies makes their presence less probable - rare earth film is still widely used.

On the other hand, litho film scrap is still alive and kicking. When I ran film, litho made up about 35% of the total volume of all types of film. It comes in 2 thicknesses - 4 mil and 7 mil. About 98% of all litho film is 4 mil. Litho film (4 mil) contains about twice as much silver, per pound, as medical x-ray. 

(7) Is the gelatin *totally* dissolved? In my experience in working with other acids is that it never is totally dissolved. A pound of developed rare earth x-ray film only contains about 1/10 of an ounce of silver, on the average. That's about 1/3 of a cc. The bulk density of the silver powder would be a somewhat less. How much volume of stuff do you get from a pound of film? I repeat - with any residue of emulsion, the sludge will have to be incinerated before it is melted. I am talking about when running large amounts of film. It is a matter of the capacity of the furnaces and of the needed control of the horrible fumes produced when burning the emulsion. It's easier and cheaper to control this with incineration than it is with melting, Also, the carbonaceous emulsion provides a voluminous, variable, additional fuel, which is difficult to deal with in a melt.



> *there exists a tremendous profit potential for recovering silver versus other precious metals*


I totally agree, Lou. The last time I looked, there was as much silver scrap out there as gold scrap, dollar-wise. Also, there are probably 50 times more gold refiners than silver refiners. I love silver. Not because of its beauty, but because it paid the bills for a big part of my life. If someone wants to start another thread, we can discuss this in more detail.


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## Noxx

Ya I'll start another thread in the Silver section.


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## qst42know

Being quite intrigued by this process I dug up some early photo negatives. I don't know what kind of matierial they are made of but roughlly from the 1920s 3x5 single photos and perhaps celuloid not mylar. I don't have access to any xray films.
This test is by no means scientific I know but,
In a nalgene 400ml beaker I brought tap water to a boil added 1 rounded teaspoon of oxalic acid wood bleach. I wrinkled the films so they wouldn't stick together like an old wet book. Within about 2 min. the coatings begain falling off in gobs like dead skin. Within about a half hour and one additional heating in the microwave and ocasional stirring the films were clean. 
I have not processed the solution as yet.
I'm impressed by this little test as it is quick and simple. There may be other issues to address such as filtration. I just wonder what someone could accomplish with an old washing machine in a days time.


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## goldsilverpro

To, me, the question is not whether that oxalic acid will strip it (actually, about anything will strip it - I read once that someone stripped it with very hot water). The question is whether, or not, it would work well and make money in a production situation.

Be careful with that 1920s film. It is very flammable nitrate film and, under the right conditions, it can be explosive.


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## qst42know

I haven't gone any further with this yet. But if the oxalic breaks down the gelatin and the filtration isn't to much of a problem. This may be worth some scale experiments. Does lye or bleach digest the gelatin? 
Good tip on the flamable film. A thin strip of it burns like smokeless gun powder.


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## qst42know

Modern films may be a far more valid test as it would be no easy task rounding up tons of 20s film. I'll see if I can scrounge up some xrays and try again.


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## Chuck_Revised

Unfortunately, litho film has fallen by the wayside in the developed countries. Newer processes skip the film step to directly produce a metal/polyester plate for printing or utilize inkjet technology in what's known as digital printing.

I am the owner/operator of the remainder of a typesetting/service bureau company. Search the forum for "imagesetter" and you'll find how I disposed of one of my litho film generating machines--dismantled and sold mainly for parts plus some scrap recovery.

In western Europe and North America, litho film usage is primarily in mom-and-pop shops and certain specialty shops. In 3-5 years, it'll probably be history, like the Linotype.

Still used somewhat in the underdeveloped countries.


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## Juan Manuel Arcos Frank

Lou:

Gold and PGM recovering are exactly like marriage:If you are in marriage you want to get out,if you are out of marriage you want to get in.People in gold and PGM recovering want to get out to silver recovering,people that ,we,are in silver recovering want to get in to gold and PGM recovering... It is OK,let us feedback ourselves because we are modern alchemists so we have got to recover all types of precious metals.

You can get used films in three places:

Hospitals (as used radiographies or out of date virgin films).

Newspapers(as used films).

