Using acetone on copper coins - the scientific result is out

Just curious - What does sugar have to do with this discussion?

 

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Sugar has an esther group on it which, actually, is what makes it sugar. The simplist of the ketone or esther groups is cleaved off many important chemical reactions and releases acetone, and also the reverse. The ketone group is so active in Glucose that it reacts with the far half of the molecule to form a perfect sterotyped ring.

It is very unusual to hear that a ketone group is 'inert'. They are very chemically active giving most fragences their smell, sugars their usefulness in engergy production, drugs their activity and form a large group of biochemical metabolic pathyways. In fact, the esther bond, its hydolysis and estherfication probably form the most important chemical bond in science. Its the foundation for nearly every long chained molecure used in plastics to a a vast majority of nutritional and medicinal substances.

Ruben

 

When I was a medic we used acetone in medical stuff a lot to clean off tape from the skin

 

Extreamly misunderstood. Note that Verdigris is in reality Cu(CH3COO)2-H OH. Normally not found on Copper coins though. What is so commonly thought to be Verdigris is just a normal Oxydation process that Copper goes through. It starts by exposing bare Copper to Oxygen forming Cu2O. Moisture (H OH) normally shown as H2O along with Carbon Dioxide in the air then attacks the Cu2O to form Copper Carbonate [CuCO3-Cu(OH)2] and this is the greenish patina on copper that is so commonly thought to be Verdigris. To continue this reaction if your in an area such as upper Indiana where there is a large amount of Sulfites and/or Sulfates in the air, this now attacks the Copper Carbonate to form darker Greenish crytaline formations (CuSO3 or CuSO4) on Copper coins. Many people note this to happen to Copper based piping in thier homes also. Normally a swab of Vinegar on a peice of cloth will remove this from your pipes but is not nice for coins due to the 4% Acetic Acid in the Vinegar. Sorry for the chem stuff. Also, sorry about not being able to utilize the lower case numbering for the formulae.
Now after several days of the Copper Cents in the Acetone I just removed them, placed them on my patio table to dry. No rinse at all. Can't even remember how many days they were in there. Here is the results.
A 1944S in AU50 shows no change at all. Still looks like it did several days ago.
A 1972D in VG8 or better had a greenish crud when started and it is still there.
A 1974S and 1974D both MS60 or better except had some black spots when first put into the Acetone and they are still there otherwise also, no change.
My summation is if truely high grade, pure Acetone is used not much happens to a Copper coin. However, anything is possible if left in there for a few hundred years. Don't think I'll try that though.

 

This is not a question of chemistry - it's a question of logic.

1. It doesn't matter what sugars have ketones associated with them, or what the properties of those sugars are. They aren't in play here, so they are irrelevant.
2. Esters are a different class of organic compound. They aren't in play here, so they are irrelevant.
3. We aren't dealing with a ketone GROUP, which I gather in this context is talking about a ketone hanging off some other aliphatic hydrocarbon. They aren't in play here, so they are irrelevant.
4. The only thing which counts is ACETONE and acetone ALONE. It doesn't matter what any other ketones do in any other setting. All that matters is what THIS ketone does in THIS setting - that is, brief contact with metal surfaces followed by a proper rinse with very pure water.
5. The point remains that acetone is relatively inert. It has relatively few reactions :
   1. acid / base catalyzed Hydrolysis : Yes, it can cleave to form acetaldehyde and methanol. But who cares ? Are we introducing acids ? No. Bases ? No.
   2. It can be oxidized (burned) : Are we gonna light it up while on the surface of the coin ? I bet we'll get some toning then.
   3. The big one - acetone is not an oxidizing agent. It does not oxidize the metal surface.

Pure acetone is relatively inert - "Relative" meaning compared to other compounds - and only relevant in this numismatic setting.

But the real irony is this : all the chemistry - or "chem-mystery", as some call it - is irrelevant.

What really counts is the empirical experience of folks who have tried it with coins.

And it's clear it's a terrible idea using cheap-o acetone, and maybe bad all the time. I dunno.

So some real questions are :

1. Has anyone had a GOOD experience, in which the coin never discolored after a long period ? If so, do tell details.
2. When should acetone be used - and when should it be avoided ?
3. Is this considered cleaning ? Does it alter the surfaces ? If so, it is categorically out.
4. Why do dogs have black lips ? (Just seeing if you're still reading...)

Well, that's the news from Lake Wobegon - where all the men are strong, the women are good-looking, and the coins are above average !

 

1. 
   
   
   Esthers are just a subgroup of aldehydes and both are active. I spent a good part of my PhD studying them.
   
   Aldehydes, ketones, organic acids and esther bounds and all derived from each other and can be thought of as related through derivites of the carbonyl grouping.
   
