Silver scrap - film

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When I first joined the forum I found the search function less than helpful. The more you read, the more you will learn the keywords that will help you find what you seek.

I hope you keep some calcium gluconate gel on hand at all times. Hydrofluoric acid is indeed some horrifying stuff. I can't imagine anything I'd need to do in my yard that would be worth exposing myself to its dangers.

The first rule here is to be safe in everything you do.

Dave
 
Hi Dave,

the HFA is for removing enamel. Not something I use on a daily basis thank heavens and I tend to save up all enamel stripping I need to do so I can do it in bulk once or twice a year. I keep powdered lime to hand in case of accidents although I have a kind of outdoor double gloved chamber thing I do it in plus respirator.

I try to use minimal amounts of acid of any kind and have switched from nitric acid to Ferric Nitrate for etching because it's rather less scary.

chemistry was never my strong point, but hopefully I'll manage to get something out of all this fix.

I'll do some small tests comparing the zinc and wire wool methods.
 
M,

You obviously have more experience using HF than I. I haven't touched the stuff since I was a chemistry aid in high school. But I don't believe powdered lime is a substitute for calcium gluconate. HF passes through the skin quite quickly. If you're going to keep HF around, you MUST keep some calcium gluconate gel on hand.

Starting with some small tests on your fixer is definitely the way to go. Find what works for you, then scale up a little at a time.

Stay safe,

Dave
 
Hi Goldsilverpro, thank you for your effort sharing all your info and experience with us, particular those newbies.

I have a question please. What is the best method to recover silver from some kind of Ag/AgCl electrode. This kind of electrode is made of very thin layer of Ag and AgCl on plastic film, i.e. Ag on the film, AgCl on the Ag. The electrode is very small, 16mm x 6mm. From one side it can see shining silver color, from the other side, half is the shining and the other half color likes unused photographic film (brown). I guess the silver density is pretty high.

Is it the method NaOH+Sugar the better one for starter? Or maybe only NaOH alone plus heat? Well, for a newbie, can you teach me what equipment should I own to start? Thank you.

BTW, I can send you some of the electrode see how much silver you can get out of it! 8)
 
ayu said:
Hi Goldsilverpro, thank you for your effort sharing all your info and experience with us, particular those newbies.

I have a question please. What is the best method to recover silver from some kind of Ag/AgCl electrode. This kind of electrode is made of very thin layer of Ag and AgCl on plastic film, i.e. Ag on the film, AgCl on the Ag. The electrode is very small, 16mm x 6mm. From one side it can see shining silver color, from the other side, half is the shining and the other half color likes unused photographic film (brown). I guess the silver density is pretty high.

Is it the method NaOH+Sugar the better one for starter? Or maybe only NaOH alone plus heat? Well, for a newbie, can you teach me what equipment should I own to start? Thank you.

BTW, I can send you some of the electrode see how much silver you can get out of it! 8)

Assuming the electrode is composed of only Ag and AgCl, I would probably dissolve the Ag in 50/50 HNO3, precipitate AgCl with HCl, and convert all to Ag with Karo syrup and NaOH.
 
Thank GSP for your reply. I don't think HNO3 is cheat from the market, so does bleach (HClO) react with Ag to obtain AgCl? I believe Ag can't even react with high concentrate HCl alone. Since there is free Ag already, can I just use NaOH only to deal with the AgCl? Hm, but how to strip Ag off the plastic film? Can I burn the electrode film to get the free Ag first then deal with the AgCl?

GSP, can I send some to you per the address you mention on your e-book purchase post? For sure, when I start my hobby I will buy your ebook. That would be a short cut to me to search and learn... :lol: If you have time do you mind helping me to find out how much Ag can be recovered per electrode? Thank you in advance.
 
