Barium octylsulphate

Barium octylsulphate (BaOS) is virtually insoluble in water and does not form any liquid crystalline phase with water between 298 and 323 K. Addition of decanol to the aqueous system leads to the formation of the lamellar liquid crystalline phase, yet incompletely characterized. However, it appears that the lamellar phase exists at low water contents and probably occupies a small area in the phase diagram. The phase diagrams of the barium surfactant systems are compared with those of the corresponding systems with and Ca + counterions and the results are discussed in the light of electrostatic theory. 

Key words Barium di-2-ethylhexylsulphosuccinate, barium octylsulphate, liquid crystals, phase diagram, NMR... 

The studies reported so far on the surfactant systems with divalent counterions are very few and limited to calcium and magnesium. Here we present the binary phase diagram (composition vs temperature) of the system barium di-2-ethylhexyIsulphosucdnate (BaA2)- iO. We will also make a preliminary report on the isothermal ternary system of barium octylsulphate (BaOS)-decanol- /). 

In the ternary alkaline earth octylsulphate-decanol-water system, the extension of the lamellar liquid crystalline phase towards the water comer increases in the order Mg " > Ca + > Ba (28 moles 0 per mole surfactant ion for magnesium against 18 moles for the calcium system and not quantified for the barium system). On the other hand, the minimum amount of water necessary to form the lamellar liquid crystalline phase in the calcium and magnesium systems is approximately the same, 8 moles per mole surfactant ion [4],... 

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