Screening and specification of colour changes of nitritometric indicators

The specification of colour changes of nitritometric indicators, viz., cresyl fast violet acetate, amethyst violet, safranine O, neutral red, methylene violet, neutral violet, phenosafranine, brilliant cresyl blue and lissamine blue BF, in the titration of sulphanilamide has been carried out with the help of tristimulus colorimetry. Apart from the determination of true colour co-ordinates and complementary colour co-ordinates, the quantitative parameters specific colour discrimination (SCD), total colour difference (E*) values of CIE La^*b^*, CIE Lu^*v^* and LAB HNU colour spaces together with the standard deviation of colour matching (S) were also evaluated for all the indicators at different concentrations ratios of nitrite and sulphanilamide, for a quantitative measure of quality of colour change. The quality of colour change of many of the studied indicators is further improved by screening with appropriate inert colorants to obtain a colour transition between complementary colours through colourlessness at the equivalence point.     

Thermal Studies of Cobalt(II), Nickel(II) and Copper(II) Complexes of 4-(Sulfonylazido Phenylazo) Pyrazolones

The thermal decompositions of cobalt(II), nickel(II) and copper(II) complexes of4-(3'-sulfonylazido-6'-methoxyphenylazo)-1-phenyl-3-methyl-2-pyrazolin-5-one H(D¹–SO₂N₃) and 4-(4'-sulfonylazido phenylazo)-3-phenyl-3-methyl-2-pyrazolin-5-one H(D²–SO₂N₃) were studied by thermogravimetry. The decomposition in all cases takes place along two stages. The first stage is due to the elimination of water and nitrogen molecules with the formation of tetracoordinate complexes containing nitrene reactive species[M(DSO₂N:)₂]. The second stage represents the decomposition of the material to the metal oxide. The kinetics of the decomposition were examined by using Coats–Redfern, the decomposition in all complexes was found to be first order for the first and second stages. The activation energies and other activation parameters (H^* and S^* and G^*) were computed and related to the bonding and stereochemistry of the complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal Behaviour of Metal Complexes of 6-(2-Pyridylazo)-3-acetamidophenol

The present work aims chiefly to study the thermal behaviour of complex compounds with general formula: [M(HL)xH₂O](A)yH₂O (where HL=C₁₃H₁₁N₄O₂=6-(2-pyridylazo)-3-acetamidophenol (PAAP), M=Cu(II), Zn(II), Cd(II) and Fe(III) x=1, 3; y=2, 5) while A=CH₃COO^– (Ac), Cl₂. The second formula is [M(H₂L)xH₂O]Cl₂yH₂O, (where H ₂ L=C₁₃H₁₂N₄O₂ (PAAP), M=Ni(II), Co(II) x=3; y=4, 6). The compounds were identified by elemental analysis, FT-IR spectra and TG/DTG,DTA methods. It was found that during the thermal decomposition of complex compounds water molecules of crystallization are released in the first step. In the next step the pyrolysis of organic ligand takes place. Metal oxide remained as a solid product of the thermal decomposition. Mass spectroscopy has been used for the determination of the thermal decomposition on the intermediate products. It was found that the thermal stability of the studied compounds increases as the ionic radii decreases. The activation energy E, the entropy change S ^*, the enthalpy H ^* change and Gibbs free energy change G ^* were calculated from TG curve.This revised version was published online in November 2005 with corrections to the Cover Date.     

The solubility and isotopic fractionation of gases in dilute aqueous solution. IIa. solubilities of the noble gases

