Cleaning silverware

[Greg Boyles]

Interesting. here is another method for cleaning silver that you could try......from wikipedia http://www.sciencedirect.com/science/article/pii/0022508883900954

 

to air or water containing ozone or hydrogen sulfide, the latter forming a black layer of silver sulfide which can be cleaned off with dilute hydrochloric acid

 

I assume it works simply by destablising the sulfide tarnish thus allowing it to be rubbed off easily.

 

But you wouldn't want to leave the silver in it for to long as you may end up converting the black sulfide tarnish to crusty chloride deposits.

 

This patent, found via google scholar, also indicates that ammonia is capable of converting silver sulfide to diammine silver plus free sulfurous by-product. Hence ammonia is useful for cleaning the tarnish from silverware.

 

http://www.google.com.au/patents?hl=en&lr=&vid=USPAT5308381&id=qcwlAAAAEBAJ&oi=fnd&dq=dissolving+silver+sulfide+with+ammonia&printsec=abstract#v=onepage&q=dissolving%20silver%20sulfide%20with%20ammonia&f=false

[John Cuthber]

And yet the silver wire I put in some ammonia back here

http://www.scienceforums.net/topic/62131-cleaning-silver/page__st__20

is still black with sulphide. Of course, as I said before, that's exactly what you would expect from the published data on the solubility of silver sulphide and the strength of the complex that silver ions form with ammonia.

 

Do you realise that something doesn't need to be true to be patented?

Edited January 6, 2012 by John Cuthber

[Greg Boyles]

And yet the silver wire I put in some ammonia back here

http://www.sciencefo...er/page__st__20

is still black with sulphide. Of course, as I said before, that's exactly what you would expect from the published data on the solubility of silver sulphide and the strength of the complex that silver ions form with ammonia.

 

Do you realise that something doesn't need to be true to be patented?

 

There has been one person so far who has some knowledge and experience of chemstry, beyond my first year BSc, and who does not agree with you John.

 

 

We are all well aware of your opinion.

 

 

Now unless you can back up your position with a PHD and professorship in applied chemistry (I doubt it) then butt out!

Edited January 7, 2012 by Greg Boyles

[Phi for All]

Now unless you can back up your position with a PHD and professorship in applied chemistry (I doubt it) then butt out!

!

Moderator Note

This is a discussion forum, Greg Boyles, and while you may have started the thread, you don't get to decide who responds to you. If you have a problem with the content of a post, please use the Report button (as others did with your posts).

 

And if you don't want this thread to get closed like the last one, you WILL treat others civilly.

[hypervalent_iodine]

Both of you, stop with this ridiculous ad hom back and forth.

 

Greg, ammonia does not remove Ag2S, it removes Cu2S. Copper is a common impurity in silver, especially sterling silver, which is why ammonia is often quoted as being useful by people who don't really know what they're doing.

[Greg Boyles]

Both of you, stop with this ridiculous ad hom back and forth.

 

Greg, ammonia does not remove Ag2S, it removes Cu2S. Copper is a common impurity in silver, especially sterling silver, which is why ammonia is often quoted as being useful by people who don't really know what they're doing.

 

OK well I can accept that - makes sense to me. To what extent is copper an impurity in silver?

 

 

If silver iodide, chloride and sulfide have varying solubility, albeit very low, in water then logically they would also have varying solubility in ammonia solution also, and probably at least slightly higher than in pure water. Which is to say that ammonia should be capable of dissolving some Ag2S varying with temp and conc of the ammonia.

 

As to how effective and practical ammonia is at cleaning silver might be a different matter. I accept that ammonium thiosulfate (from what I have been reading) is a much stronger chelating agent than ammonia. But it is not something that you could lay your hands on around the house.

 

The electolytic process involving aluminium sounds like the easiest, most effective and practical method however.

Edited January 7, 2012 by Greg Boyles

[hypervalent_iodine]

I'm not sure on the percentage. It varies with the alloy, obviously. It wouldn't be terribly much in comparison to the silver, however.

 

Using ammonia is far less of an effective approach than using thiourea salts, etc., since it's not going to get rid of all the blemishes, only the copper impurities. Depending on how homogenous the distribution of copper is, you will likely get patchy removal. Why waste your time not doing the job properly/at all when bicarb and aluminium foil is a cheaper and easier option that actually works?