Industrial X ray (as used radiographies or damaged virgin films)

Of course,you can get the spent fixer of these processes too.

I am glad that you are going to experiment the oxalic process,the silver film recovery is a good bussines,welcome to the silver recovery bussines.

Lou,it is my pleasure talking with you.

Best Regards

Manuel


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## Juan Manuel Arcos Frank

Noxx:

It is simple:there are more silver than gold or PGM.When Pachuca´s mines were working the ores contained 300 gr/ton of silver,1.5 gr/ton of gold but silver´s price went down for many years.Recently silver´s price increases due to industrial silver´s uses,so silver recovering become a good bussines.

Have a nice day.

Manuel


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## Juan Manuel Arcos Frank

Harold_V:

Rough and wise,as always.How about recovering more silver than gold?.I am sure you will get too much money from silver recovering.

Regards.

Manuel


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## Juan Manuel Arcos Frank

GSP:

You have nothing for wich apologize,but you are hard to convince,I will answer all your questions and will make you a proposal.

(1)
This guy uses silver nitrate,of course,will form silver oxalate.Metal silver only reacts with concentrated oxalic acid.You will never use concentrated oxalic acid to recover silver from films

(2)
GSP,WE ALL HATE those damned respirators,but you just need it to handle concentrated oxalic acid and to prepare the weak solution,you do not need the mask for running the process.

(3)
Let us count our pennies:Oxalic acid is more expensive than caustic sosa,but weak oxalic acid solution could be reused many times,so the cost goes down,besides,oxalic process is faster than NaOH process,this also goes down cost processing.

(4)
Oxalic and NaOH processes are silver recovery ones,the waste plastic film,in both,could be sell to srcap plastic dealers,they have to recover the plastic,they know what to do,that is their bussines.I provide you a method for recycling the plastic base of films.

(5)
GSP,colloidal solutions are our enemies,they are a nightmare and we have got to avoid them because they never precipitate.Running 50000 or 80000 pounds with oxalic acid process will spend 12 hours from film to bullion.

(6)
We have got to hurry up,film technologies are getting obsolete,digital X ray equipment and CTP technologies point a gun in the middle of our eyes,but there is still a potential because radiographies must be filed for 10 years.

Look,GSP,I propose you to forget all what we have said,take some films and take a half and process them with NaOH,at the same time take the other half and process them with oxalic acid,you will see the difference.

Do not make the same mistake that we,mexicans,do:we have bricks to contruct a wall but...we try to construct a pyramid!,the result is that we do not construct the wall...neither the pyramid..so I strongly suggest you to construct the wall first,then construct the pyramid and I am sure you will construct a very hig building.Do not worry about the pounds of film you 
have,this process works well even you have 1,100,1000 or 100000 pounds of film.

Regards

Manuel


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## Juan Manuel Arcos Frank

HERE IS THE LINK TO THE PLASTIC FILM RECOVERY ARTICLE

http://www.wipo.int/pctdb/en/wo.jsp?wo=1993001525&IA=WO1993001525&DISPLAY=DESC


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## Juan Manuel Arcos Frank

gst42know:

BRAVO!!!...you did it!!,just poor off,dry and melt.Please,if you can, post a pic of you silver.

Congratulations!!

Manuel


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## Harold_V

Juan Manuel Arcos Frank said:


> Harold_V:
> 
> Rough and wise,as always.How about recovering more silver than gold?.I am sure you will get too much money from silver recovering.
> 
> Regards.
> 
> Manuel



Manuel,

Funny, my customer base was established by need. I don't know if I was lucky, or it's the nature of the business, but silver came to me in about the proper ratio that allowed for inquartation of karat gold. I rarely ran out--but I made a point of not processing silver scrap without first using it as my added metal. I'm not sure I could have increased my flow ---although at one point in time I'd have gladly done so. You may understand that I no longer refine, having sold the business in the early 90's. 

Unlike GSP, I ran silver on a limited basis. My cell was small in the scheme of things, so my output was not large. I would accumulate a couple thousand ounces before firing up the cell, then it would run on a continual basis until I had processed all of the anodes I had cast. 

