Re: chrome-alum gelatin

From:"J. A. Kiernan"

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.

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

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