The critical micelle concentration (CMC) and thermodynamic function of anionic surfactant sodium laurate (SLA) and sodium dodecyl sulfate (SDS) in the N,N-dimethylacetamide (DMA)/long-chain alcohol systems were studied using titration microcalorimetric method. The power-time curves of SLA and SDS with the presence of long-chain alcohol (n-heptanol, n-octanol, n-nonanol and n-decanol) in DMA system were determined. Then, from the curves, the CMC and thermodynamic functions (ΔH_m⁰, ΔG_m⁰ and ΔS_m⁰) were obtained by thermodynamic theory. The relationships between temperature, alcohol’s carbon number, concentration and thermodynamic properties were discussed. For SLA or SDS in DMA solution, under the same concentration of alcohol, the values of CMC, ΔH_m⁰ and ΔS_m⁰ increase, while the values of ΔG_m⁰ decrease with the increment of the temperature. Under the same condition of identical temperature and alcohol’s concentration, the values of CMC, ΔH_m⁰,ΔG_m⁰ and ΔS_m⁰ decrease with the increment of the alcohol’s carbon number. In the presence of the same kind of alcohol, the values of CMC and ΔG_m⁰ increase, but the values of ΔH_m⁰ and ΔS_m⁰ decrease with the concentration increasing in alcohol series at the same temperature.

Key words: microcalorimetric method, N,N-dimethylacetamide, sodium laurate, sodium dodecyl sulfate, long-chain alcohol, CMC, thermodynamic function