A method for the analysis of precise gas solubility data is presented and applied to new determinations of the Henry constant, k₂, for He, Ne, Ar, Kr, and Xe. The values of k₂ are fitted to the same sets of temperature functions which we have tried for oxygen. Our previously proposed power series in 1/T, ln(k_2/P )=a₀+a₁/T+a₂/T² (Mark I), gives the best 3-term fit within the temperature range 0–60°C. For use over the full range to the critical temperature of water, we have discovered a new function given by (T^*)²ln(k_2/P )=A₀(T^*)²+A₁(1-T^*)^1/3+A₂(1-T^*)^2/3(Mark II), where T^*T/T _c1 . It fits our data from 0–60°C nearly as well as Mark I; it fits high temperature data from other sources; and at the critical temperature of water it satisfies theoretical requirements. Expansion of Mark II reveals the relationship between Mark II and Mark I and leads to a 4-term smoothing function, ln(k_2/P )=a_–2(T^*)^–2+a_–1(T^*)^–1+a₀+a₁T^* (Mark III), which we believe gives the best values only for the 0–60°C range. Mark III is used to calculate values for , and , 0–60°C, and a procedure is empolyed to estimate the errors. Agreement is excellent between these results and those obtained from precise microcalorimetric measurements made by others. With the inclusion of pressure correction terms, Mark II yields the four thermodynamic function changes for use at high temperatures. With increasing temperature, these changes suddenly turn upward toward plus infinity as T _c1 is approached. Essentially direct determinations of for argon by other workers are in excellent agreement with our results. The symmetrical activity coefficient at infinite dilution, ₂ ^° is examined and the hypothetical properties of k₂ are explored below 0°C. Mark II can be expressed in the reduced form (T^*)²ln(k ₂ ^* )=A₁(1-T^*)^1/3+A₂(1-T^*)^2/3, where k ₂ ^* k ₂/(p _c12c1). A₂ is a very good linear fit to A₁, which suggests a characteristic temperature for water at 287.3 K.     

Single crystals of regio-selectively substituted cellulose hetero-esters

Lamellar single crystals of some regio-selectively substituted cellulose hetero-esters: cellulose propionate diacetate (CPDA, 2,3-di-O-acetyl-6-O-propionyl cellulose), cellulose acetate dipropionate (CADP, 6-O-acetyl-2,3-di-O-propionyl cellulose), cellulose butyrate diacetate (CBDA, 2,3-di-O-acetyl-6-O-butyryl cellulose) and cellulose acetate dibutyrate (CADB, 6-O-acetyl-2,3-di-O-butyryl cellulose), have been prepared at high temperature in a mixture of dibenzyl ether andn-tetradecane. The CPDA crystals were lozenge-shaped whereas those of CADP, CBDA and CADB had a ribbon morphology. CPDA crystals gave well-resolved electron diffractograms from which the reciprocal lattice parameters a^*=0.807 nm^–1,b ^*=0.400 nm^–1 and ^*=90° could be determined. Systematic absences occurred at every odd reflection along the two orthogonal axesa ^*andb ^*. Thus, the CPDA diffraction pattern is consistent with a p_gg symmetry. For CADP, the electron diffraction pattern is consistent with a p_mg two-dimensional space group withb the unique axis along the ribbon direction. The diagram yields the reciprocal lattice parameters a^* = 0.902 nm^–1,b ^*=0.651 nm^–1 and ^*=90°. The CBDA electron diffractogram yields the following cell parameters and two-dimensional space group:a ^*=0.482 nm^–1,b ^*=0.659 nm^–1 and ^*=90°, and a p_gg symmetry; and that of CADB:a ^*=0.834 nm^–1,b ^*=0.645 nm^–1 and ^*=90°, and a p_mg symmetry.     

The unusual morphological structure of the aging products of coprecipitated Fe(III)-Al(III) hydroxides

Aluminum-substituted hematite ( ^*-Fe₂O₃) with an unusual morphological structure is formed upon the aging of coprecipitated Fe(III)-Al(III) hydroxides with excess Fe(III). The crystals of this hematite are found in separate layers and includes seams of an aluminum-containing phase. In samples with excess Al(III) content, the ^*-Fe₂O₃ crystals are found as seams in mixed aggregates of boehmite and ^*-Fe₂O₃.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 931–933, April, 1990.     

Kinetics and mechanisms of oxidation of 1-octene and heptanal by crown ether-solubilized potassium permanganate in non-aqueous solvents

The kinetics of oxidation of 1-octene and heptanal by 18-crown-6-ether-solubilized KMnO₄ in benzene and CH₂Cl₂ have been investigated. In benzene, the oxidation of 1-octene is first order with respect to the oxidant and zero order with respect to the substrate, whereas in CH₂Cl₂ the reaction is first order with respect to both substrate and oxidant. The reaction of heptanal followed different kinetics being first order with respect to both substrate and oxidant, regardless of whether benzene or CH₂Cl₂ was employed as the solvent. The values of activation energy E _a, standard enthalpy H ^*, standard entropy change S ^*, and standard free energy G ^*, for the reaction, are reported. Mechanistic pathways for the studied reactions are also proposed.     

