Showing papers in "Transactions of The Faraday Society in 1966"
TL;DR: In this paper, a quantitative theory is presented which describes the kinetics of coagulation of colloidal systems containing more than one dispersed species, using the linear (Debye-Huckel) approximation for low surface potentials.
Abstract: A quantitative theory is presented which describes the kinetics of coagulation of colloidal systems containing more than one dispersed species. A general expression has been derived to describe the potential energy of interaction between dissimilar spherical colloidal particles, using the linear (Debye-Huckel) approximation for low surface potentials. An overall stability ratio has been defined which takes into account the possibility of interactions between like, as well as unlike, particles in the system. The errors introduced by the use of the linear approximation have been assessed in terms of their effects on the stability ratio, and found to be quite small. The theory has been used to describe the behaviour of a hypothetical system under various conditions.
1,734 citations
TL;DR: In this article, the authors measured the viscosities of binary liquid mixtures at different molar concentrations for fourteen binary liquid systems representing different types and degrees of interaction between unlike components.
Abstract: Viscosities at 25°C have been measured at different molar concentrations for fourteen binary liquid systems representing different types and degrees of interaction between unlike components. Excess viscosities tend to become less negative and then increasingly positive as the strength of the interaction between unlike molecules increases and the excess viscosity is approximately proportional to the strength of the interaction. Some expressions describing viscosities of binary liquid mixtures in terms of those of the components and a parameter attributed to interaction between them are examined. The parameter d in the expression ln η=x1 ln η1+x2 ln η2+x1x2d appears to be a useful measure of the strength of the interaction.
561 citations
TL;DR: In this article, a new family of completely general equilibrium equations was developed to represent the temperature dependence of reaction equilibrium constants in terms of the reaction standard thermodynamic function changes at a chosen reference temperature.
Abstract: A new family of completely general equilibrium equations has been developed to represent the temperature dependence of reaction equilibrium constants in terms of the reaction standard thermodynamic function changes at a chosen reference temperature. Evaluation of these equilibrium equations by the method of least squares provides the best unbiased estimates for the standard thermodynamic function changes and their standard errors which are readily determined for the first time. Application of the equations to the ionization of aqueous cyanoacetic acid furnishes a more general representation of the data than comparable empirical relations. Use of the new equations is recommended when it is required to predict both the values and errors on standard thermodynamic function changes from the temperature dependence of reaction equilibrium constants.
528 citations
TL;DR: Experimental results obtained on six different electrodes are in excellent agreement with the predicted values of N, the collection efficiency of a ring disc electrode, and the new theory is compared with an earlier approximate treatment.
Abstract: A fundamental parameter for a ring disc electrode is N, the collection efficiency. An exact solution for N is derived by rigorously solving the convective diffusion equation with the proper boundary conditions. Experimental results obtained on six different electrodes are in excellent agreement with the predicted values of N. The new theory is compared with an earlier approximate treatment which, depending on the electrode geometry, may lead to errors of up to 25 %.
222 citations
TL;DR: In this article, a series of homologous tetraalkylammonium chlorides, bromides and iodides have been measured precisely by means of a differential buoyancy technique, down to 0.01 m.
Abstract: The apparent molal volumes ϕV of a series of homologous tetraalkylammonium chlorides, bromides and iodides have been measured precisely by means of a differential buoyancy technique, down to 0.01 m. The values of ϕV extrapolated to infinite dilution give partial molal volumes text-decoration:overlineV°s which are almost additive for successive homologues and enable the absolute individual partial molal volumes of the halide ions to be estimated by a new principle to an accuracy of about 0.5 ml mole–1. The concentration dependence of ϕV and text-decoration:overlineVs is anomalously large and negative, and possible origins of the effects observed are examined. In particular, the distance of closest approach, mutual salting-out associated with the large size of the ions and mutual salting-in arising from the hydrophobic character of the cations, are suggested as some of the reasons for the anomalies in the partial molal volume and activity coefficient behaviour which are exhibited by these salts.
219 citations
TL;DR: In this paper, the infrared spectra of decationated X-and Y-type zeolites were analyzed for adsorption isotherms, calculated from the spectra and superimposed on those determined by volumetric techniques, showing that the strongest interaction was with the acidic hydroxyl groups and most of the adsorbed C2H4 was hydrogen-bonded to these.
