Identifying chrome tanned leather

Recently I bought 12 calfskins which are vegetable-tanned. At least
that's what the vendor claims. Working with the leather (paring,
gluing) it seems to me that is is at least a different type of
leather and I wonder if it is mineral retanned with chrome.

Is there a *simple* way to determine whether there's chrome involved
in the tanning of this leather? So, no spectrometry etc. but a test
which can be done "at home". I know of the bluish/grayish layer
between the grain and flesh side but that is only very faint (still
it is there...). I've also tried a simple shrinkage test (chrome
tanned leather normally has a higher Ts but both samples (old and
new) shrank below 100 deg C). Any tips are very much appreciated,

Cor Knops
Knops Boekrestauratie
Restoration and Conservation of Books and Paper
Groenstraat 8
6151 CS Munstergeleen
Netherlands
+31 46 4200024
+31 46 511822
Fax: +31 46 4110180

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                  Conservation DistList Instance 12:13
                 Distributed: Wednesday, July 29, 1998
                       Message Id: cdl-12-13-007
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