Study of The Thermal Decomposition of Some New Cyanine Dispersed Dyes

The structure of the studied compounds was confirmed by elemental analysis, IR and NMR. TG and DTG data were used to study the kinetics of the thermal decomposition process of some new cyanine dispersed dyes derived from 2-[(p-chloro)-styryl]-6-[5-(3-aryl-rhodanine)]-1,2-dihydropyridine. The reaction was found to follow first order mechanism. The activation energy E_a was calculated and used to calculate the thermodynamic parameters enthalpy change (H^*), entropy change (S^*), and free energy change (G^*), related to the thermal decomposition process. Two different calculation methods including Coats—Redfern and Chatterjee were applied to evaluate thekinetic and thermodynamic parameters. Quantum study was performed to support both the structure and the thermal data.This revised version was published online in November 2005 with corrections to the Cover Date.     

Stereocontrol in the cationic polymerization of N-vinylcarbazole

The dependence of the steric microstructure of cationically polymerized poly(N-vinylcarbazole) (PVK) upon catalyst, polymerization temperature, and polymerization solvent has been investigated. The effect of polymerization temperature variation was found to be small, whereas the choice of catalyst and polymerization solvent was found to have a strong influence upon the PVK steric microstructure. A correlation was found between the syndiotacticities X_s and the π^* solvent polarities of the polymerization solvents for a given catalyst. A decrease in X_s with increasing π^* solvent polarity was observed using BF₃OEt₂ and AlEt₂Cl catalysts and has been interpreted in terms of propagation via contact ion-pair ring structures reversibly formed between the active end group and a preceding repeating unit. The increase in X_s with increasing π^* solvent polarity observed with several of the catalysts investigated has been interpreted in terms of chain ion pairs whose separation increases with increasing π^* solvent polarity. The influence of the various Lewis acid catalysts upon the steric microstructures of cationically polymerized PVK allowed the following order of nucleophilicity to be established:      

Transfer Reactions of Rydberg (Quasi-Rydberg Molecular) Electrons in Condensed Media: IV. Large Proton Displacements upon Phosphorescence Quenching via Highly Excited Triplet States T* of Substituted Aromatic Solute Molecules in Solutions at 77 K

Intramolecular phosphorescence quenching via states T* in aromatic solute molecules containing N–H (diphenylamine (DPA) or carbazole), O–H (naphthol), etc. bonds was observed in methylcyclohexane at 77 K. The quantum yield of quenching measured for DPA increases with increasing the energy of the T* state. As in the case of external electron acceptors, the quenching and photodissociation are associated with the capture of excited * electrons onto polarized bonds N–H⁺, O–H⁺and with the formation of triplet complexes (for example, Ph₂N···H*, where H* is the excited hydrogen atom). The complexes can be deactivated via configurations with large proton displacement distances (Ph₂N^–···H⁺).     

Kinetics of the solvolysis oftrans-dichlorotetra-(4-t-butylpyridine)-cobalt(III) ions in water +t-butyl alcohol mixtures

Rates of solvolysis of the complex cation [Co(4tBupy)₄Cl₂]⁺ have been determined in mixtures of water with the hydrophobic solvent, t-butyl alcohol. The solvent composition at which the extremum is found in the variation of the enthalpy H^* and the entropy S^* of activation correlates well with the extremum in the variation of the relative partial molar volume of t-butyl alcohol in the mixture and the straight line found for the variation of H^* with S^* is coincident with the same plot for water + 2-propanol mixtures. A free energy cycle is applied to the process initial state (C ⁿ⁺) going to the transition state [M⁽ⁿ⁺¹⁾⁺...Cl^–] in water and in the mixture using free energies of transfer of the individual ionic species, G _t ^o (i), from water into the mixture. Values for G _t ^o (i) are derived from the solvent sorting method and from the TATB/TPTB method: using data from either method, changes in solvent structure on going from water into the mixture are found to stabilize the cation in the transition state, M⁽ⁿ⁺¹⁾⁺, more than in the initial state, C ⁿ⁺. This is compared with the application of the free energy cycle to the solvolysis of complexes [Co(Rpy)₄Cl₂]⁺ and [Coen₂LCl]⁺ in mixtures of water with methanol, 2-propanol or t-butyl alcohol: the above conclusion regarding the relative stabilization of the cations holds for all these complexes in their solvolyses in water+alcohol mixtures using values of G _t ^o (Cl^–) from either source.     

