On Sat, 28 Jul 2001, Sunil Thomas K wrote:

> I have a question regarding chrome alum-gelatin used
> for subbing. It gets very viscous when referigerated
> (difficult to pour out from the glass bottle. 
> Is this solution warmed before slides are dipped?

A smart observation, Sunil Thomas K !
Chrome-gelatin solutions must be used soon after
making. They cannot be stored in a fridge or
anywhere else. They cannot be diluted either.

Try this experiment.  Make a chrome-gelatin solution
and put 1 ml of it into a test-tube or similar vessel.
Prevent evaporation with a bung, and after a few days
add 10-20 ml of warm (about 40C) water. Shake well and
observe. The gel, in which protein molecules are 
cross-linked by Cr atoms, cannnot be dispersed or
dissolved in the water.

Chrome gelatin solutions quickly become infected
so they should be used right away and not stored.

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