 

I'm not sure what your point is with the ammonium thiosulfate. It's fat from being the same as ammonia solution, so it's hardly a comparison. I don't even think it would work that well, since ammonium thiosulfate is used for leaching silver and gold, not cleaning it. I mean, if your objective is to destroy the object then I guess it's what you want. Did you mean the thiourea salt?

 

Edit: You may be interested in this paper.

[Greg Boyles]

I'm not sure on the percentage. It varies with the alloy, obviously. It wouldn't be terribly much in comparison to the silver, however.

 

Using ammonia is far less of an effective approach than using thiourea salts, etc., since it's not going to get rid of all the blemishes, only the copper impurities. Depending on how homogenous the distribution of copper is, you will likely get patchy removal. Why waste your time not doing the job properly/at all when bicarb and aluminium foil is a cheaper and easier option that actually works?

 

I'm not sure what your point is with the ammonium thiosulfate. It's fat from being the same as ammonia solution, so it's hardly a comparison. I don't even think it would work that well, since ammonium thiosulfate is used for leaching silver and gold, not cleaning it. I mean, if your objective is to destroy the object then I guess it's what you want. Did you mean the thiourea salt?

 

Edit: You may be interested in this paper.

 

No, thiosulfate. Because I was reading about its use in removing unreacted AgCl (or what ever it is) in photographic emulsions and it also mentioned that it has also been used to leach the silver out of silver ores. Look it up on Wikipedia for yourself.

 

And since one of the silver ores is Ag2S (aragonite I think it was) then, since there is no specific mention of it not working for aragonite, then logically there is no reason why it should not also work in cleaning the tarnish off silver. Apparently it is often used as an alternative to cyanate, which is highly dangerous due to possible release of cyanide gas, in gold and silver mining.

 

There is also a number of mentions of ammonia being used for the same purpose of leaching out the silver from silver ores.

 

In fact look here:

 

http://www.electronicsrecyclingdirectory.com/article/ammonia-extraction-of-gold-and-silver-from-ores-and-other-materials.html

There have been numerous attempts made to overcome such problems associated with refractory ore processing using various chemical reagents such as thiourea.sup.1,2, halogen chemicals.sup.3 and ammoniacal thiosulfate.sup.4. However, though these chemicals are effective in dissolving precious metals in solutions, due to high reagent consumption and/or poor selectivity, these reagents are not being adopted by the precious metal industry.

 

Leaving aside the issue of them not being cost effective, ammonium thiosulfate is apparently quite effective and I have also read that ammonium thiosulfate gives off ammonia. Why specifically ammonium thiosulfate and not sodium thiosulfate. Perhaps the combination of two chelating agents is more effective than the individual ones.

 

 

But yes I acknowledge that such cleaning methods remove silver metal and slowly erode the silverware.

No different to polishing them with Silvo however.

[hypervalent_iodine]

IIRC, sodium thiosulphite does the same thing. It's not the ammonium ion that's doing the work, it's the thiosulphate, which binds particularly well to silver.

Edited January 7, 2012 by hypervalent_iodine

[John Cuthber]

Greg,

Re "Now unless you can back up your position with a PHD and professorship in applied chemistry (I doubt it) then butt out!"

please let me know what letters I need to put after my name that will make the silver sulphide decide to ignore the solubility data and dissolve in the ammonia?

also, do you realise that the outcome of an experiment is a fact, not an opinion, so your saying "We are all well aware of your opinion." doesn't make sense.

Anyway, to answer one of your questions, there's typically about 7.5% copper in silver used in jewellery etc.

http://en.wikipedia.org/wiki/Sterling_silver

 

re "If silver iodide, chloride and sulfide have varying solubility, albeit very low, in water then logically they would also have varying solubility in ammonia solution also, and probably at least slightly higher than in pure water. Which is to say that ammonia should be capable of dissolving some Ag2S varying with temp and conc of the ammonia."

In the thread I cited earlier, I gave you the data to let you calculate that solubility at room temp and a reason why the dependence on temperature might not be what you expect.

Have you calculated the solubility of silver sulphide in ammonia solution?

If not, may I suggest that you do so before you speculate further?

[Greg Boyles]

Greg,

Re "Now unless you can back up your position with a PHD and professorship in applied chemistry (I doubt it) then butt out!"

please let me know what letters I need to put after my name that will make the silver sulphide decide to ignore the solubility data and dissolve in the ammonia?

also, do you realise that the outcome of an experiment is a fact, not an opinion, so your saying "We are all well aware of your opinion." doesn't make sense.

