[stdacet]

The expiration date mentioned on 3 M Potassium Chloride reagent is about 3 year. Perhaps the manufacturers add some preservative to prolong the shelf life.
However when prepared in the laboratory from solid potassium chloride, what will be the approximate shelf life/ expiration date?

[Arkcon]

This is a very common question, which unfortunately has no easy answer.

http://www.chemicalforums.com/index.php?topic=29560.msg112551#msg112551

I don't know if there's a preservative or not in commercial 3 N KCl, of if just its concentration keeps it microbial free.  I have prepared saturated KCl, and left it in a jar in my basement, it soon grew water mold.  Maybe just by virtue of being in a lab environment, it keeps better.  Or the manufacturer just expects you to use it quickly and throw it away when it goes bad.