[Histonet] Paraformaldehyde.

[Rittman, Barry R]

I agree totally with Geoff.
While it sounds good - it is impractical to store most chemicals under inert gases. Would be nice to store dyes and stains so that they did not become oxidized etc.
 
Might I suggest that you weigh out smalkl aliquots and place them in glass screw capped tubes and then keep these in a tightly sealed jar in the refrigerator. That shoudl solve the problem.
If you are concerned about mixing then you might want to consider purchasing selaed glass vials of prepared paraformaldehyde solution. 
Not sure who sells that now but it used to be Ladd Industries.Glutaraldehye solutions in sealed vials also available.
While these may seem expensive foe\r what they are - it does cut down on your time and effort and is safer than making solutions yourself. Additionally you could tell your supervisor that the most expensive item in the lab is (and should be) your time.
Barry