Abstract
The critical micelle concentration (CMC) and the thermodynamic function of the anionic surfactant, sodium laurate (SLA) and sodium dodecyl sulfate (SDS) in the N,N-dimethyl acetamide (DMA)/long-chain alcohol systems were studied using titration microcalorimetric method. The power-time curves of SLA and SDS in the presence of a long-chain alcohol (n-heptanol, n-octanol, n-nonanol, n-decanol) in the DMA medium were deter-mined. Then, from the curves, the critical micelle concentration (CMC) and the thermodynamic standard formation functions (△Hθm, △Gθm and △Sθm) were obtained through thermodynamic theories. The relation-ships between temperature, alcohol's carbon number, concentration and thermodynamic properties were dis-cussed. For SLA or SDS in a DMA solution, under the same concentration of alcohol, the values of CMC, △Hθmand △Sθm increase, while the values of △Gθm decrease with the increase of temperature. Under the same condition of identical temperature and alcohol concentration, the values of CMC, △Hθm, △Gθm and △Sθm decrease with the increase of the alcohol's carbon number. In the presence of the same kind of alcohol, the values of CMC and △Gθm increase, but the values of △Hθm and △Sθm decrease with the concentra-tion increases in alcohol series at the same temperature.
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