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    Hi,

    I understand that colorimetry can be used to deduce the concentration of a certain solution of a transition metal complex using a calibration curve. However, various diagrams show a filter between the white light source and the coloured solution. Online sources say this filter is the complementary colour to the colour of the solution. Why is this necessary? Surely if the solution is going to absorb the complementary colour anyway then a filter is pointless?

    Can someone explain the purpose of the filter to get rid of my confusion?

    Thanks!
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    (Original post by DhylanP - CRGS)
    Hi,

    I understand that colorimetry can be used to deduce the concentration of a certain solution of a transition metal complex using a calibration curve. However, various diagrams show a filter between the white light source and the coloured solution. Online sources say this filter is the complementary colour to the colour of the solution. Why is this necessary? Surely if the solution is going to absorb the complementary colour anyway then a filter is pointless?

    Can someone explain the purpose of the filter to get rid of my confusion?

    Thanks!
    The filter ensures that light of the correct wavelength range passes through the solution for absorption.

    It is this that is to be absorbed and the detector can then compare the absorbance with that of the reference cell.

    There is no interference in the detector and its sensitivity can be ramped up. If all wavelengths were passed through, then the difference in absorbance between the reference and sample would be much less in terms of percentage.
 
 
 
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