Melting once recovered silver for reuse in inquartation, for me, was not a good idea. It typically had platinum or palladium, often both, included. Allowing those metals to get too highly concentrated raises hell in the parting process---often leading to depleted electrolyte (been there, done that, caused by a heavy coating of platinum and palladium sponge that restricted free flow of silver from the anode). 

I am of the opinion there's a lot of money to be made with silver----it's just that I had better success with gold.  

Harold


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## Oz

That is a very interesting commentary Harold. I have been re-running the same silver for some time for inquartation with gold knowing full well that I was accumulating PGMs. I have yet to build a silver cell to clean my “impurities” from it. It is good to know that the high PGM content may cause problems if I understand you correctly. Oddly enough it seems that I may need to dilute my inquartation silver with additional silver when I get to the point of wanting to remove reasonably pure silver, based on your comments. 

As stated above, I have no personal experience yet with a silver parting cell.


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## Harold_V

When I ran my wastes, after more than 20 years of operation, the yield was very high in the platinum group, due to my including the stock pot residues in the waste material. I learned to not try to recover from dilute solutions after recovering gold---the values were recovered in the stock pot. 
Parting the silveranodes (the silver was recovered with copper) was a real trial. I had to hand scrape the anode to free the sludge, and it didn't go willingly. It normally sloughs off and can be scooped out, using an acid dipper. 

So this makes more sense, I had included all my filters from filtering gold chloride solutions, each of which had a generous amount of silver chloride included. That was by design, knowing it would act as a collector when I processed the waste by furnace. I didn't want to use lead----for obvious reasons. 

As it turned out, the plan worked exceedingly well (more by sheer luck than anything, although I did my homework regards using what I thought was the proper flux). In the recovery process, parting the doré that came from the furnace allowed for some separation of platinum and palladium from the solids, but not all. Remember, when platinum is in the presence of silver, some of it, if not all, will dissolve in nitric acid. 

I strongly advise you not endlessly use the same silver to avoid problems later. I also advise you to check the nitrate solution after the silver has been precipitated with copper, especially if the solution is NOT blue. My experience indicated that if it leaned green, it was because the solution contained values. They are generally the last to come down, and appear as black smut in the silver. Test your solution, ALWAYS, with stannous chloride. 

Harold


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## Oz

The silver I re-use is indeed recovered with copper cementation as you did. I also knew that palladium and platinum hitched a ride, I am not as sure about the occasional rhodium.

I also agree that any silver that survived inquartation then nitric would be in my saved filters.

I have not bothered to do serious research into the flux I would require as I only have several gallon containers of filter material saved as of yet.

The most informative point to me was the difficulty you had in parting the silver if PGMs were high. It is your experience that leads me to believe I needed to part my silver sooner than later.

Cementing my silver I always get that deep cobalt blue due to patience, but you are correct in stating I should check more often than I do with stannous.


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## Harold_V

If you have the ability to incinerate, do so. Filters will burn down to very little ash, making storage easier, but most importantly, free from acid fumes. I heated mine until all the carbon had been eliminated. You can verify that by playing oxygen on the ash, using a torch. If any carbon remains, it generally burns with a brilliant yellow/white intensity. 

If, when you're ready to melt your waste materials, I'd be happy to provide the flux recipe I used. Fact is, I think I've posted it on the board before. 

I had my slag assayed after recovery and found it so low in value that the company in Sparks, Nevada (now defunct) that used to process just such things for contained values, wouldn't accept it. I ran my waste in a reverberatory furnace of my own design, and it got a generous soak, insuring all the values were collected. I explored all of the slag as I cleaned the buttons and never found prills. The slag was very fluid----and reduced the values beyond my wildest hopes. It was correspondingly hard on furnace lining, but that's a small price to pay when recovering over 200 ounces of gold, to say nothing of the silver and platinum group. 

Harold


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## Oz

It looks like we are the insomniacs in the US tonight, perhaps we should have taken it to PMs. I hope there is value to others in our multi-thread chat.

I have read your post on incineration and think somewhere on my computer I have saved your flux recipe. I have a $1 stainless steel pan that was a flea market find waiting for the day I need to reduce my filter volume. As I have a torch, it is a nice idea you have applying oxygen to the ash to assure complete combustion of the carbon as it can steal values.