That would be a short cut to me to search and learn... :lol: If you have time do you mind helping me to find out how much Ag can be recovered per electrode? Thank you in advance.[/quote]

You will find that shortcuts are fiercely frowned upon on the forum.
if you want to learn,then you should start by learning the necessary safety first.
safety is paramount.you would not tell your child to cross the street,without first teaching him how.
then read hoke,as Harold said until you understand.
then use the search to gain the understanding you did not get from hoke.
then ask an educated question.
it has been pointed out that if you just go about asking newby questions on the forum,that you want to be spoon fed and that will now get you banned from the forum.
SAFETY FIRST you can fix a mess,but not a lung.
john
 
From where and what makes you think i am not concerned with safety? Nothing wrong with 'search and learn', is it?
 
ayu said:
Thank GSP for your reply. I don't think HNO3 is cheat from the market, so does bleach (HClO) react with Ag to obtain AgCl? I believe Ag can't even react with high concentrate HCl alone. Since there is free Ag already, can I just use NaOH only to deal with the AgCl? Hm, but how to strip Ag off the plastic film? Can I burn the electrode film to get the free Ag first then deal with the AgCl?

GSP, can I send some to you per the address you mention on your e-book purchase post? For sure, when I start my hobby I will buy your ebook. That would be a short cut to me to search and learn... :lol: If you have time do you mind helping me to find out how much Ag can be recovered per electrode? Thank you in advance.

I have seen a patent that uses bleach to strip used x-ray film. But it dissolves the gelatin emulsion and allows the Ag salts to drop to the bottom of the stripping solution. Not sure that would work on your material. (And it seems the bleach is used up quickly in the process.)
 
thank you all. I have tried to boil with water but Ag/AgCl layers do not peel off. I add some HCl then they do. I collect and dry them up, plan to burn them and see what remains.
 
ayu,

Do you have pictures of the electrodes?

I do not know what you have, but maybe I can give you some things to think about.

silver chloride if heated can decompose to silver and chlorine, But the silver chlorides can also be volatile so you can burn off your silver in the white smoke, so normally we do not want to try and melt silver chloride, we normally change it back to silver metal before melting using one of the conversion methods, like NaOH and karo syrup, HCl and aluminum or dilute H2SO4 and iron, another way is to convert it (or reduce it) to silver in the melt using sodium carbonate in the flux.

Silver will dissolve in dilute nitric acid, silver chloride will not dissolve in nitric acid.

Silver nitrate can be precipitated with HCl to form insoluble silver chloride (leaving nitric acid as the byproduct, if excess HCl used it would form a type of aqua regia, leaving some chloride in solution).

NaCl will also precipitate silver from a silver nitrate solution, leaving sodium nitrate as the byproduct.

Both of the above methods produce silver chloride which needs conversion back to metal before melting as described above.

Copper will cement silver from a silver nitrate solution, or replace the silver in solution, this gives us a powdered silver metal that can be washed and melted without much trouble or loss (the byproduct would be copper nitrate solution).

Silver chloride can be dissolved in a thiosulfate solution, it can be cemented out of solution with steel wool, or electrolysis used to recover silver.

Silver chloride will also dissolve in an ammonia solution, if doing this you should acidify the solution to precipitate the silver from solution and make it safer, as the silver ammonium complex can be dangerous if dried.

Silver metal will not dissolve in thiosulfate or ammonia.


It sounds like you have the silver/ silver chloride separated from the plastic, but at this point you still have a good portion of your silver as a chloride, melting it at this point you could burn off a good portion of your silver as white smoke, to prevent loss of your silver you should to convert the silver chloride to silver metal before the melt, or use a flux with sodium carbonate Na2CO3 also called soda ash, or washing soda, in the flux melt to convert the silver chloride to silver during the melting process.

Edit to add thoughts.
Silver chloride AgCl does not dissolve in HCl (although with high concentration and heat you may put a tiny bit into solution as AgCl2, dilution will precipitate it out of solution, my thought here is that with using HCl to remove the Ag/AgCl form the plastic you could still have chucks of silver chloride (which could be a bit more difficult to convert to silver metal by the normal conversion methods that we normally use on powders, where exposure to each grain of the salt is needed).
 
