On Wed, 10 Nov 1999, Sarah Christo wrote:

>   Thank you for the reply.  I'm making solutions and have two questions.
>Can the acidified potassium permanganate be made up as a stock solution
>with the acid or should the acid be added just before use?

    It's usual to add the sulphuric acid before using. I do not know
    if a stock solution is indefinitely stable but would guess that
    it is.

>   Also, just as a curiosity, (since there has been a discussion going on
>Alcian Blue), I have a variance in Alcian blue solutions made.  I have
>many shelves of old dyes and picked what I thought was the newest dye to
>make up the Alcian Blue pH 1.2.  This was a Sigma dye from 1985.  It
>formed a precipitate so I filtered it and it is a pale blue, weak looking
>solution.  I then tried a Chroma Alcianblau 8GS from 1971, and this did
>not precipitate like the other (only slightly) and is filtering to make a
>much stronger looking darker blue solution.  These two dyes in powdered
>form also look different.  The Sigma is a finer powder, darker blue, the
>Chroma is a more granular consistency and a lighter blue.  Any thoughts on
>which one of these would be better to use?  I plan to run a control
>through on both of these first of course, but was curious about the
>differences.   Thanks, Sarah

     I have had similar experiences. Alcian blue does go off in
     the solid state. The insoluble product is probably copper,
     phthalocyanine, which is the stuff that's retained in
     stained sections when the solubilizing isothiouronium groups
     are split off in the course of dyeing. Moisture probably
     accelerates deterioration of alcian blue powder, and ammonia
     fumes would insolubilize it very quickly. I've got just one
     old bottle of AB that's still OK, and that is from Edward
     Gurr (London, England), simply labelled "Alcian blue (no
     letters), Michrome No. 34);" no CI number and, of course,
     not BSC certified. It is certainly more than 30 years old.
     AB bought from N. American firms in the 1970s has all had to
     be chucked out.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1