Products / pH Indicators


C.A.S. No. 125-20-2
M.F. C28H30O4
M.W. 430.54gm/mole


Transition range pH 9.3-10.5
Solubility 0.1 % (95% EtOH) Clear solution
Absorption maximum (0.1N NaOH) ?max 592-596nm
Absorptivity (A1%/1cm at 0.1NNaOH, at ?max) >1000
Loss on drying (110°C) <1%

Chemical Name


InChI Key



Soluble in acetone, alcohol, and dilute aqueous alkali. Insoluble in water.

Product Description:

Thymolphthalein is a white powder that is dissolved into a clear, colorless liquid when added to isopropyl alcohol. An acid base indicator, it turns a brilliant magenta color when it comes in contact with basic solutions like sodium hydroxide or ammonia hydroxide, and returns to clear when an acid is introduced to the solution, balancing out the pH. Thymolphthalein is an acid-base indicator which is colourless in acidic form and deep blue in basic form. Acidic form retains hydrogen on each hydroxyl group.


Thymolphthalein acts as pH indicator, as reagent for blood after decolorizing the alkaline solution by boiling with zinc dust. Solubility Soluble in alcohol, acetone and also soluble in dilute alkalis. insoluble in water.The solubilization effect of 14-s-14 series dicationic surfactants is quantified via spectrophotometry using a thymolphthalein hydrophobic indicator.Also used to model communicable disease transmission and the importance of lab cleanliness.Thymolphthalein was suitable as indicator during titration of hyamine hydroxide.It is suitable in preparing disappearing ink.

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