Unhydrogenated and hydrogenated sunflowerseed oils were exposed to the autoxidation process by sunlight under atmospheric conditions. Experiments were carried out in equal-sized glass, PET (polyethylene terephthalate) polymer, and metal (covered by tin) containers. The reaction time was 30 d, and the reaction course was observed by determining weight changes and peroxide values (PV) of the oil samples at the same time within 2-d intervals. The logarithm of the PV was plotted against time, and straight lines were obtained from the 4th or 6th d. The autoxidation reaction constants were obtained for each oil in each container. When comparing the reaction constants, the unhydrogenated oils autoxidize easily, and the autoxidation reaction occurs faster in sunlight in glass than in the PET polymer container and much faster than in the darkness of the metal container.

The bleaching process for sunflowerseed oil follows a rate formula, log (A/A 0 ) = −k √ √ t , according to absorbance measurements. The dark color of crude oil converts to a light color as the absorbance value decreases. The activation energy E a was calculated from the Arrhenius equation as 3 kJ, and other activation thermodynamic parameters were determined as ∆S ≠ = −4.4 J K −1 , ∆H ≠ = −31.2 J mol −1 , and ∆G ≠ = 1.6 kJ mol −1 . The study showed that the bleaching process was exothermic, presented a decrease of entropy, and was a nonspontaneous process during activation. JAOCS 75, 531-533 (1998).

pH changes as a function of concentration for sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) were observed by addition of 1 N HCl and 1 N KOH. pH values increased up to the critical micellar concentration (CMC) for the SDS/HCl system and decreased for the CTAB/KOH system. In the SDS/HCl and CTAB/KOH systems, the micellar phase had a fixed composition and was homogeneous and monodisperse above the CMC. However, in the SDS/KOH and CTAB/HCl systems, pH values increased continuously and gradually below and above the CMC, and the properties of the micellar phase changed as a function of concentration, giving rise to inhomogeneity and polydispersity. JSD 1, 49-51 (1998).KEY WORDS: Cetyltrimethylammonium bromide, critical micellar concentration, hydrochloric acid, micelle formation, pH, phase separation, potassium hydroxide, sodium dodecyl sulfate.Some early investigators observed fairly abrupt changes in a number of physicochemical properties at or near the critical micellar concentration (CMC) and concluded that micelle formation had at least some of the properties of a phase change. A phase-separation or two-phase model was often used to describe the thermodynamics of micelle formation (1-3). The two-phase model predicts a homogeneous monodisperse micellar phase and a constant monomer concentration above the CMC (4). Careful experimental measurements using highly purified systems revealed that somewhat gradual and continuous changes in physicochemical properties occurred near the CMC (5-8), that micelles appeared to be polydisperse (9), and that monomer activities changed above the CMC (5,10).For example, gradual and continuous decreases in the equivalent conductance of sodium dodecyl sulfate (SDS) in water (7,11) and changes in the heats of micelle formation for alkyl carboxylates (8,12) in water have been observed. In addition, a significant decrease in surface tension was observed for SDS in water above the CMC, indicative of a change in monomer activity (5).The purpose of this investigation is to propose an explanation for micelle formation and phase separation of SDS/HCl, SDS/KOH, CTAB (cetyltrimethylammonium bromide)HCl and CTAB/KOH systems by measuring pH as a function of concentration. EXPERIMENTAL PROCEDURESSDS [CH 3 (CH 2 ) 11 OSO 3 Na], CTAB [CH 3 (CH 2 ) 15 N + (CH 3 ) 3 ]-Br − , HCl (hydrogen chloride), and KOH (potassium hydroxide) were supplied by Merck (Darmstadt, Germany) and were all of analytical grade. pH values were measured at 25°C with a digital pH meter, Model 3040 (Jenway Ltd., Felsted Dunmow Essex, United Kingdom), pH range −2 to 16.000, resolution 0.001, and accuracy ± 0.005.First, 55 mM SDS and CTAB solutions were prepared, separately, and then each solution was diluted with water from 55 to 10 mM in increments of 5 mM. For the SDS/HCl systems, first, a solution of 29.91 mL of 55 mM SDS and 0.09 mL of 1 N HCl (30 mL total) was subjected to pH measurement, and then diluted with water to 50 mM. The same amount of acid (0.09 mL of 1 N HCl) was added to this diluted sol...

