Extracting silver from silver nitrate solution for school project

A. Recover it from what or where? Sorry, I have no idea at all of what you have in mind.
Please set the scene so people can advise what might be involved.

Luck & Regards,

Hi,

A. Firstly, don't leave it so late next time! Secondly, you need to reduce the silver ions to silver metal. This is done with a less noble metal being put into the solution and letting it dissolve. The dissolution process will result in the silver being precipitated out. (Now tell us which less noble metals will do this and how). Alternatively, you can use a reducing agent such as glucose or formaldehyde (very nasty and pongy) and this will throw out silver onto the sides of the vessel.

A. Have a look at letter number 25979, "Recovering silver via electroplating"; that should help you out.

You may want to just read the letter and not actually try to do it as some of the materials needed are not very nice to use.

A. The easiest way to extract silver - quantitatively - from silver nitrate solution, is simply adding sodium chloride (table salt) solution. Silver chloride will precipitate and is quite easily decanted and/or filtered. This is probably what they wanted in the first place for you to do. To reduce silver chloride into metallic form is much more complicated. You might wash and wash and wash again the precipitate, then make the reduction with sodium hydroxide and formaldehyde. I do not recommend this to anyone because of the toxicity of formaldehyde.

One easy way is to mix the washed silver chloride into photographic fixer and then electrolyze using graphite anode and stainless steel cathode, to produce silver of 94 to 99% purity.

A. Adding plain copper will work.

A. Take the Silver Nitrate solution and add common table salt. The silver will turn to a cottage cheese looking flocculent and drop to the bottom. Filter off the Fluid and neutralize with sodium hydroxide. Then add Sodium Hydroxide slowly and carefully to the flocculent stirring as you go. It will turn the Silver Chloride to silver oxide. Let it dry and then grind it down to powder. Then mix with borax [affil links] and smelt in a crucible in a furnace at 1200-1400 °F for 2 hours. Cover the entire mixture with 1/2 inch of Borax on top of the silver oxide/borax mixture.
Once you have complete melt pour into an ingot mold.
Your result will be a very high purity Silver bar.

A. Cheapest and safest way to claim high purity silver
Hang a piece of pure (99.9% to 99.98%) copper bar. For faster results try copper as anode and pure silver rod cathode.
Please follow the above method for safety and it's cheap, good.

A. Robert, you haven't given us much context upon which to expand from the previous excellent responses -- and we really need to know whether this is a student project, industrial need, or hobbyist undertaking.

Where did you get this mix and how do you know what is in it? You have only one chance?! Maybe you're a high schooler and this is an experiment/exam? It should be possible to remove the iron from a mixture with a magnet; and I don't think sulfur [affil links] is soluble, so you can probably filter it. Best of luck!

If this is not for an academic requirement, but an actual industrial need, I must completely disagree with your characterization about having only one chance! A chemist never attempts to react an entire industrial quantity batch based on book knowledge, but only after he has first proven his chemistry with small scale samples does he scale the quantities up. (You might include that note for extra credit if you are a student).

If you are a hobbyist, we must warn against the danger of creating explosive silver fulminates (that can explode from simple vibration) if you are fooling with silver chemistry that you are unfamiliar with. Good luck!

A. C'mon now, Carla. Get to the library and study the chemistry of silver nitrate; then propose an idea or question and we'll be happy to help you with its strengths and weaknesses. You're supposed to give this serious thought, not ask someone for the answer. Good luck!

Regards,

A. Hey that is really cool! I have to do that too! What I am going to do is get five different metal strips and put them into the solution to see which one attracts the most silver. You may not have the access to the metals and they take some time to be shipped. you only have 4 days so I don't recommend waiting! That is my only way to do this. Sorry! Maybe it can be of some help to you! My dad is a chemist so that is what he told me to do! Good luck with this! I do hope that you succeed.

Solvent Extraction

A. Hi Sohil. Yes, it seems to me that if you simply raised the pH you'll precipitate all of those heavy metals together, not making progress. I know less about this than you do, but I do see good discussions above about either precipitating the silver with table salt, or plating it out by displacement onto solid copper.

Please try to frame your question in terms of what has already been offered because it's the kiss of death to potential responses if the helpers feel that someone is asking them to repeat their efforts rather than taking the time to read what they already wrote :-)

Regards,

A. Hi Gostime. There should be some context; it seems unlikely that you have no textbook, workbook, instructions from the teacher, hypothesis, warnings, just "Do it!".

But you can take two 2-foot long lengths of copper wire, and coil most of their lengths around separate pencils, then remove the pencils. Attach the uncoiled ends to each pole of a 1-1/2 bolt "D" cell battery and don't let the wires touch. Put the coiled ends into a beaker (again, don't let them touch). Put your silver trioxonitrate solution into the beaker. One of the two wires will turn silvery. As soon as you see some silver on it you have electrolytically extracted silver using silver trioxonitrate solution, and have completed the assignment. Good luck.

