sodium alkyl sulfate
azo oil dye
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract Thermodynamics of surfactant-dye complex formation have been studied, in terms of equilibrium coefficient, using a spectrophotometer. The systems are 6 sodium alkyl sulfates, which have different alkyl chain lengths, and 4-phenylazo-1-naphthylamine. A pronounced spectral change in the dye solution occurs on addition of the surfactant; the change has a definite isosbestic point and a new absorption band at 535 nm because of surfactant-dye complex formation, which is caused by hydrophilic-hydrophilic interaction. As the alkyl chain length in the surfactant increases, the values of free energy change (negative) increase, while the value of enthalpy change (negative) increases and the value of entropy change (positive) decreases. The longer the alkyl chain length in surfactant increase, the more stable the surfactant-dye complex becomes. Surfactant-dye complex will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction.
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