The densities and viscosities of unhydrogenated and hydrogenated sunflowerseed oils have been determined at temperatures ranging from 25 to 50°C at 5°C intervals. The densities of these oils vary linearly with temperature. The values of the parameters for the density equation have been calculated.Smooth curves were obtained when the changes in viscosity with temperature were plotted in the form of In 1] vs. 1/1-. The energy of activation, the free energy of activation, and the entropy of activation have been calculated at 25°C, and they decreased with the degree of unsaturation in the fatty acid chains of the sunflowerseed oil.JAOCS 72, 1519-1522 (1995).

Sodium, calcium, aluminum, and tin stearates behave as weak electrolytes in dilute solutions (60% benzene + 40% methanol, vol/vol) below the critical micelle concentration, and conductance data can be explained on the basis of Ostwald's formula and the Debye-Hückel theory of weak electrolytes. Dissociation constants and thermodynamic parameters for dissociation and micellization of these soaps were also evaluated. Micellization was spontaneous and predominant over the dissociation process. JAOCS 74, 793-796 (1997).Specific and equivalent conductivities of sodium and potassium soaps in alcohols, toluene, and pyridine have been determined by Bhatnagar and Prasad (1). Patrick et al.(2) pointed out that sodium oleate in alcohols behaves as a simple electrolyte. Several workers (3,4) have investigated soap solutions that bridge the transition from aqueous to nonaqueous solutions.Critical micelle concentrations (CMC) of aqueous solutions of magnesium soaps were determined by Varma and Kumar (5). Varma and Dayal (6) studied the conductance behavior of aqueous solutions of barium, strontium, and nickel soaps.Mehrotra and Upadhyaya (7) studied the thermodynamics of dissociation and micellization of praseodymium and neodymium linoleates in mixed organic solvents to determine physicochemical properties and structure.In this work, we focused on conductance and micellar behavior of sodium, calcium, aluminum, and tin (stannic) stearate soaps in a mixture of 60% benzene and 40% methanol (vol/vol) at different temperatures. EXPERIMENTAL PROCEDURESSodium hydroxide (NaOH), calcium sulfate dihydrate (CaSO 4 ·2H 2 O), aluminum sulfate-18-hydrate [Al 2 (SO 4 ) 3 ·18H 2 O], tin (IV) chloride (SnCl 4 ), and stearic acid (C 17 H 35 COOH) were supplied by Merck (Darmstadt, Germany). The melting range of the stearic acid was 68-70°C, and its acid number was 196.Sodium stearate was obtained from the reaction of NaOH with stearic acid. Ca 2+ , Al 3+ , and Sn 4+ stearates were prepared by direct metathesis of Na + stearate with the stoichiometrically required amounts of CaSO 4 ·2H 2 O, Al 2 (SO 4 ) 3 ·18H 2 O, and SnCl 4 in a water-alcohol medium (1:1, vol/vol). The precipitated soaps were washed with water and acetone to remove excess metal ion and unreacted stearic acid.Soap solutions were prepared by dissolving a measured amount of soap in a mixture of 60% benzene and 40% methanol (vol/vol) and were kept for 2 h in a thermostatted water bath at the desired temperature.Conductance of the soap solutions was measured with an Orion digital conductivity meter, Model 126 (Orion Research Inc., Boston, MA), and a dipping-type conductivity cell (cell constant 1.01) with platinized electrodes. The reproducibility of the measurements was ±0.1%. RESULTS AND DISCUSSIONSpecific conductance K of Na + , Ca 2+ , Al 3+ , and Sn 4+ stearate soap solutions in 60% benzene and 40% methanol (vol/vol) increases with increases in soap concentration and temperature. Plots of specific conductance K vs. soap concentration C (Fig. 1) are characterized by the intersec...