Some of my delay in filter processing is in fact due to you and your mention of your “savings plan”. Small amounts compared to what has been processed to be sure, but it will work like compounded interest.


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## Harold_V

Oz said:


> It looks like we are the insomniacs in the US tonight, perhaps we should have taken it to PMs. I hope there is value to others in our multi-thread chat.


I am, by nature, a night person. I generally get to sleep around 5:00 AM, and sleep until about 11:00. I followed that schedule for many of my working years. I'm far more productive if I don't get up early. 

As far as others are concerned, if they can't learn anything from our conversation, I pity them. There are all kinds of subtle tidbits that are being tossed about here. 



> As I have a torch, it is a nice idea you have applying oxygen to the ash to assure complete combustion of the carbon as it can steal values.


I congratulate you for knowing that. I wonder how many do?

Yes, my ash was barren of carbon. Always. I heated my pan with natural gas until all the things that would burn did, then I heated the pan with my Hoke torch until the base was red. Any carbon that had not burned readily did so. I also stirred the waste with a steel rod, 3/8" diameter, to insure that everything was exposed to oxygen. 

While the above took time, my reward, in the end, made the time and money spent through the years to appear as a bargain. It truly was. 



> Some of my delay in filter processing is in fact due to you and your mention of your “savings plan”. Small amounts compared to what has been processed to be sure, but it will work like compounded interest.


Yep! You can't spend it when it's just junk. 

I had retirement in mind from the outset------that's what my gold was intended for. Turns out I saved a lot more than I realized, thanks to the waste materials. Best part of the entire thing is I had a lot of fun along the way, and learned so many things that I, otherwise, would not have learned. One of them is how little people know about gold. 

Harold


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## qst42know

Manuel, 

I up sized the batch to 5oz of film. The solution is fast through the filter the gelatin must be gone. Too fast for coffee filters. The silver on film must be very fine. 

I am tracking down some better filters What grade would you suggest? 

Some material settled quickly however the solution is still quite dark. After sitting for a couple of days the solution seems to be clearing the more it sits. 

Because of the dark solution how do you know when all the silver is down?


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## Juan Manuel Arcos Frank

gst42know:

Use filter paper No. 2,it is the standard and it will work well.Almost all the silver is down,but filter the solution,darkness could not be silver,could be aminoacids,do not worry,all your silver has benn precipitated.

Regards

Manuel


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## qst42know

I ended up making some nitric and adding some to this solution in a couple test tubes. When the solution went clear a pinch of salt in one and a couple drops of hcl in the other with no reaction in either.

Just waiting for the filter funnel and papers to arrive.


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## Juan Manuel Arcos Frank

gst42know:

It is OK,I am here to see what happens.

Regards.

Manuel


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## qst42know

It took a while to but after running this through a vacuum filter with #5 Whatman filter papers (2.5um) I was only able to capture some of the silver. Much of it is so fine it passes right through the filter. If you were to use #2 filters most of the silver would be lost. The remaining solution was set aside to settle, then the bulk of the liquid was siphoned off. I plan to evaporate the remains.

If this were attempted on a commercial level how would one collect this material that so stubbornly defies filtration?

I will get back to you with my results.


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## eagle2

No doubt the expert refiners here would have a good method. 

But you don`t have to filter. I would just suction off the liquid after the solids settle. Wash them with water once or twice, letting the solids settle each time. Suctioning off the liquid one last time and evaporating the last, until it is dry enough to melt to a dore` bar. 


Then sell it or electo-refine it yourself.

Al


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## Lou

Try boiling it. Sometimes a good boil helps precipitates agglomerate and stick together.


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## qst42know

I tried to vacuum filter and the finest standard grade of Whatman filters was no match for this solution. In an effort to keep the waste solutions down I will give boiling a try. Its half way to evaporation anyway.


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## qst42know

This solution was indeed stubborn. It took a boil, settle, change water, boil and settle. Boiling and rinsing. So thanks to both Lou and eagle2. I suspect a separatory funnel may have been beneficial but I don't own one.

After much fretting and fussing the results from approximately 5-1/4oz. of this early film negatives I recovered 1.25 gm of silver. The larger ball is 1 gram and is from the first filtering of the original solution and the water I rinsed the negatives in. The second bead was from the fines that gave me such trouble and weighs 1/4 gram.

