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Summary: Transport Properties for Aqueous Solution
of Sodium Sulfonate Surfactants
1. Mutual Diffusion Measurements: Evaluation of the Equilibrium Parameters
for the Micellization Process
Onofrio Annunziata, Lucia Costantino, Gerardino D'Errico, Luigi Paduano, and Vincenzo Vitagliano
Dipartimento di Chimica, Universita` di Napoli, Federico II, Via Mezzocannone 4, 80134 Naples, Italy
E-mail: vita@chemna.dichi.unina.it
Received July 24, 1998; accepted April 14, 1999
Isothermal mutual diffusion coefficients (D) have been mea-
sured for binary aqueous solutions of sodium alkylsulfonates at
25°C. The diffusion coefficient values drop as the concentration of
micelles in the system increases. As the length of the hydrocarbon
chain increases, the observed drop in D becomes increasingly
sharp and shifts to lower concentrations. When the micellization
process is treated as a chemical equilibrium, diffusion coefficients
lead to the calculation of the thermodynamic parameters associ-
ation number, n, and the equilibrium constant, K. These param-
eters are briefly discussed in connection with the alkyl chain length
of the surfactants. © 1999 Academic Press
Key Words: diffusion; micelle(s); sodium alkyl sulfonates.
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