Title: Bromthymol Blue
CAS Registry Number: 76-59-5
CAS Name: 4,4¢-(3H-2,1-Benzoxathiol-3-ylidene)bis[2-bromo-3-methyl-6-(1-methylethyl)phenol] S,S-dioxide
Additional Names: a,a-bis(6-bromo-5-hydroxycarvacryl)-a-hydroxy-o-toluenesulfonic acid g-sultone; 3,3¢-dibromothymolsulfonphthalein
Molecular Formula: C27H28Br2O5S
Molecular Weight: 624.38
Percent Composition: C 51.94%, H 4.52%, Br 25.59%, O 12.81%, S 5.14%
Literature References: Prepd by the action of bromine on thymol blue in glacial acetic acid: Clark, Lubs, J. Wash. Acad. Sci. 5, 609 (1915); 6, 482 (1916); Chem. Zentralbl. 1916, I, 175; II, 1068. See also ref under Bromcresol Green.
Properties: Cream-colored crystals. Sparingly sol in water; sol in alcohol and in aq solns of alkalies. Also sol in ether. Less sol in benzene, toluene, xylene. Practically insol in petr ether. pK = 7.0. To prepare a soln for use as pH indicator, dissolve 0.10 g in 8.0 ml N/50 NaOH and dil with water to 250 ml. To prepare a soln for use as indicator in volumetric work, dissolve 0.1 g in 100 ml of 50% alc.
pKa: pK = 7.0
Use: As indicator, pH 6.0 yellow; pH 7.6 blue.