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From:Jim Elsam <> (by way of histonet)
To:histonet <>
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Rose Clarke asks:

Does anyone have a method for Grocott without using Chromic Acid?


Chromic acid is a singularly nasty chemical which we would all do well
to avoid. The Grocott method is quite similar to PAS in that you
"oxidise" to produce aldehyde groups which are then detected with either
Schiff's or methenamine silver.

Better chemists than I will, hopefully, explain the different effects on
sugar molecules produced by chromic and periodic acids but... you can
substitute periodic acid for chromic acid although the sensitivity may
not be quite the same.

Grocott will produce better contrast than PAS but not if you overcook it
so that all the collagen and stuff comes up. This unwanted staining is
directly related to incubation time in silver solution so you have to be
a good judge of section coloration to avoid it. "Lemon yellow" is often
quoted and any sort of brown is too dark.

Good luck
Jim Elsam
HTEQA Services

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