Determination of pK(a)'s for thymol blue in aqueous medium: evidence of dimer formation期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

Determination of pK(a)'s for thymol blue in aqueous medium: evidence of dimer formation

Authors:	Balderas-Hernández P Ramírez M T Rojas-Hernández A Gutiérrez A

Affiliation:	^a Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Apdo. Postal 55-534, C.P. 09340, México D.F., Mexico ^b Facultad de Estudios Superiores Cuautitlán, U.N.A.M, Sección de Química Analítica, Av. Quetzalcóatl s/n Cuautitlán Izcalli, Estado de México, C.P. 54740, Mexico

Abstract:	Formation constants for recrystallized thymol blue were determined in water, using the SQUAD and SUPERQUAD programs. The best model correlating spectrophotometric, potentiometric and conductimetric data was fitted with the dissociation of HL⁻=L²⁻+H⁺−log K=8.918±0.070 and H₃L₂⁻=2L²⁻+3H⁺−log K=29.806±0.133 with the SUPERQUAD program at variable low ionic strength (1.5×10⁻⁴–3.0×10⁻⁴ M); and HL=L²⁻+H⁺−log K=8.9±0.000, H₃L₂⁻ =2L²⁻+3H⁺−log K=30.730±0.032, H₄L₂=2L²⁻+4H⁺−log K=32.106±0.033 with SQUAD at 1.1 M ionic strength.

Keywords:	Aqueous medium Formation constants Recrystallized thymol blue
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