[BROe]

I'm looking into purchasing Potassium Permanganate, KMnO₄, and after reading the msds sheet for the chemical have a few questions that were left unanswered. Normally I would just go to google for this however I was unable to find answers to either, so I turn to this forum.
Firstly, is there a shelf life for Potassium Permanganate?, as I don't want to purchase it, use it for a few reactions, let it sit for a few months and find out later that it's all decomposed.
Secondly, after reading the msds for the commercial KMnO₄ referred to as "pot perm" I discovered that the purity can be from 60-100%. However the commercial brand is cheaper than lab grade, which is doubtless of a much higher and smaller purity range. So is there a significant enough difference in the purities to where the use of the commercial brand would effect the outcome of my experiments?

[Arkcon]

We might be able to give you some hints, if we knew exactly what your planned experiments are.

[BROe]

Of couse, my mistake. Initially I plan to do the common reactions with the permanganate, such as Elephant toothpaste, it's reactions with Glycerin and sugar water, and it's reaction with NaOH and sugar for it's several color changes as the oxidation state decreases. After this I'll want to mix it with other salts to explore different permanganate compounds.

[Arkcon]

I think even the 60% purity would work just fine for those demonstrations.  My lab's potassium permanganate, for qualitative analysis, has a manufacturer shelf life of at least two years, and I'm pretty sure your would last at least that long, with reasonable storage, i.e. not too humid, not too hot.

[Borek]

not too humid, not too hot.

And not too bright.

[Mercuric cyanide]

You might want to recrystallize one or more times, which, depending on what the impurities are, could get it to 95-99% easily.

[Za_fantasia]

Once mixed with water the shelf life is 3 days. Even if kept in the fridge.

That is mainly with small amounts, I don't know how things work with larger amounts of both/either water or PP.

[Borek]

Once mixed with water the shelf life is 3 days. Even if kept in the fridge.

Definitely much longer.

Several days can be enough for the observable change of the concentration - high enough you may need to restandardize the solution if used as a titrant. But whenever you need approximate concentration only, solution is reasonably stable for weeks or even months (especially if kept in the dark bottle).