PHASE-DIAGRAM OF ALPHA-SULFONATED PALMITIC ACID METHYL-ESTER SODIUM SALT-WATER SYSTEM

The phase diagram of the alpha-sulfonated palmitic acid methyl ester s odium salt (SFMe)-water system was studied by measuring the phase tran sition temperatures (T-c) and the X-ray diffraction patterns for each solid phase of SFMe at various water contents. In the developed phase diagram, one anhydrous solid phase and three distinct hydrated solid p hases (SFMe . 2H(2)O, SFMe . 5H(2)O, and SFMe . 10H(2)O) were recogniz ed as well as liquid crystalline phases, a micellar phase, and a monom er phase. From the analysis of the T-c changes due to the water conten ts of each SFMe solid phase according to the Flory-Huggins-Scott equat ion, it was found that these hydrated SFMe solids form eutectic mixtur es with each other. When the dry and wet SFMe solids were left in an a tmosphere with ordinary relative humidity and temperature, the water c ontent of the SFMe solid converged into the water content correspondin g to that of the SFMe . 2H(2)O.