   They certainly have basic and acidic as well as oxidative properies unless your not a believe in vinegar. The (=0) is an inherent Lewis acid. The related Acetonitriles have made a bit of news lately.
   
   This has little to do with Coins, but dipping silver in acetone clearly has a chemical affect. Mind you I was not trained as Chemical Engineer, just a Physical Chemist in Drug and Medical research, or Pharmacuetics. We don't run the same reactions over and over but had to devise new models for the technology of identifying new chemical entities, discovering such entities in the first place, purifying them and delivering them safely to human and animal populations, laying down the ground work for the Chemical Engineers. Therefor my perspective might be a little skewed. I see everything as reactive, especially something that is the building block for the vast majority of reactions and materials which are studied and used today. Is Acetone "relitively" inert. I'm not certain of that at all. It took years to determin that Nylon was safe.
   
   Ruben

 

Has anyone seen an online store that sells pure acetone without the extra chemicals that most of the products have at the hardware stores? I think the evaporation test is a good one to use before trying this on an expensive coin.

 

True it would be a good idea to try the evaporation test prior to use on a coin.
Not sure of on line anything being pure. I only know that in my area there are companies or organizations where you can buy just about anything. And many are not supposed to be sold either. You may want to check on line for chemical supply houses in your area. Of course if you are in a school or know someone in a school that has a well equiped chem lab they could or should be able to get you some. From my experiments I would only consider Acetone in a glass container. So far my test of Walmart Acetone in the paint department is in a can and unless you know someone in the canning buisness that can tell you the construction of those cans I would avoid that except for painting projects.
As to the questions from 900fine. Note you obviously did not read my results of leaving Copper coins in Acetone for many, many days. Being a chemist I did make one drastic error that no true chemist should make. I did not document the exact amount of time of submersion, temperatures, available lighting at all times. However, the intent was just to see what true results there are in long term submersion of Copper coins in PURE Acetone.
As to other questions. No Acetone should be avoided for cleaning coins due to to many unknown results of the purity of the substance. And basically from what I've seen it would be very difficult to detect cleaning in Acetone at least on Copper coins. Next I'll try Silver and Nickel coins.
Do all dogs have black lips? I'll start checking that also.

 

As a numismatist on a numismatist website, the only relevant issue is what acetone does to coins.

 

Good point. I'll let you know even more in a day or so. I tried the all Copper coins in pure, chemical supplied Acetone. Yesterday at approximately 5PM central time I emersed a cent, nickel, 2 dimes and a quarter in Walmart paint department type of Acetone. However, no sun light available here. Freak snow storm hitting the chicago area right now. I'll post results of this as soon as the snow clears.

 

Carl,

Thank you for your insights and experimentation. This is a very informative thread thanks to your efforts.

 

Just one more probably by now boring post about the usage of Acetone on coins.
On April 10, 2007 @ 5:00PM I emersed 6 coins in a beaker full of Acetone. This is Acetone recently purchased from Walmart Paint department in a metal can. I covered the beaker so as to stop evaporation and left it on a window ledge inside my garage so it would be in some light.
April 11, 2007 @ 5:00 PM I moved the beaker with the coins to a location outside next to my garage and in direct lighting. Still no sun but kind of clearing out.
April 12, 2007 @ 3:00 PM I removed all the coins from the beaker and placed on a redwood patio table to dry. No rinsing of any kind.
April 12, 2007 @ 3:30PM I brought all coins inside the house, placed on a paper towel, turned on a bright lamp, got out magnifying glasses. NOW the results.
1972D Lincoln Cent from previous experiment with the green crud on it and still there. Does not appear to have been cleaned at all.
1988D Jefferson Nickel was scratched, dented, dirty and now appears to be much cleaner. Dents and scratches more noticable.
1905 Liberty Dime that was to worn to see any Mint mark and a large area on the obverse with dark black discoloration remains the same on the obverse but a dark area now appears on the reverse.
1977 Roosevelt Dime was just very dirty as if found in the ground. Now the obverse is new looking but the reverse has a dark area similar to the 05 Liberty Dime.
1980 Washington Quarter was just well worn and slightly old in appearance. Now shines like a coin from the Mint. Acetone worked well for this one.
Feeling a little irritated about the Dimes I placed them both in Vinegar for a few minutes. No change. Then I added some Lemon Juice to that and rubbed both coins. Still no change on the 05 but the dark area on the reverse of the Roosevelt Dime now turned Copper colored.
Still my summation is coins should not be cleaned but obviously a dip in a decent or better grade of Acetone will not hurt them. Oviously even if forgotten for a few days.
Of course in different climatic areas the air, amount of light, gravity, etc., may bring other results.

 

Just one more follow up in case anyone is interested. All coins from the last experiment have been sitting on a kitchen table since my last post. Never rinsed or washed and all look just like they did previously. Obviously even the Walmart Acetone did not distroy them.