Question
Sat July 09, 2011 By:

do each pH paper have their own reference chart

Expert Reply
Mon July 11, 2011
In case of indicators, color change occurs over a range of hydrogen ion concentrations. This range is termed the color change interval. It is expressed as a pH range. So there is no specific colour associated with any pH value its like a spectrum having a range of colours hence at pH 14 we can observe dark blue colour or greenish-blue colour both are correct. For example:
Poirrier's blue 11.0-13.0 1 drop 0.1% aq. soln. blue violet-pink
Trinitrobenzoic acid 12.0-13.4 1 drop 0.1% aq. soln. colorless orange-red
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