Colorimetric Determination of Ph

2799 Words Sep 11th, 2013 12 Pages
------------------------------------------------- Date Due: July 25, 2013
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Date Submitted: July 25, 2013
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EXPERIMENT NO. 4
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COLORIMETRIC DETERMINATION OF pH
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Abstract
This experiment examined the result of the various color indicators combined with different buffer solution,
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Bromocresol Purple A brominated acid dye of the sulfonephthalein series derived from ortho-cresol that is obtained as a pinkish crystalline powder and is used as an acid-base indicator. It is a substituted triphenylmethane dye (pKa 6.3), practically insoluble in water but soluble in alcohol and dilute alkalies; used as an indicator of pH (yellow at pH 5.2, purple at pH 6.8).
Thymol blue Thymol blue (thymolsulphonephthalein) is a brownish-green or reddish-brown crystalline powder that is used as a pH indicator. It is insoluble in water but soluble in alcohol and dilute alkali solutions. It transitions from red to yellow at pH 1.2–2.8 and from yellow to blue at pH 8.0–9.6.
Phenol red A bright to dark red, slightly water-soluble crystalline dye used as an acid-base indicator and to test kidney function and renal blood flow. Also called phenolsulfonphthalein.
Phenolphthalein
Phenolphthalein is a chemical compound with the formula C20H14O4 and is often written as "HIn" or "phph" in shorthand notation. Often used in titrations, it turns colorless in acidic solutions and pink in basic solutions. If the concentration of indicator is particularly strong, it can appear purple. In strongly basic solutions, phenolphthalein's pink color undergoes a rather slow fading reaction and becomes colorless again.
Bromocresol Green Bromocresol Green (BCG) is a dye of the triphenylmethane family (triarylmethane

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