Products / pH Indicators


C.A.S. No. 40070-59-5
M.F. C23H20Br2O5S
M.W. 568.29gm/mole


Dye Content (by Spectrophotometry) >95%
Transition Range pH 5.7-7.4
Solubility 0.1% (95% EtOH) Clear solution
Absorption maximum (pH 5.7) ?1max 432-437nm
Absorption maximum (pH 7.4) ?2max 613-615nm
Absorptivity (A1%/1cm at pH 5.7 at ?1max) 300-330
Absorptivity (A1%/1cm at pH 7.4 at ?2max) 500-540
Loss On Drying (110°C) <3%

Chemical Name


InChI Key



Soluble in alcohol and aqueous solutions of alkali; sparingly soluble in water. Soluble in ethanol, ether and alkalis. Slightly soluble in water.

Product Description:

Xylenol blue, shown the double working ranges of utility with those of thymol blue. The pair of indicators thus share with certain other pairs of homologous indicators the property of anomalous unshifted PH ranges. Advantage was taken of this property in the case of xylenol blue to obtain a solution of twice the intensity of thymol blue. When the PH range of The bromo-derivative of xylenol blue was investi-gated in the same manner as that of the unbrominated indicator, and compared with bromothymol blue in identical concentrations and strengths of indicator in buffer solutions of PH6*0-7*6, the series in each case was similar. The analogy of xylenol blue with thymol blue in-respect of range of PH is thus continued on bromination.


Near Neutral pH Indicating properties of Bromoxylenol Blue are used in optical lenses, diagnosis of multiple diseases, sol-gel matrix, determination of drugs, lubricants, toys, paints, microorganism detection, cosmetics and food storage and shelf life indication.The relationship between the activity of hydrogen ions [exactly hydronium ions, H(H2O)n+] and concentration of a solution is fundamentally important to determine the extent of a chemical reaction, as it affects the equilibria and kinetics of a wide variety of chemical and biochemical reactions. The hydrogen-ion activity refers to the effective concentration of unassociated hydrogen ions, the form that directly affects physicochemical reaction rates and equilibria. The symbol, pH, numerically relates the hydrogen ions concentration or activity. The pH is approximately equal to the negative logarithm of H+ concentration expressed in molarity. pH 7 is neutral; above it alkalinity increases and below it acidity increases. pH indicators are usually weak acidic or basic organic tautomers which exist in more than one structural form of which at least one form is characteristically colored in relation to different electronic configuration of the bound. Indicators should not change color exactly at one pH value, but within a wide pH range. The transition point of an indicator is defined as the point at which the acid and alkaline forms of the indicator exist in equal concentrations

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