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<p>[QUOTE=&quot;-jeffB, post: 3253659, member: 27832&quot;]I think you&#039;re off-base (sorry) here.</p><p><br /></p><p>1 is questionable -- humidity catalyzes <i>some</i> oxidation reactions, notably &quot;rusting&quot;, and light can drive <i>some</i> oxidations, but often just by raising the temperature.</p><p><br /></p><p>2 is flat-out wrong. Acetic acid is <i>not</i> an oxidizing agent, not any more than water is. (Sure, a strong enough <i>reducing</i> agent will take oxygen from acetic acid, but the same is true of acetone, or water.) Mostly, it&#039;s just an acid, and not a very strong one. (Oh, and &quot;amino acids&quot; is a red herring. They have nothing to do with this chemical system.)</p><p><br /></p><p>If acetone really <i>is</i> being converted to acetic acid, it&#039;s because the acetone is being <i>oxidized by air</i> in the presence of copper, light, and humidity. It&#039;s a very harsh oxidation, if it&#039;s enough to tear off one carbon from the molecule&#039;s backbone. I don&#039;t know what level of illumination they used in the cited study, but I&#039;ll bet it was a lot stronger than direct outdoor sunlight, which in turn is a lot stronger (because it includes UV) than direct sunlight coming in through a window, which in turn is literally ten to a hundred times more intense than normal indoor lighting.</p><p><br /></p><p>Even if you do get acetic acid, that by itself isn&#039;t going to attack copper. It needs an <i>actual</i> oxidizing agent. Copper is lower on the activity diagram than hydrogen, so it isn&#039;t attacked by a simple acid. Nitric acid does attack it, because that <i>is</i> an oxidizer as well as an acid.</p><p><br /></p><p>What even dilute acetic acid <i>will</i> do, slowly, is dissolve copper oxide, that brown layer that makes the copper look &quot;normal&quot;. It&#039;s not <i>reducing</i> it (removing oxygen from it), it&#039;s <i>turning it into a soluble compound</i>, copper acetate, and washing it away. <i>That</i> will leave the copper &quot;looking funny&quot;.</p><p><br /></p><p>But I suspect what <i>really</i> happened with those copper coins Doug and others have seen is that the acetone, pure and uncontaminated, removed a layer of foreign material that <i>looked</i> like oxidized copper (producing an immediate color change), or removed a layer that was protecting a completely <i>unoxidized</i> copper surface, which quickly turned once it was exposed to air (and humidity and whatever else that air carried). But, of course, I wasn&#039;t there with a fully-equipped lab, so my <i>opinion</i> is only that.[/QUOTE]</p><p><br /></p>

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