My Glycin is stored in amber glass containers which are
kept in a cabinet around 21 deg. C under low humidity conditions.
Tri-Ess Sciences is a good source of those bottles. I've scores of
them all equipped with the Polycone or Polyseal caps. I wonder how
many who work in the darkroom are as carefull as myself in the sealing
of their bottles. I take chemical longevity reports very guardedly.
As for glycin and for that matter phenidone, I wonder if those two in
particular are in themselfs unstable. There are many reports of the two
going bad in the bottle, so to speak.
If they are not unstable in themselfs, and they go bad within a few
years, it"s likely due to the glass bottle having a leaky cap. Dan