Regards,

A. Hi Gostine

After a (very) long career as a professional chemist, I have never heard of trioxonitrate (v)

You will find that you will find the answer more easily if you refer to silver nitrate.

Trioxonitrate is not recognised by the International Union of Pure And Applied Chemistry IUPAC who are responsible for naming chemicals. Using a non-standard name for common chemicals has serious safety implications.

A. Hi Luke.
1. Sandpaper or scotchbrite should easily remove any coating on your copper rod. Then rinse off the dust with water, and immerse it.
2. You won't be able to remove the trace metals once you've placed the copper rod in it because for each two atoms of silver deposited on the copper rod, one atom of copper dissolves into solution ... and sodium chloride will not precipitate the copper; rather, it will stay in solution.

Oops, I replied to your 2nd letter before I noticed the first :-(
-- so let's see what others have to say.

Regards,

A. Hi Luke

Ammonia can react with silver salts to give a range of highly sensitive explosive compounds.

In a Haz Chem facility you should know this

The simple answer to your question is to simply stir in some (clean degreased) steel wire wool and stir.

A. Whether you use copper to cement the silver or use a chloride to precipitate silver chloride, about the only source of contamination will be the solution mixed in with the solids. The solids themselves are of high purity. The more you rinse these solids, the higher the purity of the silver. Hot water rinses are best.

I would absolutely avoid the use of copper wire for cementation. The cemented silver intermingles with the wire and makes separation difficult. Also, the small wire tends to dissolve and release slivers of copper that contaminate the silver. The best copper to use is bare scrap copper buss bar (say, 1/4" X 2" or 3") that contains no solder and is not plated with tin or silver. Put the silver solution in a plastic 5 gallon bucket and use 5 or 6 lengths of buss bar. The pieces of buss bar should be long enough to stick up out of the solution so you could easily remove them

I would advise against steel wool. It's easy to do but recovery of the silver is more difficult.

All in all, if you want fine silver (at least 999.0 fine) you will have to put the recovered silver through an electrolytic silver cell. Chemically processed silver, no matter what process you use, will not normally meet the accepted 999.0 fineness requirement. There is an oxalic acid process that may reach this purity, but it is tricky.

A. Please use hydrazine hydrate to reduce silver from silver nitrate solution.

A. Hi Shiina. You have written the reaction almost correctly, it is actually:
Cu + 2 AgNO3 ---> 2 Ag + Cu(NO3)2

I'll write it in slightly fuller form here, to include notations about the oxidation states of the atoms and ions:
Cu⁺⁰ + 2 Ag⁺¹NO3^-1 ---> 2 Ag⁺⁰ + Cu⁺²(NO3^-1)2

Cu⁺⁰ means the copper is in metallic form as an atom, whereas Cu⁺² means it is in ionic form, missing two electrons. Similarly ...

Ag⁺⁰ means the silver is in metallic form as an atom, whereas Ag⁺¹ means it is in ionic form, missing an electron.

Actually, there is nothing "in" copper or silver except copper and silver -- they are irreducible elements. But silver has a stronger affinity for electrons than copper (it is more "noble"), so it is capable of "stealing" electrons from copper. So what happens in your reaction is you put copper atoms into a solution of silver ions, and the silver ions steal electrons from the copper atoms, thereby becoming silver atoms, while the copper atoms become copper ions.

Regards,

A. Hi Eric. Chemical reactions of this sort move in one direction, towards lower energy states -- that's what powers them. We'll see if anyone can offer encouragement about a practical way of putting the necessary energy back in, via heating or whatever, but I doubt it.

Regards,

A. Don't see what's wrong with steel wool.

Let the Ag plate out, dissolve away the Fe with HCl, then melt it down.

A. Eric, why do you want to reuse the HNO3? Is it because you are trying to save money on nitric? If you can find a decent method to eliminate the copper, the cost will most likely exceed that of just using fresh nitric for the next batch. Although I've been a professional refiner for 50 years, I've never known of a good simple inexpensive method to do what you want to do.

I'm not a fan of using steel wool to drop the silver from a nitrate solution. For one thing, it's almost impossible to leach out the excess Fe with HCl without converting at least some of the silver to silver chloride. After melting the silver, the AgCl will form in a layer between the slag and the Ag and will most probably be lost. Also, AgCl can evaporate at the Ag melting temperature. sodium carbonate / washing soda [affil links] can convert AgCl to Ag in the melt but, to do so, the particles of AgCl must intimately be in contact with the particles of Na2CO3. Also, this reaction will quickly erode the crucible. The use of steel wool is not necessarily hassle-free.

I've always used copper to cement out the silver. It's very simple, efficient, and hassle-free. One gram of copper will cement out 3.4g of silver. However, if you use an excess of HNO3 to dissolve the Ag, this excess will dissolve copper also and copper will be wasted. Always try to use only enough HNO3 to dissolve the silver, with no extra. With an open top container, it takes about 1.2 ml to dissolve 1g of silver. If the container is covered, it can take a little less HNO3.