The amounts are trivial I know but this was a quest for knowledge. And this was indeed a learning experience. Thanks for all the advice and help.

A couple of the big lessons: film silver is very fine a couple days of settling makes a difference. Oxalic acid seams to have a soap like quality that keeps things in suspension. Boiling and rinsing is vital. Continuous agitation and perhaps shreading would help keep films from sticking together. The silver is very clean as evidenced by the sprouting (the surface eroptions) of the first button.

Chris


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## Juan Manuel Arcos Frank

qst42know:

Congratulations!


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## hoardpm

If I am reading this correctly if I use oxalic acid to process films there is no need to pracipitate the solution. Just let settle, syphon off the liquid then let dry and melt. Is this correct? What about the gelitan or other contanimantes that are on the films? Also, in the event that silver oxalate if formed as GSP suggests is there a way to test for it other than throwing a torch to it and hoping I dont blow up?


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## qst42know

This is the procedure I found for forming silver oxalate.

http://www.powerlabs.org/chemlabs/silver_oxalate.htm

It is synthesized from silver nitrate.

If you keep nitric acid out of the mix you should be OK.

Does this sound right to you Lou? GSP?

Developed film doesn't have any silver nitrate remaining does it?


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## Lou

Yes, it is made from silver nitrate. It's nothing much to worry about.


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## Juan Manuel Arcos Frank

Hoardpm:

Yes,Sir...this is all what you have to do...no colloids,no gelatine,nothing of nothing except pure silver...from my experience 1 kg. of normal radiographies have 12.8 gr. of silver....1 kg. of offset negatives from newspapers has 10.2 gr. of silver....Good luck.

Manuel


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## goldsilverpro

Juan said:


> from my experience 1 kg. of normal radiographies have 12.8 gr. of silver....1 kg. of offset negatives from newspapers has 10.2 gr. of silver



From my experience (50,000,000 pounds of film processed and 6,000 assays done on this film - from about 2000 to 2004 - I did these assays and the actual yields proved them), your figure for average radiographies is way too high, by about double. 

In the U.S., the average figure for developed rare earth x-ray film (the standard type film used in the U.S. since 1985) is very close to 0.1 tr.oz./pound (6.8 gm/kg). This average figure is absolutely set in stone. I've seen it run from 4.1 gm/kg to 9.6 gm/kg, depending on how black it is.

Undeveloped (green) rare earth film does run about 12.4 gm/kg, but it makes up a very small percentage of the scrap film available.

Developed NMX (a trade name), the film used prior to 1985, did run about 11.6 gm/kg. Maybe they're still using that in Mexico.

Average newspaper litho film does run about 10.2 gm/kg, as you said, but it can run from 0 to about 17.7 gm/kg, depending on the percentage of black covering the film.


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## hoardpm

well this process has got my curiosity going. My sister-inlaw is a radioligist. She had stated that the "owner" of the clinic was looking to avoid the cost of disposing of the films and such. So I told her to I would take the stuff free of charge. Her boss wants to talk to me about how I'm going to go about destroying the films and such. But, I that brings a whole new problem because there are paitent privacy laws which require "proof of distruction" if the films are given to another party to dispose of. Not sure how to go about accomplishing that task. I am willing to bet the clinic she works at will spend the money to switch to a totally digital X-ray process. In the event of that happening. Are there any other sources of silver from film I could explore and how would I know where to start looking?


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## Oz

For destruction of the films just use a paper shredder, that should also leave you a material that would be easier to keep in intimate contact with your solutions.


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## goldsilverpro

Besides having to destroy the film, if you don't cut the film up in some way, the full sheets will stick together and it will take forever (many hours, in some cases - sometimes, the full sheets never completely strip) for the solution to penetrate between the sheets, even with tumbling. When the emulsion gets wet, it gets sticky. You can run the sheets one at a time but, of course, that's a very slow process.

Occasionally, we received film that had once gotten wet and then had dried. The sheets were permanently glued together, some in 20 pound chunks that were way too thick to run through the chopper. When you tried to pull the sheets apart, they tore. The only way to process it was incineration, which can lose as much as 30% of the silver in the smoke. 

