The Effects of Organic Additives on the Solubilities and CMC’s of Potassium Alkyl Sulfates in Water. I. The Effects of Several Hydroxy Compounds

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Abstract
The solubilities and critical micelle concentrations (CMC) of potassium dodecyl sulfate (KDS) and hexadecyl sulfate (KHS) were measured in methanol-, ethanol-, 1-propanol-, ethylene glycol-, 1,2-propanediol-, and glycerol-water mixed solvents over the temperature range from 0 to 40°C. It was found that the higher the hydroxy group density in the solvent, the less the effects on both the solubility and the CMC, and that the presence of an alkyl group in the solvent causes a greater temperature-dependence in the solubility. The solvent effects on the CMC and on the single-ion dispersion were discussed separately. An effect of a net-work structure formed between the hydroxy compound and water on the solubility is suggested. Solvent effects on the alkyl group and the ionic group of a surfactant molecule were separated by considering the difference between the standard free-energy change for the solution process of KHS and that of KDS. The effects on the Krafft point were also discussed in term of the above suggestions.
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