Spectrophotometric determination of lanthanides using 4-(2-Pyridylazo) resorcinol

Summary The formation of red colour produced by the interaction of 4-(2-pyridylazo) resorcinol (PAR) and rare earths has been studied to determine the composition, stability and other characteristics of the chelates formed. The _max of all the chelates was found to be 515 nm atph 6.2 whereas the _max of the PAR reagent at this p_H is 410 nm. The composition of the chelates was found to be 12 (metalPAR) and has been established by two different methods. The stability constant values have been calculated by three different methods. The values of logK, lies in the range of 9.2–10.4 for different rare earth chelates. The chelates are stable over a wide range of p_H. A tentative suggestion has also been made for the position of the chelate ring.

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Zusammenfassung Die rote Farbreaktion von 4-(2-Pyridylazo)-resorcin (PAR) mit Seltenen Erden wurde untersucht, um die Zusammensetzung, die Stabilität und andere Merkmale der dabei entstehenden Chelate zu bestimmen. Beiph 6,2 wurde das Absorptionsmaximum aller Chelate bei 515 nm, das Absorptionsmaximum von PAR bei 410 nm gefunden. Die Zusammensetzung entspricht dem Verhältnis Metall: PAR=12; sie wurde nach zwei verschiedenen Methoden ermittelt. Die Komplexkonstante wurde auf drei verschiedenen Wegen bestimmt. logK liegt bei den verschiedenen Seltenen Erdmetall-Chelaten zwischen 9,2 und 10,4. Die Chelate sind in einem weitenph-Bereich beständig. Die Lage des Chelatrings wurde erörtert.

     

Evaluation of the relaxation modules from the response to a constant rate of strain followed by a constant strain

The stress response σ(t) to a constant rate of strain $ \dot \varepsilon $ ε during the period 0 < t ≤ t^* and to the constant strain ε^* $ ( = \dot \varepsilon t*) $ thereafter is considered in terms of the Boltzmann superposition principle. When t ≤ t^*, the data directly give the constant-rate modulus F (t) ≡ σ(t)/ε(t), which can be converted straightforwardly into the relaxation modulus E(t). Results from illustrative calculations show that a reduction in the relaxation rate effects a decrease in [σ(t^*)/ε^*]/E(t^*) and also in the time at which [σ(t)/ε^*]/E(t) becomes essentially unity. To evaluate E(t) at t > t^*, F(t) is first obtained from σ(t) and F(t ? t^*) by using a derived equation similar to that presented by Meissner. Thereafter, F(t) is transformed into E(t). For illustration, E(t) for a rubbery solid is evaluated over some 2.5 decades of time from its response to a strain rate of 0.25 min^?1 for 0.40 min and thereafter to the attained strain of 0.10 for 5.4 min.     

Formation Enthalpy and Entropy of Exciplexes with Variable Extent of Charge Transfer in Solvents of Different Polarity

Temperature dependence was studied for relative quantum yields of emission from some exciplexes of pyrene, 1,12-benzoperylene, and 9-cyanoanthracene with methoxybenzenes or methylnaphthalenes in solvents of different polarity (ranging from toluene to acetonitrile). The enthalpy H _Ex ^*, the entropy S _Ex ^*, and the Gibbs free energy G _Ex ^*of formation of the exciplexes were determined. Depending of the Gibbs free energy of excited-state electron transfer (G _et ^*) and solvent polarity, the values of H _Ex ^*, S _Ex ^*, and G _Ex ^*vary over the ranges from –5 to –40 kJ mol^–1, from +3 to –90 J mol^–1K^–1, and from +3 to –21 kJ mol^–1, respectively. The possibility is discussed that the effect of solvent polarity G _et ^*on the exciplex formation enthalpies can be rationalized in terms of the model of correlated polarization of an exciplex and the medium.     

High-Pressure 17O-NMR. Study of Vanadium (II) in Water: A Second Example of an Associative Interchange Mechanism (Ia) for Solvent Exchange on an Octahedral Divalent Transition-Metal Ion

The water exchange of [V(H₂O)₆]Cl₂ in aqueous solution has been studied as a function of temperature and pressure (up to 250 MPa), by measuring the ¹⁷O-FT-NMR. line-widths of the free water resonance at 8.13 MHz. The kinetic parameters obtained are K = 87±4 s^?1, ΔH^* = +61.8 ± 0.7 kJ mo1^?1 and ΔS^* = ?0.4±1.9 J mol^?1 K^?1. A pressure-independent volume of activation ΔV^* = ?4.1±0.1 cm³ mol^?1 is obtained, suggesting an associative interchange (I^a) mechanism for this early divalent metal ion.     

