Solutions of alkali soaps and water in fatty axids VII. X-ray scattering of the isotropic liquid L2-phase

Ekwall, Per; Fontell, Krister

doi:10.1007/bf01452817

Cited by 18 publications

(15 citation statements)

References 11 publications

(9 reference statements)

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“…It may be added that a dividing up of the dimers would not influence the molecular length, but only decrease the cross-section of the molecule. This is in accordance with the Xray scattering studies which indicate that, in this concentration region, no decrease in the length of the particles occurs [14,15]. However, the real cause for the decrease in viscosity cannot be found on the basis of the results of our observations presented so far.…”

Section: Introductionsupporting

confidence: 94%

“…The light scattering and the quasi-Bragg values [13][14][15] show a continuous increase; moreover, the value of the reduced viscosity remains quite unaltered up to a water content of about 33 % and increases thereafter very slowly (Fig. 2).…”

Section: Acid Octanoates At Water Contents Between About 25 and 40 0~mentioning

confidence: 90%

“…Therefore we will restrict ourselves to the following experimental observations. The study of X-ray scattering in the small-angle region has shown that the curve for the quasi-Bragg values increases almost linearly up to a water content of 40 % becomes almost horizontal between 40 and 50 0/0, but thereafter increases again [14,15]. The reduced viscosity remains almost unchanged at water contents between 25 and 33 % and thereafter increases very slowly up to a water content of about 50 % but begins to decrease rather rapidly at high water contents (Fig.…”

Section: Acid Octanoates At Water Contents Between About 25 and 40 0~mentioning

confidence: 97%

“…Data from light scattering studies [13] and X-ray findings [14,15] indicate that in series with constant molar ratios between water and sodium octanoate, above the molar ratio 3 between the two amphiphilic components, there is a fixed particle size of the hydrated acid octanoate and that the size is quite close to that in the non-aqueous melt. This view is supported by viscosity studies; in all series, the reduced viscosity gives curves having the same smooth and slow increase as in the non-aqueous melt, up to a content of about 1.1-1.2 moles acid octanoate (Fig.…”

Section: Introductionmentioning

confidence: 93%

“…This basic molecular structure characterizes the non-aqueous acid sodium octanoate in the melt. Measurements of light scattering [13] and studies of X-ray scattering in the small-angle region [14,15] indicate that the size of the particles remains unchanged and differs very little from that of the dimers of the fatty acid. The same conclusion may be obtained from viscosity studies (Fig.…”

Section: Introductionmentioning

confidence: 98%

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Solutions of alkali soaps and water in fatty acids X. The basic structure of the molecules and the size of the particles of acid octanoates in the L2-phase at water contents below 40%

Ekwall¹

1988

Colloid & Polymer Sci

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Abstract:The acid sodium octanoate molecules in the isotropic liquid L2-phase of the system sodium octanoate-octanoic acid-water have the same basic structure in the whole region, from non-aqueous melt up to a water content of 40 %. This molecular structure is characterized by amphiphilic units oriented with the polar groups directed inwards and bound to each other, forming a central core from which the hydrocarbon chains protrude in at least two opposite directions. The size of the molecules increases due to the incorporation of water, and their shape changes from spherical to elongated rods or ribbons. They occur as monomers or dimers; no aggregation to lasting large particles has been observed. However, transient agglomerates of the free molecules seem to occur.

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Section: Introductionsupporting

confidence: 94%

Section: Acid Octanoates At Water Contents Between About 25 and 40 0~mentioning

confidence: 90%

Section: Acid Octanoates At Water Contents Between About 25 and 40 0~mentioning

confidence: 97%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 98%

See 3 more Smart Citations

Solutions of alkali soaps and water in fatty acids X. The basic structure of the molecules and the size of the particles of acid octanoates in the L2-phase at water contents below 40%

Ekwall¹

1988

Colloid & Polymer Sci

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Soap

Zhu

Chambers

Naik

2006

Kirk-Othmer Encyclopedia of Chemical Technology

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2.2. Phase Behavior. Soap as an anionic surfactant in water can form a range of aggregates with different shapes and sizes depending on its concentration and the temperature. Its interaction with water is also influenced by the hydrocarbon chain length, the saturation of the hydrocarbon chain and the counter ions property. Furthermore the presence of other surfactants and electrolytes can also significantly change its phase behavior.Binary Soap-Water System. Mixtures of soap in water exhibit a rich variety of phase structures (4,5). Phase diagrams chart the phase structures, or simply phases, as a function of temperature (on the y-axis) and concentration (on the x-axis). Figure 1 shows a typical soap-water binary phase diagram, in this case for sodium palmitate-water. Sodium palmitate is a fully saturated, 16-carbon chain-length soap. At lower temperatures, soap crystals coexist with

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Solutions of alkali soaps and water in fatty acids XI. Correlation between the acid sodium octanoate in the most water-rich part of the L2-phase and the acid soaps in two adjacent phases

Ekwall¹

1988

Colloid & Polymer Sci

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Abstract:The special nature of the outer-most water-rich region of the La-phase in the ternary system sodium octanoate-octanoic acid-water is evidenced by its somewhat turbid appearance and by the character of its equilibria with adjacent phases. The phase contains aggregated acid sodium octanoate which is dispersed in a very dilute aqueous solution of sodium octanoate. The acid octanoate has the composition I NaCs:2 HC8 :x H20 and is composed of closely packed amphiphilic units, all with the polar groups in the same direction. This acid soap obviously forms double-layered aggregates with the lipophilic hydrocarbon chains pointing inwards and the polar groups pointing outwards towards the surrounding bulk-water. The phase is formed when octanoic acid is added to the L1-phase of the system just above the 1.a.c.; in this aqueous solution, the acid reacts with dissolved acid octanoate 1 NaCs:I HC8:x 1-120 and that results in the formation of the slightly soluble acid soap 1 NaC8:2 HC8 :x H20 that separates as a new phase, the turbid La-phase. On further addition of octanoic acid, the content of the mentioned acid soap increases until the solution phase is transformed into a liquid crystalline lamellar D-phase with the same acid soap composition. This formation of acid soap 1 NaA:2 HA on addition of fatty acid to the dilute soap solution just above the 1.a.c., has been known for a long time to occur in various systems containing a long-chain sodium soap. However, at suitably low temperatures, the reaction in these systems does not result in separation of the acid soap in the liquid crystalline, but in the solid crystalline state.

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Solutions of alkali soaps and water in fatty axids VII. X-ray scattering of the isotropic liquid L2-phase

Abstract: Abstract:The isotropic liquid pase, L2, in the system sodium octanoate/octanoic acid/ water (at 20 ~ exhibits low-angle X-ray scattering. The strength of the phenomenon and the position of the peak in the scattering curve vary with composition. This phenomenon is presented and described.

Cited by 18 publications

References 11 publications

Solutions of alkali soaps and water in fatty acids X. The basic structure of the molecules and the size of the particles of acid octanoates in the L2-phase at water contents below 40%

Solutions of alkali soaps and water in fatty acids X. The basic structure of the molecules and the size of the particles of acid octanoates in the L2-phase at water contents below 40%

Soap

Solutions of alkali soaps and water in fatty acids XI. Correlation between the acid sodium octanoate in the most water-rich part of the L2-phase and the acid soaps in two adjacent phases

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