Leaf chlorophyll extraction

lee hadden hadden at wingate.edu
Fri Mar 14 13:46:52 EST 2003


David--

I'll hazard a guess at a possible reason [and look forward to any
appropriate correction]  Since alcohol acts as a coagulating fixative,
it may be that the sudden and extensive coagulation of peripheral
protoplasm by 90% alcohol creates more of a permeability barrier to
diffusion of the chlorophyll than the 50% does.  The 50% alcohol fixes
more slowly and may allow time for chlorophyll to be extracted before
much protoplasm [and possibly chloroplast stroma] have coagulated to
the point of retarding chlorophyll extraction.  Just my first thought,
but it seems reasonable.

Lee Hadden


David Hershey wrote:

> A student observed that geranium leaves to be used for
> starch testing decolored better in 50% isopropyl
> alcohol than in 90%. The alcohol was heated in a
> boiling water bath. All the other variables were the
> same.
>
> Does anyone know why 50% alcohol would be better for
> removing chlorophyll than 90% alcohol?
>
> David R. Hershey
>
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