Anyway, to answer one of your questions, there's typically about 7.5% copper in silver used in jewellery etc.

http://en.wikipedia....Sterling_silver

 

re "If silver iodide, chloride and sulfide have varying solubility, albeit very low, in water then logically they would also have varying solubility in ammonia solution also, and probably at least slightly higher than in pure water. Which is to say that ammonia should be capable of dissolving some Ag2S varying with temp and conc of the ammonia."

In the thread I cited earlier, I gave you the data to let you calculate that solubility at room temp and a reason why the dependence on temperature might not be what you expect.

Have you calculated the solubility of silver sulphide in ammonia solution?

If not, may I suggest that you do so before you speculate further?

 

The point is that equilibrium constants are effected by temperature and pressure. So it is entirely possible that ammonia in high concentration, temperature and pressue could be enough to remove small amounts of tarnish.

 

You insisted on nit picking about differences between below 0 solubility of various silver salts, so I will insist on nit picking about the differences in solubility in ammonia solution that higher temperature, pressure and concentration can and would make.

[John Cuthber]

You seem to have misunderstood something I pointed out in a previous thread.

 

Raising the temperature may well cause the complex formed by ammonia and silver to break up.

Once the silver is "free" from the ammonia, it is more likely to react with sulphide ions and precipitate.

It is entirely reasonable to suspect that the solubility of silver sulphide in ammonia solution will fall as the temperature rises.

 

Do you actually have any data about this, or are you just assuming, in the face of the theoretical prediction, that you will be right?

 

The effect of the concentration of the ammonia is already accounted for in the calculation which you haven't done. Please do so, I'm sure you will find it very informative.

 

The effect of pressure will be very small because the change in volume is very small.

[Greg Boyles]

You seem to have misunderstood something I pointed out in a previous thread.

 

Raising the temperature may well cause the complex formed by ammonia and silver to break up.

Once the silver is "free" from the ammonia, it is more likely to react with sulphide ions and precipitate.

It is entirely reasonable to suspect that the solubility of silver sulphide in ammonia solution will fall as the temperature rises.

 

Do you actually have any data about this, or are you just assuming, in the face of the theoretical prediction, that you will be right?

 

The effect of the concentration of the ammonia is already accounted for in the calculation which you haven't done. Please do so, I'm sure you will find it very informative.

 

The effect of pressure will be very small because the change in volume is very small.

 

I have no doubt that if you heated diammine salts you would cause the ammonia to out gas and the complex ion to break apart.

 

But to heat ammonia solution without losing its strength you would need to do so in a sealed vessel. In which case the diammine salts would undoubtedly remain stable.

 

And we are talking about raising the temp to perhaps 80 degrees celsius of so, not to hundreds of degrees.

[John Cuthber]

This bit " the diammine salts would undoubtedly remain stable." is just plain wrong.

Even if you keep the lid on the sample the complex will still dissociate- the ammonia won't leave the solution- it just leaves the complex.

 

Incidentally, at 80C most of the ammonia would boil off unless you were using an autoclave. This has no place in a sensible discussion about cleaning silverware.

There are no practical conditions where you can wash the tarnish off silver with aqueous ammonia.

 

The ozone is an interesting idea but most people don't have an ozone generator.

[Greg Boyles]

This bit " the diammine salts would undoubtedly remain stable." is just plain wrong.

Even if you keep the lid on the sample the complex will still dissociate- the ammonia won't leave the solution- it just leaves the complex.

 

Incidentally, at 80C most of the ammonia would boil off unless you were using an autoclave. This has no place in a sensible discussion about cleaning silverware.

There are no practical conditions where you can wash the tarnish off silver with aqueous ammonia.

 

The ozone is an interesting idea but most people don't have an ozone generator.

 

John it would be an easy matter to put your silverware in a tub with a sealable lid, add your .88 ammonia, close the lid (with some duct tape if necessary) and immerse the tub in a laundry trough full of hot water.

 

So don't give this nonsense about it having no place in sensible discussion - it is entirely possible.

 

 

And I some one has made an valid point about the nature of silver tarnish via PM.

 

How can you be so sure that all silver tarnish is entirely silver sulfide? Perhaps if you lived in Bejing or near a mangrove swamp!

I believe that Ag2O is also black or dark brown!

[hypervalent_iodine]

I have to ask why you are holding onto this idea so fervently? The majority of tarnish-type blemishes on silver are in the form of silver sulfide. Ammonia will not remove silver sulfide. It is really that simple.

 

Are there any other methods you would like to discuss?

