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I want to determine the extinction coefficients of Fe2+ and Fe3+ in glass.

There are literature data (e.g. Weyl's book "coloured glass"), so I know what kind of curves I should expect. As I am studying a slightly different soda-lime-silicate system, I want to recalculate the curves.

I have glasses with different Fe2+/Fe3+ ratio and total iron concentration [Fe].

I have measured the absorbance of two glasses and I have solved a simple two equations system starting from Lambert-Beer law: A = Ʃ εCd

where A is absorption, ε is the extinction coefficient, C is the concentration and d is the thickness of my glass.

Unfortunately, I get negative values in one of the two extinction coefficient curves. Obviously, this doesn't make sense.

Anyone sees what is wrong in my reasoning? I can't figure it out.

Thank you very much in advance,

Mark

PS For a close look at the system I have made, see the attachment (.pdf)

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# Determine extinction coefficients in glass for Fe2+/Fe3+

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