Studies on the thermal behaviour of mono- and di-imines of some diaminonaphthalenes

The mono- and di-imines of some diaminonaphthalenes were prepared using a solid solid reaction technique. Their structures were studied using elemental analysis, infrared and electronic spectra. The thermal behaviour of the obtained compounds and their solid solid preparation reactions have also been studied. The energies of activation as well as the reaction orders of those reactions were determined.     

Studies on the aggregation behaviour of some direct dyes in aqueous solutions

Summary Physicochemical properties of the two direct dyes ChrysophenineG and Chlorazol Sky Blue FF in aqueous solutions, have been studied using solubility and electrical conductivity methods. The results indicate that in aqueous solutions, both dyes in the presence of added sodium chloride start forming aggregates at a critical dye concentration. This critical concentration is a function of the temperature and the concentration of added sodium chloride. An analysis of the conductivity data shows that in all solutions containing dye aggregates the concentration of single dye ions is constant and equal to the critical cocentration. Since the solubility of ChrysophenineG unlike that of Chlorazol Sky Blue FF, is very small in the presence of added sodium chloride, the solubility product principle has been used to experimentally determine mean ionic activity coefficients for the dye ions. These values have been compared with activity coefficients calculated using a suitable form of theDebye-Hückel expression. The results indicate that ChrysophenineG in aqueous solutions behaves as a strong unaggregated 12 valence type electrolyte in dilute solutions below the critical concentration for aggregate formation.Finally, a close correlation has been shown to exist between the critical dye concentrations for aggregate formation and the equilibrium dye bath concentrations at which the aqueous solution adsorption isotherms for these dyes on cotton, viscose and cuprammonium rayon fibres show a marked change in slope leading to the formation of a flat plateau region.     

Studies on the electrocapillary curves of anionic surfactants in presence of non-ionic surfactants

Polyoxyethylated non-ionic surfactants such as Tween 20, Tween 40, Nonidet P40 and Nonex 501 have been supposed to be associated with cationic characteristics. Studies on the effect of these surfactants on the electrocapillary curves of the anionic surfactants Aerosol IB, Manaxol OT and sodium lauryl sulphate (SLS), show that the electrocapillary maxima shift towards positive potentials. The order of adsorption of the anionic surfactants is SLS > Manaxol OT > Aerosol IB while the shift in maxima is in the order Aerosol IB ~ Manaxol OT > SLS which confirms association of cationic characteristics with the micelles of these non-ionic surfactants. The magnitude of the shift in electrocapillary maxima is Nonex 501 > Nonidet P40 > Tween 20 > Tween 40 which may be the order of magnitude of the positive charge carried by these non-ionic surfactants.     

Studies on the retention behaviour of some thiazolylazo derivatives in reversed phase liquid chromatography

The retention behaviour of thiazolylazo derivatives, 4-(2-thiazolylazo) resorcinol (TAR), 4-(2-thiazolylazo)-orcinol (TAO), 2-(2-thiazolylazo)-4-methylphenol (TAC) and 1-(2-thiazolylazo)-2-naphtol (TAN) was studied by reversed phase liquid chromatography. The optimum conditions for the separation of four thiazolylazo derivatives were examined with respect to column, flow rate, mobile phase composition and pH of mobile phase. These derivatives were separated simultaneously on Symmetry C₈ column using composition of acetonitrile/water (60/40, v/v) as mobile phase. The capacity factor (k′) has been decreased at higher pH than pK_a of solute which may due to the increasing concentration of the ionized species as increase the pH of mobile phase. The dependence of log k′ on the volume faction of water in the binary mobile phase and k′ on the liquid–liquid extraction distribution ratio (D_c) in acetonitrile–water (60/40, v/v)/n-octane extraction system for thiazolylazo derivatives were obtained good linear relationship. The results showed that the retention behaviour of these derivatives was mainly affected by the hydrophobic interaction between thiazolylazo as solute and mobile phase.     

Studies on the molecular interaction of safranin-T with surfactants

The spectrophotometric studies of safranin-T (Saf-T) dye in an aqueous solution containing three different types of surfactants such as CTAB (cationic), SLS (anionic) and Triton X-100 (TX-100), Tween-20, 40, 60 and 80 (nonionic) show that Saf-T forms a 1:1 molecular complex with TX-100, Tweens and SLS. Such a type of interaction is absent in Saf-T and CTAB. The thermodynamic and spectrophotometric properties of these complexes suggest that Saf-T forms a strong charge transfer (CT) complex with TX-100 and Tweens, whereas the interaction of Saf-T with SLS is coulombic in nature. Photogalvanic and photoconductometric studies also support the above interactions. In addition to this, the electron-donating ability among the nonionic surfactants i.e. TX-100 and Tweens towards dye, role of surface in CT interaction, the site of CT interaction and the intensity and stability of CT interaction between Saf-T and nonionic surfactants have been pointed out.     