A paper shredder works but it twists the pieces badly and this gives the material a very low bulk density. In other words, very little weight of material will fit into a given container. Hammer mills do the same thing. Equipment that actual cuts (chops or shears) the film into small flat pieces works much better, but it is expensive.

We chopped the film into about 3/8" pieces and put it into 40 gal fiber drums, which held about 65 pounds of this material. Occasionally, someone would send in material that that had been run through a hammer mill or a paper shredder. The drums would only hold about 10 pounds of this material. Therefore, in a given sized container, you can run about 6 times more production with chopped film than you can with film run though a paper shredder.


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## Juan Manuel Arcos Frank

GSP,my good Friend:

Sorry...I was not in my town that is what I am late.

I call "common radiographies" radiographies made in an X ray gabinet or a hospital,with exposure index of 50% ( I mean,50% of the film is black).News paper negatives have a 70% exposure index.Of course,silver content varies widely.If I can manage the server I will post a pic of the silver nugget I got.

Have a nice day.

Your friend
Manuel


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## Juan Manuel Arcos Frank

Hoardpm:

Here is a trick.. you have to pellet your films... I do not the name in USA (here in Mexico it is called "peletizadora"= pellet machine).but people who recover PET bottles have this kind of machinery..so turn your films into pellets and you can handle many kilograms of radiographies for the oxalic process.Here,in Mexico,PET´s guys charge 1 peso (0.074 USD) to turn 1 kg of radiographies into pellets.

Complete films can be recovered with an out of date X ray processor,you just need to modify the heating system to acheive 95 C which is the process temperature.

You can also do it manually,get an used stainless steel tank( because a new one is very expensive),a direct fire device to heat the solution,put the films into the solution,heat them and you will get the silver...easy and fast.Recently I assisted a community in Honduras with this process,now they are processing 500 kg radiographies/day,I am sure you can do it too.

Regards.

Manuel


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## qst42know

I have a question. 

Has anyone recovered silver from old home movies? Those 8mm cameras used to be quite popular. That and other films.


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## goldsilverpro

If they are color, there is no silver on them. With color, all the silver dissolves into the chemistry.


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## Juan Manuel Arcos Frank

Yes,GSP is right,color films do not have silver.B/W films contain silver,they are very old films and if you find them be careful to trasport them because they can start a fire that you can not ever stop...in fact you have to trasport them submerged in water.

Mexico´s film archive was lost in the fire of 24/March/1982.Nobody could stop the fire.

Regards

Manuel


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## goldsilverpro

I have never seen nitrate film. Here's a good site that tells about the dangers of it and how to detect nitrate film.
http://www.movieeditor.com/2005/nitrate.fire.html

As I understand it, nitrate film was only made in 35 mm and 17.5 mm (35 mm split in half) and they stopped making it in 1952. The motion picture industry was the biggest user of it.

It was generally replaced by "safety film", made from cellulose acetate. Acetate film smells like vinegar. When it ages, it can get very crumbly.


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## qst42know

From the link GSP provided they will not spontaneously ignite. So transporting them in water should not be absolutely necessary. However the film negatives that I had, once cleaned of silver were very eager to burn. One at a time would disappear in an instant. Ten at a time in the same instant. Trapping them in a film can would likely accelerate them. They burned almost identical to smokeless gun powder, no residue and big flames. It didn't require a flame to ignite just a touch from a cigarette brushed lightly on an edge. Wicked stuff. A room full would be extremely dangerous, a building full downright explosive.


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## golddie

Hi Gsp

I could not see anything from this link


http://www.movieeditor.com/2005/nitrate.fire.html


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## goldsilverpro

They must have removed the link. Just search for something like - "nitrate film" dangers - in Google


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## Harold_V

qst42know said:


> However the film negatives that I had, once cleaned of silver were very eager to burn. One at a time would disappear in an instant. Ten at a time in the same instant. Trapping them in a film can would likely accelerate them. They burned almost identical to smokeless gun powder, no residue and big flames.


Many of the very early wire frame eye glasses used a plastic that burned equally as fast. Sure was easy to eliminate the plastic.

Harold


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