Shelf life of Campden/SMB/PMB

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Earl_Grey

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I am on a quest to find out what the shelf life of these chemicals are.

I have an old bag of campden tablets and an old bag of potassium metabisulfite powder. These bags are easily 2+ years old and stored in the garage which gets hot/humid etc, probably not the best conditions.

According to this site:
Potassium metabisulfite
The shelf life of PMB is 6 months at 25C and 45% humidity.

Are we supposed to store these in the fridge? Even then whats the shelf life then? How can one tell if the chemicals are still good? I've read to smell it and see if it smells of sulfur but is there anything more scientific? My LHBS buys these chemicals in big bags and then repacks into smaller bags so I'm not sure if I bought a new bag if that bag would be "fresh".
 
Interesting in that I treat my water with PMB to eliminate the chlorine /chloramine. Recent batch has developed a phenolic flavor. I know my PMB is at least a couple years old. Probably time for new.
 
You guys know that the Internet is the source of all knowledge...but my limited research after seeing your posts indicate that the shelf life is either between a few months, or 50+ years...haha. I replace mine annually...which is a tremendous waste I"m sure...but $4 is $4.
 
You guys know that the Internet is the source of all knowledge...but my limited research after seeing your posts indicate that the shelf life is either between a few months, or 50+ years...haha. I replace mine annually...which is a tremendous waste I"m sure...but $4 is $4.

I think this is going to be my new plan too. Keep them in a sealed bottle in the freezer.
 
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