Hey butcher, appreciate all your time and your writing details about AgCl. I know I should search and learn more from the forum. Though I took chemistry (and quantitative chem) at school long time ago, for the specific case in melting metal it will be my first time. I have to get my hand dirty first before I can get any sense from all theories and other people's experiences.

Sure I will upload a picture how my stuff looks like later. As I don't have quantitative lab setup, so I have no way to find out what's the ratio of Ag/AgCl on the film. If their thickness is the same, the ratio will be 2:1.

According to wiki, melting and boiling point for AgCl is 455C and 1547C; while for Ag is 962C and 2162C. When using a propane/Map-Pro torch, I assume when they are heated to above 1547C but below 2162C (i think it is hard to control temperature), AgCl will be completely vaporized. I believe liquid Ag can be vaporized too during AgCl boiling, just assume and hope the amount can be minimized before the boiling point 2162C. My plan is to do a direct melting and a wet method too. Find out what different mass is between them.

Will update here. Thank all advices from you guys.
 
butcher said:
silver chloride if heated can decompose to silver and chlorine
I know there are websites that make this claim, but it's not true. I don't want to give anyone the false impression that all they have to do to decompose AgCl to Ag metal is to heat it - it won't work. In the CRC Handbook, it gives the boiling point of AgCl as 1550C. If it were going to decompose before that temperature, the CRC would have surely said so. I also read that someone in an old mining book on Google had experimented and concluded that AgCl will start vaporizing at about 600C (1112F). When you put a torch on AgCl, the copious white smoke coming off is AgCl. I have seen many incompetent melts that started off with just borax, silver powder, and some unconverted AgCl. Most were heated to at least 2000F (1093C). After being poured and cooled, there was always an intermediate unconverted AgCl layer between the flux and the silver bar (some AgCl had surely vaporized, though). To me, this proves that AgCl doesn't decompose with heat. It will melt at about 455C and then start vaporizing at about 600C.
 
goldsilverpro said:
butcher said:
silver chloride if heated can decompose to silver and chlorine
I know there are websites that make this claim, but it's not true. I don't want to give anyone the false impression that all they have to do to decompose AgCl to Ag metal is to heat it - it won't work. In the CRC Handbook, it gives the boiling point of AgCl as 1550C. If it were going to decompose before that temperature, the CRC would have surely said so. I also read that someone in an old mining book on Google had experimented and concluded that AgCl will start vaporizing at about 600C (1112F). When you put a torch on AgCl, the copious white smoke coming off is AgCl. I have seen many incompetent melts that started off with just borax, silver powder, and some unconverted AgCl. Most were heated to at least 2000F (1093C). After being poured and cooled, there was always an intermediate unconverted AgCl layer between the flux and the silver bar (some AgCl had surely vaporized, though). To me, this proves that AgCl doesn't decompose with heat. It will melt at about 455C and then start vaporizing at about 600C.

So if i'm correct from the information written above AgCl doesn't decompose at the temperature of "550°C", So incineration would have no effect on AgCl?

How should we recover the Ag from AgCl? using the ammonium method?
 
GSP,
Thank You for clarifying that point, that we cannot decompose the silver chloride to silver and chlorine by heating, I have read that statement several places, but never could find details of temperature or conditions that it might happen, I also never considered it as a replacement method to reduce silver chloride back to silver metal as we do in our recovery or refining processes.

I assumed that decomposition of the silver chloride with heat back to silver and chlorine would be something like how light will reduce silver chloride (or other silver halides like bromide or iodide) back to metal, like what is used in photography, but what works for photography would not work in refining, or would be impractical for use in the refining process as you would not be able to thoroughly convert all of the silver chloride easily, only the crystal's on the outer surface exposed to light would convert back to metal with the majority of the powders or crystals of silver chloride left unconverted not exposed enough to light to complete the process.

I do know for fact heating silver chloride to melt it, much of the silver will be lost in the white fumes.

I also have read where gold or silver with chlorides involved are volatile even at the temperatures used to roast ore, so they will also be volatile if we are incinerating gold or silver powders with chloride salts involved, or we would have some loss of silver if we attempted to incinerate a silver chloride powder.


