Hi,
    There is a quick fix for this situation. It will help with inventory and is
cost effective. Try to anticipate how much stain you actually use. Reasonably,
try to plan to have enough to last less than 5 years. This way there will be
less waste if you decide to discard the chemical to buy new.
Amos Brooks

"J. A. Kiernan" wrote:

> On Tue, 21 Mar 2000, Marlene F. LEFEBVRE wrote:
>
> > Dear Friends. We are attempting to become GLP compliant, and was wondering
> > how others handled expiry dates on the dry powder biological stains which
> > in most part are very stable.  Help would be appreciated. Thanks Marlene
>
>   Studies done at the Biological Stain Commission's lab have shown that
>   dyes are extremely stable in dry powder form. See
>   Emmel, V. M. and Stotz, E. H. 1986. Certified biological stains: a
>      stability study. Stain Technol. 61: 385-387.
>   More recent investigations (reported at the Commission's annual
>   meeting 2 years ago, but not otherwise published) confirmed these
>   observations and extended the time for another 10 years.
>
>   Thus, you could safely put an expiry date 10 years in the future
>   on solid stains. The only exception might be alcian blue, which
>   can sometimes change unpredictably into insoluble copper
>   phthalocyanine. I don't think this change is related to time
>   of storage, but suspect it is due to factors like dampness
>   or accidental exposure to ammonia fumes.
>
>  John A. Kiernan,
>  Department of Anatomy & Cell Biology,
>  The University of Western Ontario,
>  LONDON,  Canada  N6A 5C1