Re: chrome-alum gelatin

From:Connie McManus


This is an interesting experiment, but I have never seen where my gelatin
solution cannot be dissolved. I do it every day by putting it in my
waterbath. I works Jim Dandy-- I don't have sections falling off.
Furthermore, I have never seen any kind of contamination, fungal or
bacterial.  With all due respect, John, my experience does not mesh with
what you have said, so, below, are some questions about your experiment.  

At 03:54 PM 7/30/01 -0400, J. A. Kiernan wrote:
>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.

What is the connection between this and Sunil Thomas K's observation that
the solution is viscous when refridgerated?  That is the nature of cold
gelatin in my experience. As soon as the gelatin comes to RT, it is liquid
--- well, less viscous.  Put it back in the fridge and let it come to that
temp, voi la, viscous gelatin again.

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

I thought the reason for adding the chrome in the gelatin solution was to
prevent contamination (or infection).  I have used gelatin solutions
without it and they DO become contaminated no matter how aseptic you treat
them.  I have never ever had any problem with this since adding chrome
sulfate to my gelatin (keep in mind, I never allow anything non sterile to
touch the gelatin, either).

My last question is...are we talking about the same formula?  My formula is
1.5 g gelatin in 300 mL DI water and 4 mL 4% chromic sulfate, autoclaved
for 15 minutes on a lq cylce and stored in a tightly sealed container.  I
have always called this Chrome Gelatin (the person who clued me in to this
was from Bern, Switzerland and that's what she called it).

seeking enlightenment *g*
Connie McManus

Veterinary Diagnostics Lab

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