I was dipping some coins in acetone to remove some black sludge on an off center misaligned die penny I found. I have a little knowledge about chemistry and I was wondering... in the lab in addition to using acetone to clean glassware if something still wouldn't come off still we would use other "stronger" organic solvents like hexane or chloroform. I am thinking that a chloroform dip would do a much better job at restoring a coin than acetone without attacking the metal or most oxides that form toning like a strong acid would... has anyone tried this? Also has anyone tried lightly heating the acetone? PSA: Don't even think about trying to heat acetone unless you know exactly what you're doing, acetone starts to vaporize just above freezing (that's why it makes your fingers feel so cold it almost feels like burning as it evaporates so fast) making it very easy to ignite if heated too much or with the wrong equipment.
Please, do not ever heat acetone! I don't care what you think you know, you are flirting with an explosion if you heat acetone. Getting crud off a cent is not worth the destruction of a fire or explosion and the death or injury that can occur. Additionally, you may want to try Blue Ribbon or Care if you need other solvents, but again I wouldn't recommend hexane or chloroform for not only health reasons, but for disposal, too. PS: PhD in molecular and cellular biology and biochemistry with loads of experience as the head of an analytical chemistry depratment at a major chemical company.
Is hexane dangerous? Answer: According to the Material Safety Data Sheet, Hexane is very dangerous. It is Harmful, Dangerous to the Environment, and Highly Flammable. Stability: Hexane is stable, however it is incompatible with oxidizing agents, chlorine, fluorine and magnesium perchlorate. It also readily forms explosive mixtures with air and has a low flash point. Toxicology: Hexane may cause impaired fertility and CNS Depression. It is an irritant and it is harmful if inhaled. Prolonged exposure may also cause serious health damage. Environmental Information: Hexane is harmful in the environment and may cause long-term effects. Personal Precautions: One should wear safety glasses and a lab apron. Appropriate ventilation is needed such as a fume hood. All sources of ignition need be removed from the working area. Chloroform is very dangerous Chloroform is no longer available to the general public and for good reason. What would you be using it for? There are usually safer alternatives. Despite the fact that we see people getting knocked out by Chloroform on TV/Movies all of the time. You should know that it is a pretty dangerous level. If you can even smell chloroform in the air you are actually above the legal exposure limit for chloroform. Any waste chloroform must be treated as a highly toxic waste. FROM WIKIPEDIA: As might be expected from its use as a anesthetic, inhaling chloroform vapors depresses the central nervous system. It is immediately dangerous to health and life at approximately 500 ppm according to the United States National Institute for Occupational Saftey and Health. Breathing about 900 parts of chloroform per million parts air (900 parts per million) for a short time can cause dizziness, fatigue, and headache. Chronic chloroform exposure may cause damage to the liver (where chloroform is metabolized to phosgene) and to the kidneys, and some people develop sores when the skin is immersed in chloroform. Animal studies have shown that miscarriages occur in rats and mice that have breathed air containing 30 to 300 ppm chloroform during pregnancy and also in rats that have ingested chloroform during pregnancy. Offspring of rats and mice that breathed chloroform during pregnancy have a higher incidence of birth defects, and abnormal sperm have been found in male mice that have breathed air containing 400 ppm chloroform for a few days. The effect of chloroform on reproduction in humans is unknown. Chloroform once appeared in toothpastes, cough syrups, ointments, and other pharmaceuticals, but it has been banned in consumer products in the United States since 1976.
I guess I wasn't clear enough, by lightly heating I was more referring to something more along the lines of like a controlled 100F warm water bath, outside, away from any source of ignition, not actually putting acetone on a heating element or anything like that that would take it past it's 130F boiling point. That would be suicidal I agree. That's why I bolded "lightly".
There is no need to use heat with acetone, as its purpose with coins is to dissolve organic material and an increase in time will do as well as an increase in temperature. It can not repair or restore any previous condition to the metal, nothing really can bring it back to what it was before. Hexane, even in a lab should be used with great care. Old time stamp collectors and "paper" collectors used hexane to determine watermarks, although it is only drops, and Ronson type lighter fluid ( naptha) is easier to buy and as effective, as neither damage the paper. Chloroform should be limited to the few organic syntheses that require it and only in a controlled lab situation. Look up Verdi-Care ( BadThad ) also as it has a different composition than products like Blue Ribbon and MS-70. IMO. Jim
Hexane gets metabolized into a particularly nasty product, 2,5-hexanedione. Oddly (and unfairly) enough, it's much worse if you're exposed to acetone at the same time, even though acetone by itself is relatively safe. Detailed summary (warning -- pretty heavy going if you aren't a biochemist) I'd rather use heptane, which isn't nearly as toxic, and has a lower vapor pressure as well. But it's probably harder to find. Chloroform should be right out. It's pretty toxic, and I'm generally opposed to using chlorinated solvents on reactive metals anyhow. I doubt that heating an acetone bath would make much difference -- the difference between room temperature and acetone's boiling point just isn't that great. You could use MEK, I suppose, but its BP isn't much higher. If you really want a non-polar solvent that can be used at a high temperature, you could always try a paraffin bath. Just not with any of my coins, please.
Heating acetone is not a particularly good idea, aside from being dangerous (as people have said) I don't think any stripping effect would be accelerated that much. The chloroform is an interesting idea, but chloroform does tend to be somewhat dangerous (although it really does smell good, kind of like juicy fruit gum) and I am not sure what a chlorinated solvent would do to coinage metals. Another possibility would be methylene chloride which used to be found in paint strippers along with methyl alcohol and sodium hydroxide. Safer to stick to materials available to collectors.