For a more thorough discussion of this process and most every other refining process known to man, go to goldrefiningforum.com. I am a moderator there under the name goldsilverpro.

Good luck

Silver Nitrate

A. Hi Cheri. It probably doesn't matter a real lot how much distilled water she uses, but for extra credit she should look up the solubility of silver nitrate, and use that to justify how much DI water to add. For example, if she finds that the solubility in room temperature water is 2 grams per ml, she can say that she needs at least 25 ml of water to dissolve the 50 grams of it.

If the teacher wants her to show the reaction
AgNO3 + NaCl => AgCl (precipitates) + NaNO3,
where one molecular weight of NaCl precipitates one molecular weight of AgNO3, she can also say that there obviously can be no more than 50 grams of Silver Nitrate left after using it on the copper, and she can calculate how much table salt she needs to add to precipitate it: 50 grams x (molecular weight of NaCl molecule) / (molecular weight of AgNO3 molecule). Good luck.

Regards,

A. Hi again. From the fact that she has silver nitrate (AgNO3), copper (Cu), & DI water, and is supposed to supply table salt (sodium chloride / NaCl) -- and with no other input -- you're asking people to guess what the experiment is about, how it ought to be conducted, what the results are expected to be, and -- most importantly -- what she's supposed to learn from it :-)

If she has no idea what she's doing, and received neither instructions in what to do nor a goal from the teacher, this seems to be a make-work project. Darwin himself said that to go into a gravel pit and sort the stones by size or color with no bigger objective is to waste your life.

As a guess, I think she is supposed to mix the silver nitrate into DI water, immerse the copper into the solution and observe silver plating out onto the copper; and after the plating is done, she's probably supposed to add table salt to the solution to precipitate the silver so it can be filtered out from the solution back in school.

But she has to attempt to learn something, or this is all simply a ridiculous waste of your time & mine. I already suggested some things that can be learned ...

First, she should look into the issue of 'solubility'. If you add several spoonfuls of sugar to your coffee, some of it (maybe one teaspoon?) will dissolve and stay dissolved (the coffee will become and stay sweet), and the rest of the sugar will slowly settle into a sludge at the bottom of the cup when you stop stirring. How much stays dissolved often depends on the temperature of the water. Similarly, some amount of silver nitrate (AgNO3) will dissolve into water and stay dissolved, so I linked to a Wiki article for you that told you the solubility of silver nitrate at different temperatures. Did she see the line that says the solubility is 256 g/ 100 ml at 25°C there? It's grade school math, not high school math, that if 256 g will dissolve in 100 ml, then 50 g will dissolve in 19.53 ml of DI water. So she will need a minimum of 19.53 ml of DI water, which she should explain for credit, and as a practical matter she can use say 25 ml of water to dissolve her 50 grams of silver nitrate and explain why.

The second thing she certainly is supposed to learn is that while silver nitrate (AgNO3) is very soluble in water, silver chloride (AgCl) is certainly not -- that is, silver chloride does not dissolve in water. She can find silver chloride on Wiki and see that its solubility is lower by a factor of about a million! She is probably supposed to add table salt to the silver nitrate and understand that the reaction will be:
AgNO3 + NaCl => AgCl (precipitates) + NaNO3
as I previously said. If she adds one molecule of table salt (sodium chloride, NaCl) for every molecule of silver nitrate (AgNO3), she will get one molecule of silver chloride (AgCl) which will precipitate, settle out, and be filterable in school (with a simple filter not much different than a Mr. Coffee filter) and one molecule of very soluble NaNO3 which will not precipitate.

The third thing she can learn and is probably supposed to learn is how much table salt (NaCl) will be required. She has at most 50 grams of AgNO3 if that's what she started with, and some of it deposited onto the copper. If she divides this by the molecular weight of AgNO3, she'll know how many gram molecular weights of AgNO3 this means. If she multiplies that answer by the gram molecular weight of table salt (NaCl), she'll know the maximum grams of table salt she could require to precipitate out all the silver so it is filterable. She determines the gram molecular weight of silver nitrate (AgNO3) by adding the atomic weight of silver, nitrogen, and 3X the atomic weight of oxygen. She finds these in the "Periodic Table". She determines the gram molecular weight of table salt (sodium chloride, NaCl) by adding the atomic weights of sodium and chlorine. Good luck.

If this is too much to absorb in one sitting, sorry, but it's not my fault or yours, it's either the teacher's or your daughter's :-)

Regards,

A. While probably not what your teacher is looking for, a silver nitrate solution can be heated (fume hood) until the water boils off, continue heating till around 440 °C, by then the AgNO3 will decompose into Ag, O2 and NO (highly toxic!).

But I think they are looking for a chemical method.