Campden Tablets - quick question.

[NWC]

Do campden tablets go off ?
I know they have a sell by date, but how critical is it?
Thing is, I used a crushed one when I racked some wine recently, and now it tastes differerent.
Is this just the tablet doing its thing, or have I tainted my wine?
Thanks

[vacant]

I'm not a chemist but I think it won't go off. Opening/closing the container means a small amount of water vapour may get in over time so you may end up with some sodium bisulphite. I believe it is when the campden tablet (sodium metabisulphite) reacts with acidified water that sulphur dioxide is given off (i.e. neutralising chlorine, which is what we use it for).

[Parva]

I'd agree. I'm still using a bottle of 40 Boots Campden tablets bought for 28p (price sticker still on) from circa 1985! I did a few kit brews back then then quit until recently taking the hobby back up with all grain brews.