# How long can iodine bottle left open? Can it go bad sooner than expiration date?

I have bought iodine about a year ago but the bottle cap got damaged during the transportation and it leaked all over the package, but I have decided to keep it anyway. Unfortunately I did not use it to anything and it was just sitting on my shelf with cracked cap with about a one millimetre sized hole.

I wonder if it could go wrong and now it's useless. As far the expiration date, it's still not expired, but that's probably when the bottle is fully sealed.

So is it still safe to use if needed or I can return it to the drug store so they can safely dispose it?

Content for 100ml: iodopolyvidonum 7,5g with 10% content of Povidone-iodine (M.h. 40 000)

Thank you

Iodine itself has a comparatively high vapor pressure, ~40 Pa at room temperature, so iodine solutions, e.g. tincture of iodine (iodine in ethanol/water), lose iodine by evaporation (well, by sublimation, from the solid). This just means that the strength of the antiseptic is reduced if left open, not that it has not "gone bad," in the sense of being dangerous.

For povidone iodine, $$\ce{C6H9I2NO}$$, the vapor pressure is far lower, ~1.3 Pa at room temperature, so the rate of loss of iodine would be far slower. Again, though the antiseptic will slowly lose potency, it does not "go bad". If the color looks noticeably lighter, I'd discard it to get a new bottle.

That said, iodine is not a perfect bactericidal or fungicide. for example, Pseudomonas bacteria have been found in production systems for commercial iodine antiseptic. Not to worry, though, as long as povidone iodine is used according to directions. Just cover the bottle with material that does not react with iodine. Note that plastic food wrap and polyethylene bags allow iodine vapor to go through slowly, so use a few layers if that's your choice for a cap.

• Thank you, I did not expect to get such a detailed answer. I have learned something new. Thank you – Erik Kubica Feb 22 at 8:13

A solution of iodine antiseptic is a medical item that is used for improving health. There are two ways to treat your cracked cap.

#1. If you inspected the bottle in the drug store before you bought it, you would not buy this bottle. Almost all over-the-counter medicines have warnings: Do not use if the safety seal is broken. So, out of utmost caution, do not use this iodine, because it might be contaminated (even tho you are the only one who could have contaminated it). Look at it this way: you bought a bottle of iodine solution, you had its potential usefulness for a year to keep your skin abrasions antiseptic (even tho you did not have the need to use it). It can be considered to have served its purpose usefully; get a new bottle and be more careful.

#2. Being the cheapskate that I am, I would examine the bottle: has the liquid level dropped and dried out? Is it gooey so as to be difficult to apply? If not, it might be OK to keep and use. On the other hand, a cracked lid is an invitation to disaster - if the bottle gets knocked, it will leak - probably onto the item you just laid down, which will, of course, be very important and/or delicate. To avoid catastrophes of this sort, dispose of the iodine solution. You will feel more secure. Get a new bottle.

Or, get a tube of antiseptic ointment, which will have less tendency to spill, unless you step on it.

• Thank you for the easy to understand answer even for someone who does not have much in common with chemistry. As far the #1 goes, I have bought it online, the delivery man messed up and I got my money back and I was thinking it might be useful someday. For the #2 Nope, it did not dry out. Everything looks perfectly fine but I am not a chemist nor know anything about medicine, so that was the reason I came to seek more professional insight. Considering DrMoishe gave more professional answer and this is stackexchange, I have accepted his answer, but I am glad for yours too. Thanks again :) – Erik Kubica Feb 22 at 8:21
• BTW, please don't consider this medical advice in any way... we're just commenting on the state of the chemical, not it's usefulness for any purpose. – DrMoishe Pippik Feb 22 at 17:28