Silicon-modified carbohydrate surfactants. IV. The impact of substructures on the wetting behaviour of siloxanyl-modified carbohydrate surfactants on low-energy surfaces

The siloxanyl-modified carbohydrate surfactants investigated consist of the four structural elements: (1) siloxanyl moiety; (2) spacer; (3) carbohydrate unit; and (4) modifying element. By static surface tension (γ_sν — γ_sβ α) measurements the contact angles of the aqueous surfactant solutions above the critical micelle formation concentration (cmc) on nonpolar perfluorinated surfaces (FEP^® plate) were determined. Although the siloxanyl units were found to have a high capacity to level out the interfacial properties, both surface tension and wetting tension react independently to defined changes in the chemical structure of the surfactant molecules. The results of spreading experiments on polyproylene show good correlation with the dependences found by wetting meaurements. © 1997 John Wiley & Sons, Ltd.     

Studies on the polarographic behaviour of estazolam

In 0.1M NH(3)-NH(4)Cl buffer (pH 9.2) a sensitive 2-electron reduction wave of estazolam is obtained by single-sweep oscillopolarography. The peak potential is -1.08 V (vs. SCE). The peak height is proportional to the concentration of estazolam over the range 1.0 x 10(-7)-9.0 x 10( partial differential)M. The detection limit is 5.0 x 10(-8)M. The behaviour of the reduction wave has been studied and applied to the determination of estazolam. The reduction process is irreversible and the wave shows adsorptive characteristics, the behaviour obeying the Frumkin adsorption isotherm. The adsorption coefficient beta is 1.16 x 10(6) 1./mole and the interaction factor alpha is -1.06. The mechanism of the electrode reaction is discussed.     

The influence of surfactants on the behaviour of heavy metals in the system n-octanol-water

The partition of heavy metals between octanol and water in the presence of surfactants has been investigated. It is shown that metal ions can be extracted from water into the organic phase, n-octanol, as a model for biological materials in the presence of various anionic surfactants. Anions such as chromate can be extracted with the help of certain cationic surfactants. It was found that the extent of extraction depends on various parameters, such as the concentration of the surfactant, ionic strength and pH. With some anionic surfactants, the K_(ow) of lead or cadmium can reach values of 200 from waters of low ionic strength, decreasing as the ionic strength increases.     

Adsorption kinetics measurements of some nonionic surfactants

Dynamic surface tension values of aqueous surfactant solutions were measured by using the ring and plate method. The mean diffusion coefficients calculated on the basis of the purely diffusion controlled adsorption model vary between 2 · 10^–6 to 7 · 10^–6 cm²/s for all surfactants studied:n-alkanols,n-alkanoic acids, dimethyl and diethyln-alkyl phosphine oxides. That means the surfactants investigated adsorb with a purely diffusion controlled adsorption mechanism and no barriers excist to hinder sorption processes.Nomenclature c ₀ surfactant bulk concentration - D diffusion coefficient - surface concentration - ₀ equilibrium surface concentration - ¯ (t)/ ₀ reduced surface concentration - maximum surface concentration - K ₀/c₀ - surface tension - t time - Dt/K ² reduced time - a _L coefficient of the Langmuir isotherm     

Influence of nonionic surfactants on the chromatographic behaviour of proteins in hydrophobic interaction chromatography

The chromatographic characteristics of proteins in the presence of additives of nonionic surfactants Brij-35 and Tween-80 in the conditions of descending gradient of ammonium sulfate and phenyl-coated polymeric stationary phase were investigated. It was revealed that retention factors of proteins may be regulated by use of mentioned additives. The improvement of resolution is achieved for some hardly separated pairs of proteins, viz. albumin egg/albumin bovine, aldolase/tripsin. A reversion of the elution order is observed for tripsin/chymotrypsinogen A.     

Effect of some anionic surfactants on the stability of oxytetracycline hydrochloride stabilized emulsion

Summary The zeta potential of oxytetracycline hydrochloride stabilized emulsion flocculated by the addition of anionic surfactants has been calculated. The interaction energies of these emulsions have also been evaluated and the stability discussed in the light of D. L. V. O. Theory. The energy barriers, thus obtained, were very high, which prevented the occurrence of flocculation in primary minima. The flocculation could, however, occur in the secondary minima. The flocculation studies were carried out haemocytometrically and the degree of aggregation (D) calculated. In order to account for the observed values ofD, the effective Van der Waals constant of the system should be 2.3 x 10^-13 erg. The binding parameters and free energy of adsorption have also been calculated.

