Products / pH Indicators


C.A.S. No. 1945-77-3
M.F. C37H40N2Na4O13S
M.W. 844.76gm/mole


Solubility 0.1 % (Dist. water) Clear solution
Absorption maximum (Dist. water) ?max 437-443nm
Absorptivity maximum (A1%/1cm, in water, at ?max) >120
Loss On Drying (110°C) <10%
Suitability as indicator for Metal Titration Passes test

Chemical Name

3,3-Bis(N,N-Di(Carboxymethyl)Aminomethyl)Thymolsulfonephthalein, Sodium Salt

InChI Key



Water soluble (10 g/l, H2O, 25 °C). Soluble in Methanol

Product Description:

Methylthymol blue is a Water soluble chelometric indicator.Methylthymol blue (MTB) is a metal- lochromic indicator which forms metal complexes different in spectral absorption characteristics from the free indicator. The barium complex is formed at relatively high pH with maximum absorption at 608 nm; free MTB at the same pH has a maximum absorption at 460nm.


Methylthymol Blue sodium salt is used as thymol-containing organic dye for complexometric titration for Strontium. Methylthymol Blue sodium salt is mainly used for determining the calcium content in biological samples. It is used in determination of sulfate in rainwater. It combines with silica gel and aids in the separation and preconcentration of trace amounts of heavy metals from some salts. It is used in automated method applicable for qualitative analysis of presence of alkali metals to groundwater, drinking and surface waters, and domestic and industrial wastes.

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