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Precipitation in solutions containing mixtures of synthetic anionic surfactant and soap. I. Effect of sodium octanoate on hardness tolerance of sodium dodecyl sulfate
Author(s) -
Rodriguez Cheryl H.,
Chintanasathien Chanin,
Scamehorn John F.,
Saiwan Chintana,
Chavadej Sumaeth
Publication year - 1998
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-998-0031-5
Subject(s) - chemistry , sodium dodecyl sulfate , pulmonary surfactant , critical micelle concentration , micelle , sodium , inorganic chemistry , precipitation , nuclear chemistry , chromatography , organic chemistry , aqueous solution , biochemistry , physics , meteorology
The effect of sodium octanoate (SO) and pH on the precipitation of sodium dodecyl sulfate (SDS) with calcium (hardness tolerance) in water was investigated. SO can exist as octanoate anion (O − ) or as the protonated nonionic fatty acid (HO) with the HO/O − ratio increasing with decreasing pH. At intermediate pH levels, SO or SO/SDS systems are composed of mixtures of anionic and nonionic surfactants, resulting in enhancement of micelle formation due to nonideal mixed micelle formation. Above the critical micelle concentration (CMC), the highest hardness tolerance at each pH level occurs at a mole ratio of 80∶20 SDS/SO due to synergism in the SDS/SO mixtures. This synergism also results in an increase in hardness tolerance of SDS with decreasing pH above the CMC.