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Zusammenfassung In der Arbeitr wird über die Berechnung des Zetapotentials von Emulsionen berichtet, die mit Oxytetracyclinhydrochlorid stabilisiert und durch Zusatz von anionischen Tensiden geflockt wurden. Auch die Wechselwirkungsenergien werden abgeschätzt und die Stabilität im Licht der DLVO-Theorie diskutiert. Die so erhaltenen Energiebarrieren sind sehr hoch und verhindern eine Flockung im primären Minimum. Die Flockung könnte jedoch im sekundären Minimum erfolgen. Die Untersuchungen wurden durch Flockungsstudien ergänzt, ebenso durch Berechnung von Bindungsparametern und der freien Energie der Adsorption.

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With 6 figures and 4 tables     

Aqueous behaviour of cationic surfactants containing a cleavable group

The aggregation behaviour of two novel cationic RAFT agents (transfer surfactants); N,N-dimethyl-N-(4-(((phenylcarbonothioyl)thio)methyl)benzyl)ethanammonium bromide (PCDBAB) and N-(4-((((dodecylthio)-carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium bromide (DCTBAB) in diluted solutions have been investigated by surface tension, conductimetry and microcalorimetry measurements. The thermodynamic parameters i.e. the critical micelle concentration (cmc), the degree of micelle ionization (alpha), the head group surface area (a 0), Delta H mic, Delta G mic and T Delta S mic are reported at 303 K. The thermodynamic parameters have been compared to those of the conventional surfactant cetyltrimethylammonium bromide (CTAB) in order to specify structural relationships. The obtained results have been discussed considering the hydrophobic behaviour of the S-C=S- linkage and the specific interactions that arise from the introduction of the benzene ring into the hydrophobic part.     

Studies on the ion-exchange behaviour of chromium ferrocyanide

The sorption of univalent, bivalent and trivalent ions has been studied on chromium ferrocyanide gel. The studies reveal a high sorption capacity for Cs⁺, Tl⁺, Ag⁺, Cu²⁺, Zn²⁺, Cd²⁺, Fe³⁺ and Th⁴⁺. The sorption of monovalent cations show purely ion-exchange mechanism while the uptake of bivalent and trivalent cations is non-equivalent in nature. Single elution of Rb⁺, Cs⁺ and Tl⁺ has been performed from the columns of this exchanger and the recovery is almost complete in all the cases. Cu²⁺ and Ag⁺ get completely adsorbed on the gel column and their elution is not possible probably due to the formation of some new solid phases. Depending on the K_d values of the metal ions, a large number of separations of radiochemical as well as analytical importance can be performed on the columns of this exchanger material.     

Studies of the aggregation behavior of cyclic gemini surfactants

The specific conductance, surface tension, mean aggregation number, and apparent molar volume properties of aqueous solutions of a novel series of N,N'-bis(cyclododecyldimethyl)-alpha,omega-alkanediammonium dibromide (c12-s-c12) surfactants, where s is the spacer chain length, are reported. Surfactants with s = 3, 4, and 6 have been prepared and characterized in terms of their Krafft temperature (T(Kr)), critical micelle concentration (cmc), surfactant head group area (a) at the air-water interface, mean aggregation number (N(agg)), and the volume change upon micelle formation (deltaV(phi,M)). The c12-3-c12 shows little evidence of aggregate formation, while the results obtained for the c12-4-c12 and c12-6-c12 homologues suggest the formation of small, poorly defined micellar aggregates in aqueous solution.     

Thermal behaviour of some minerals

Thermal behaviour of some minerals (kaolinite, halloysite, two montmorillonites, quartz and calcite) for different sample amounts and heating rates has been investigated using differential thermal analysis. On the basis of the DTA analysis carried out, the PA curves of each mineral have been obtained for different heating rates. These diagrams can be employed in the semiquantitative evaluation of identical substances contained in uncharacterized polymineral samples.     

Polarographic behaviour of some o-hydroxyketoximes

The polarographic behaviour of three o-hydroxyketoximes, CH(3)C(6)H(3)(OH)CRNOH, where R CH(3), C(2)H(5) and C(3)H(7), has been studied in 5% ethanolic medium, with potassium chloride as supporting electrolyte. A single four-electron reduction wave is obtained which diminishes with increase in pH, being replaced by a new wave in alkaline media. A trough is formed on the limiting-current plateau at higher negative potentials. A mechanism has been proposed for the reduction at the dropping mercury electrode.