Proportionality of intrinsic heat of transport to standard entropy of hydration for aqueous ions

Intrinsic ionic heats of transport q _o ^* (ion) and ionic heats of transport Q _o ^* (ion) have been evaluated for 53 aqueous ions at infinite dilution at 25°C using the reduction rule proposed by the authors and the limiting laws of Agar, and of Helfand and Kirkwood without electrophoretic terms. q _o ^* (ion) have been found to correlate linearly with the standard ionic entropies of hydration for the 38 ions investigated. The correlation yields three distinctive proportionality constants indicating that the ions may be divided into three distinctive groups. Although the sign of Q _o ^* (ion) is not definite, all values of q _o ^* (ion) are positive. For 17 ions Q _o ^* (ion) are in good agreement with TS _o ^* (ion). Here, S _o ^* (ion) is the absolute standard ionic entropy of transport which can be obtained from potentiometric measurements on cells. The values of S _o ^* (ion) were determined by Agar, and recently by Lin and coworkers.     

Specific volume of polysulfone as a function of temperature and pressure

The pressure–volume–temperature (PVT) properties of a commercial polysulfone derived from bisphenol A and 4,4′-dichlorodiphenylsulfone are studied experimentally and theoretically in the temperature range 30–370°C and for pressures to 2000 kg/cm². PVT surfaces are determined for an annealed glass, formed under zero pressure, and for the melt. Two glass-transition lines must be distinguished: T(P) which is the intersection of the glass and melt PVT surfaces, and T_g(P), which is obtained by pressurizing the melt isothermally. The application of Ehrenfest-type equations to these transitions are discussed. The Prigogine–Defay ratio r = Δ_kΔC_p/TV(Δα)² at P = 0 is found to be equal to 0.95 (±20%), using ΔC_p data determined on identical samples. The melt data is compared with the Simha–Somcynski hole theory, using the reducing parameters V^* = 0.788 cm³/g, T^* = 12,560°K, P^* = 10,875 bar. The hole fraction appearing in the theory is found to be constant along T(P), but the glass PVT relationship cannot be reproduced by using the Simha–Somcynsky theory together with the assumption that the hole fraction remains constant in the glass. At P = 0 the hole fraction must be allowed to decrease with decreasing temperature, but at a slower rate than in the melt.     

Selective and sensitive extraction spectrophotometric method for the determination of vanadium (V) as a mixed ligand complex withN-phenyl benzohydroxamic acid and 4-(2-pyridylazo)resorcinol in non-aqueous media

A selective, sensitive and direct method for the spectrophotometric determination of vanadium in steels is developed in which vanadium is extracted withN-phenyl benzohydroxamic acid (PBHA) into chloroform from 5M hydrochloric acid medium followed by colour development by addition of 4-(2-pyridylazo)resorcinol (PAR) inN,N-dimethyl formamide (DMF). The vanadium(V)-PBHA-PAR mixed ligand complex shows maximum absorbance at 560 nm with a molar absorptivity 3.6 × 10⁴ l mol^–1 cm^–1 and obeys Beer's law up to 2.0 g/ml of vanadium. The composition of the mixed ligand complex is determined by Job's method of continuous variations which revealed a 1 1 1 ratio for V(V) PBHA PAR. This method can be directly applied for the determination of vanadium in steels, while in the case of titanium base alloys, after separation of titanium matrix it gives good results even at 50–200 g of vanadium per gram level.     

Phase-fixed double-group 3-Γ symbols. IV. Real 3-Γ symbols and coupling coefficients for the group hierarchies T* ⊃ C 3 * and T* ⊃ C 2 *

We present sets of real 3- symbols which correspond to explicitly given irreducible matrix representations for the two double group hierarchies T* C ₃ ^* and T* C ₂ ^* . They fit into the formalism exposed in a previous paper [1] on the general theory of 3- symbols and coupling coefficients and illustrate much of the discussion in a subsequent one [2] treating the particular properties of the double groups.