[John Cuthber]

Hypervalent_iodine, perhaps the text of the email I just got from Greg will clarify that: it says

"John Cuthber,

 

Greg Boyles has sent you a new personal conversation entitled "Hello John".

 

Greg Boyles said:

======================================================================

In the immortal words of Robyn Williams in Good Morning Vietnam.

 

"You are in need of a **** *** more than any man in history"

Anyway Greg, re "How can you be so sure that all silver tarnish is entirely silver sulfide?"

I'm not. I never said it was. So you are straw-manning . Please don't.

As has already been discussed it's quite likely that some of it is copper sulphide .

However, at least some of it is Ag2S (as witnessed by the smell of H2S when you remove it with Al and soda).

Unless you remove that you won't clean the silver.

 

Silver oxide is, indeed, black

Silver oxide is soluble in ammonia. The tarnish on the silver I tested did not dissolve in ammonia.

Therefore it is not silver oxide.

You were aware of those facts. You chose not to think things through before posting.

 

 

As for the tub of hot ammonia, I remind you that this is a science forum.

Unless you do the experiment you are just guessing (and your guess is at odds with the known facts and reasonable theories).

 

And I'd still like to see your calculation for the solubility of silver sulphide in ammonia solution.

 

Edited to censor Greg's naughty words.

Edited January 7, 2012 by John Cuthber

[Phi for All]

!

Moderator Note

Thread closure imminent. Porn rules violation, put them back in your pants, gentlemen.

[Chemistoftheelements]

In the previous thread, I posted some of my conclusions from an experiment I conducted on the removal of the tarnish formed on 99.99% fine silver, and on the alloy sterling silver. My intention at the time, was to add a little to the discussion based on my experience, not to further an argument.

 

For the sake of science, I will add the results of a second experiment, using the same piece of 99.99%, i.e. fine, silver (as I don’t have a great deal of this available to me), and some more tarnished sterling silver, after treatment with 9% ammonia solution:

 

1) In the second experiment on the fine silver, there was no further removal of tarnish, and the original, unpublished observation of H2S evolution (which came as a surprise, as there’s no obvious mechanism for this to occur) was not replicated in the second experiment.

 

2) The sterling silver again, in the second experiment, markedly de-tarnished, to the extent that this could be used as an effective method of at least helping to completely remove the tarnish from sterling silver, at least of it’s more usual composition, in which copper is the alloying element. No H2S evolution took place.

 

The only firm conclusions I reach from the above experiments are as follows:

 

1) The tarnish layer formed on fine silver is of a different chemical nature of that formed on

 

sterling silver. The species in question were not identified by the author of these experiments.

 

2) More study is warranted into the differences in the observations between the first and

 

second experiments on fine silver, and into the nature of the tarnish films formed on fine, and sterling, silver.

 

 

 

Onto the topic of humility and politelness now, and may I add that after my original post on the topic, which was intended for the purpose of encouraging scientific discussion, I gained the distinct impression that John Cuthber had formed some sort of grudge, as evidenced by his unwarranted behaviour in the Neodymium chloride thread in the Inorganic chemistry section.

 

Although I don’t necessarily condone the methods which Greg used in this thread, it is clear that he was provoked by the same behaviour in the previous, now closed, thread on silver tarnishing, as I was in the Neodymium chloride thread. I can’t say I blame him, as I also have a low tolerance for arrogance and lack of humility. It has been demonstrated by further discussions in this thread (after the conversation between Greg and John Cuthber, that Greg is ammenble to civilised discussion with others who use a more civil approach; it is largely dependent on the manner in which any correcting and commenting is done, and this applies to most people. Please refer to my point about politeness on page 2 of the Neodymium chloride thread in Inorganic chemistry). I joined this forum for the sake of discussing chemistry, and I really am not interested in arguing with people who cannot grasp the basic rules of social interaction. Regretfully for me at least, I’m out of here.

 

 

[John Cuthber]

The truth is I get pissed off with people who make false statements based on a half understood theory, I usually start off rebutting them quite politely.

For example in the thread referred to the OP asked about the mechanism and details of the technique for removing tarnish from silver using aluminium foil and soda.

Greg's reply was " For example, silver chloride and silver sulphide salts are both insoluble in water, but if you add enough ammonia (as in cloudy ammonia) these insoluble salts will dissolve to form Ag2(NH3)4S and Ag(NH3)2Cl. "

Now, let's be clear about that: it was scientifically wrong. The sulphide does not (as at least two experiments here have shown).

It was also nothing to do with the original question.

