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I was working in the lab preparing Tollens’ reagent. When I came back home, I observed that my fingertips were brown, and I tried to wash it with soap several times but it didn't work.

It has been a day and they don't seem to go.

What may have been the reason? Is it permanent and how can I get rid of it?

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    $\begingroup$ Let that be a massive wake-up call. The three things that matter most in a chem lab? SAFETY, SAFETY, and SAFETY. Have a safety plan and know how you are going to properly dispose of all waste before you start any experiment. We don't about safety nearly enough on this site. $\endgroup$ – MaxW Sep 22 '16 at 13:27
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    $\begingroup$ The stain will wear off your fingers in a few days. Just wait... $\endgroup$ – MaxW Sep 22 '16 at 14:06
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    $\begingroup$ @JimGarrison - I'd take some exception to your example. It is entirely possible to get exposed in some way or by some chemical where the problem is yet unknown. That is a small risk associated with being a chemist. What is STUPID is to ignore the science that we do know. Cyanide is toxic. Rubbing it on your fingers and dying isn't an accident, as in the case of Dr. Wetterhahn, it is plainly just STUPIDITY. 99+% of "accidents" in a chemistry lab could be avoided with a proper consideration for known safety factors. $\endgroup$ – MaxW Sep 22 '16 at 18:28
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    $\begingroup$ Of all things that can leave long-lasting marks on your skin, silver is probably the least harmful. In a way, it might even do you a little good because of antimicrobial activity. Your attempts to get rid of it, though, might be REALLY dangerous. Just leave it alone, or you'll end up in a textbook, and not quite in the role of Tollens or Fehling, but rather like Karen Wetterhahn or Sheharbano Sangji. $\endgroup$ – Ivan Neretin Sep 22 '16 at 19:24
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    $\begingroup$ @MaxW I made a small edit to your comment because I removed the comment you were replying to. $\endgroup$ – jonsca Sep 22 '16 at 22:40
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The stains are due to silver nitrate, the reactive portion of Tollens’ reagent. It is very prone to reduction to metallic silver.

If you got it on your hands (a clear signal you weren’t wearing gloves when you should have been) it will create small silver particles in your skin — this is why it won’t wash off. Since the particles are small, they don’t exhibit the classical metallic characteristics (looking silvery, reflecting etc).

Don’t worry, they will grow out within a week’s time or so, due to your skin renewing itself.
And wear gloves next time.

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