How should we recover the Ag from AgCl?
Convert it back to silver metal.
 
The problem I'm having sounds as follows; I have completely leached MLCC powders which is like white sand that turns into mud when water is added. Together whit that sand I have lots of AgCl. So even If I tried to convert it I would still have Ag With the MLCC powders. And I don't know if something will go wrong if I did the usual AgCl conversion method. Which brings me to think that If I do convert it together with the MLCC powders Then I'll have Ag and powders, Incinerate to eliminate most of the Chlorides? and the wash thoroughly whit hot Distilled water washes to remove any residual Chlorides. And then Leach the sludge with HNO3 for Ag?

I might give it a try, Can someone give me a link to Harold's incinerating method? I really couldn't find it Via the usual search and the search engine on Steve's Website.

:mrgreen:
 
If you have silver chloride mixed with white sand, you can dissolve the silver chloride with ammonia, and then remove it from the sand, and filter the solution and precipitate the silver chloride back out of solution with HCl, (for safety sake acidify the silver diammine solution as soon as possible).

I think it takes a lot of ammonia to dissolve the silver chloride.

one thing I would look into doing is to try and separate as much of the silver chloride from the majority of the sand as I could by mechanical means.

if the sand particles are large enough a filter screen sometimes works to separate most of the larger particles from the finer powders like silver chloride (some times a little stirring and crushing with a glass rod to get the finer powder rinsed through the plastic screen.

Another thing to consider silver chloride is fluffy and will usually float around for a while when heated in a solution, while sand or heavier metals, salts or material will settle for the most part fairly fast, you can also try this to attempt to separate at least a portion of the silver chloride and sands, stirring the heated solution letting the sands settle and cypher off solution with the floating silver chloride powders ( a suction bulb tool that looks like a turkey baster tool works great for transferring liquids).

The mechanical separation will transfer some of the finer sand.

The other option is to convert the silver chloride to metal, I would use one of the replacement methods (Iron and dilute H2SO4) or (aluminum and HCl) methods, I think these would work better with the contaminates you have, than the NaOH karo method which does not seem to work well with contaminates.

once silver chloride is converted back to metal in the powders and sands, they can be washed in a solution of NaOH and then rinsed well to remove the salt water, then dried crushed and incinerated to red hot, cooled and are now ready to use the dilute nitric to remove silver and or Palladium
 
Thank you for the explenation; butcher.

It really helps when someone else has a bigger light bulb then myself; great information emerges! :mrgreen:
 
Just another thought here, if you have palladium incinerating it can form palladium oxides it may or may not convert all of the palladium metal powders to oxides.

Palladium metal or powders will dissolve in dilute nitric acid or aqua regia.

Palladium oxide will not dissolve readily in dilute nitric acid or aqua regia.

Palladium metal will not dissolve in HCl (unless strong oxidizers are added).

Palladium oxide will dissolve in HCl.

In Hokes book we learn we can take a mix of palladium oxide and palladium and put them both into solution, by heating HCl and adding it to these powders, which will put the palladium oxide into solution (but not the palladium metal powder) then without filtering, we can add HNO3 and water to form aqua regia which will also put the palladium metal into solution.


Something to consider if you do have palladium in with these white sands, incinerating is very likely to oxidize at least some or all of the palladium, so if you use nitric after the incineration to dissolve the silver, you would be able to dissolve any palladium metal powders, but not the palladium oxide into that nitric solution, in this case one option would be to test the nitric solution for palladium, if it tested positive, then it will be very likely the remaining white sands would contain palladium oxide.

There can be different methods to recover metals, sometimes we have choices and need to make a decision of what approach would be best in our situation, to help us decide a good understanding of how these metals react in different situations or solutions helps us decide how we will approach the problem, this is where our education shines, and Hokes book, her getting acquainted experiments, and understanding what she teaches helps us to decide how to approach the problem, or how not to create a problem, or how to get out of the problems we create.

Someone else may have a different or even better idea of how to recover the metals from those white sands. Keep studying Hoke's book and you can come up with a better solution or method.
 
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