 

I really don't think my reply was "provocative". I said

"I'm a long way from sure that the ammonia complex is strong enough to dissolve silver sulphide.

It won't dissolve silver iodide and I think the sulphide is even less soluble than that.

Anyway, it doesn't actually answer the original question."

 

Greg's next comment was, once again, simply incorrect: he said "As far as the formation of complex ions goes, it is irrelevant how soluble the simple salt is to begin with, whether it is silver sulphide or silver chloride."

As has now been proved, it jolly well does make a difference.

He then added "With ammonia, the silver ammino sulphide that is formed is completely soluble in water "

Again, he is repeating something that is flat out wrong.

 

A few posts later I listed all the false statements he made.

 

 

Now this is a science website.

Posting stuff that isn't right, repeatedly and after you have been told it's wrong is not an acceptable way to behave.

How long should we put up with someone saying things that simply are not true before we stop being polite about pointing this out?

 

 

The funny thing is that much the same happened with the thread on Nd compounds.

Chemistryoftheelements assertion that "Oxidise this resulting solution to produce Pr2 O(SO4)3(?), a higher basic sulfate of praseodymium which will be insoluble." simply isn't true.

He never put forward any sensible evidence for it and he ignored the fact that it goes against the established data.

Now, if he were proposing to waste his own time on this that would be his problem, but he was expecting to send another forum member on what could only ever be a wild goose chase.

I guess people will make up their own minds about it. In particular I guess Greg will realise that sending insulting personal messages is unhelpful.

Edited January 8, 2012 by John Cuthber

[mississippichem]

I agree with John Cuthber. An easy Ksp look up and two empirical observations are hard to argue with.

 

And the solubility of the tarnish salt or complex most certainly matters. In fact, it's about all that matters.

 

This is really a chemistry 101 question.

Edited January 8, 2012 by mississippichem

[Greg Boyles]

If you put tarnished silver in liquid ammonia then the solubility of Ag2S in water is totally irrelevant to whether or not the ammonia is capable of breaking the bonds in Ag2S. Assuming complex ions can form in non-aqueous solutions.......either way it should get across the point I am/was trying to make.

 

However I will concede that the solubility of Ag2S in water is probably not totally irrelevant for aqueous ammonia and that this statement of mine was an over statement.

 

Some interesting facts I have learned along the way.......

 

Silver can be tarnished through contact with organic sulfur containing compounds such as latex and perhaps sweat from hands, I guess these break down to release tiny amounts of H2S and over a long period......

 

Have also noticed a number of sources stating that pure silver is less prone to tarnishing than stirling silver, I guess because the copper is more reactive than the silver. That would mean that ammonia is more effective on stirling silver than it is on pure silver.

 

And chemistoftheelements, would you be in a position to repeat your experiments with stirling silver and pure silver and with warmed 0.88M ammonia in a sealed container?

 

I am interested to know if it would really make any noticeable difference to dissolving Ag2S tarnish. I don't have any silverware or silver wire on hand although I could make myself a small amount of 0.88M ammonia. Used to make it in my younger days for the purpose of making touch powder and I still have the flasks and stoppers etc.

Edited January 9, 2012 by Greg Boyles

[John Cuthber]

"If you put tarnished silver in liquid ammonia then the solubility of Ag2S in water is totally irrelevant to whether or not the ammonia is capable of breaking the bonds in Ag2S."

Except that, if ammonia broke those bonds, then it should still do so in the presence of water.

 

"I am interested to know if it would really make any noticeable difference to dissolving Ag2S tarnish. I don't have any silverware or silver wire on hand although I could make myself a small amount of 0.88M ammonia. Used to make it in my younger days for the purpose of making touch powder and I still have the flasks and stoppers etc. "

I bet you don't mean that.

The ammonia solution I used ( and found not to work, even on heating) was more than 0.88M.

[Greg Boyles]

"If you put tarnished silver in liquid ammonia then the solubility of Ag2S in water is totally irrelevant to whether or not the ammonia is capable of breaking the bonds in Ag2S."

Except that, if ammonia broke those bonds, then it should still do so in the presence of water.

Regardless the ability of ammonia to break those bonds, or not, is not determined by the solubility of Ag2S in water.

[hypervalent_iodine]

Greg, ammonia doesn't react to form a complex with silver sulphide (as I think John pointed out quite some posts ago), so your argument is still moot. It doesn't matter how many posts you spend arguing semantics, the fact remains that ammonia does not and will not remove silver sulphide from silverware.