> Message text written by Edward Meyers
> >I have some metol in an unopened container for
> about 15 years. Other chemicals, as well. Ed
> <
>
> Me too, and a large beautiful jar of pyro (!) that must be seventy or so.
>
> Terry King
>
You know, it really depends on the particular chemical, but generally
speaking, heat and humidity hasten the compounds demise. I have many jars
that are about twenty years old, and can say as a rule of thumb if they
have not changed their appearance they should be fine- decomposition
almost always involves a change in appearance. The only compound that I
have that seems to have changed is some pyrochatechin which has gone
greyish, but I received it as a gift and not in its original container.
John