Abstract: Three OH stretching bands, with maxima at about 3745, 3650 and 3545 cm–1, are present in infrared spectra of decationated X- and Y-type zeolites. Pyridine reacted with the 3650 cm–1 species to form pyridinium ion. This band underwent a hydrogen-bonding shift when ethylene was adsorbed at room temperature, indicating a strong physical adsorption which was quantitatively and rapidly reversible on raising or lowering the pressure. No exchange occurred between C2H4 and the OD groups of an exhaustively deuterated zeolite. The hydrogen-bonding shift from 3650 to 3300 cm–1 was identical when C2D4 was substituted for C2H4. The 3745 and 3545 cm–1 bands were not noticeably altered by the adsorption, at least in the pressure region where the 3650 cm–1 band was affected. Adsorption isotherms, calculated from the spectra, could be superimposed on those determined by volumetric techniques. Both were close to Langmuir-type but showed evidence of a superimposed non-selective adsorption at higher pressures. Ethylene may also adsorb, via a charge-transfer interaction, on the residual Na+ ions of the zeolite. At about 500 torr, the total adsorption of C2H4 was about 30 % greater than the available zeolite hydroxyl groups. It was inferred that the strongest interaction was with the acidic hydroxyl groups and that, at low pressures, most of the adsorbed C2H4 was hydrogen-bonded to these. In the CH bending and stretching regions, only the Q-branch of the spectra of the gaseous molecules appeared, indicating that molecular rotation was hindered in the adsorbed state. Qualitatively similar results were obtained with C3H6. The hydrogen-bonding shift was greater by about 100 cm–1, however, and the adsorption was not entirely reversible. Moreover, the irreversible portion increased with time, and products stemming from polymerized olefin could be recovered; also, C3D6 exchanged with the OH groups of the 3650 and 3545 cm–1 bands, but not with those of the 3745 cm–1 band. Preliminary results for these substrates adsorbed on dehydroxylated, decationated zeolites are given.
152 citations
TL;DR: The phase diagram of the KI+AgI system has been redetermined and two intermediate compounds have been identified as discussed by the authors, KAg4I5 and K2AgI3.
Abstract: The phase diagram of the KI+AgI system has been redetermined. Two intermediate compounds have been identified. K2AgI3 is stable up to 130°C. At higher temperatures it undergoes a solid state disproportionation reaction to KAg4I5 and KI. KAg4I5 is stable between its incongruent melting point (253°C) and 38°C. At lower temperatures it disproportionates to β-AgI and K2AgI3. A eutectic between KAg4I5 and KI occurs at a nominal composition of 29.5 mole % KI and 238°C. The compound KAg4I5 has an exceptionally high ionic conductivity for a solid, reaching 0.31 ohm–1 cm–1 at the incongruent melting point. The current is carried by the Ag+ ions. Thermodynamic data derived from e.m.f. measurements indicate that the formation of KAg4I5 from K2AgI3 and AgI is accompanied by an entropy gain, implying an unusually high degree of disorder in KAg4I5.
137 citations
TL;DR: In this paper, a study of the adsorption of homogeneous non-ionic detergents from aqueous solution on Graphon has been made, where the authors attributed the temperature-dependent hydration of the molecules to the adsorbate + adsorbent interactions, the effect of which becomes progressively more pronounced as the lower consolute phase boundary is approached.
Abstract: A study has been made of the adsorption of homogeneous non-ionic detergents from aqueous solution on Graphon. At a fixed temperature maximum adsorption increases with increasing alkyl chain length and diminishes with increasing size of the hydrophilic head group. In contrast to the behaviour normally observed for the adsorption of a single component, the adsorption of these compounds from soution increases with increasing temperature. This effect has been ascribed to the temperature-dependent hydration of the molecules and, in general, their adsorption behaviour is influenced not only by the conventional adsorbate + adsorbent interactions, but also by solute + solvent interactions, the effect of the latter becoming progressively more pronounced as the lower consolute phase boundary is approached.
120 citations
TL;DR: In this article, the surface tension data were obtained by the method of differential capillary rise on the binary systems N 2+ Ar and N2+ CO at 83.82°K, and on the systems n2+ CH4, Ar + CH 4, and CO + CH4 at 90.67°K.
Abstract: Surface tension data have been obtained by the method of differential capillary rise on the binary systems N2+ Ar and N2+ CO at 83.82°K, and on the systems N2+ CH4, Ar + CH4, and CO + CH4 at 90.67°K. Thermodynamic equations are presented for the prediction of the surface tensions of simple mixtures, in which the surface phase is considered to be a regular solution. Their use is illustrated for the five systems studied.
118 citations
TL;DR: In this article, the dielectric relaxation in polyethyl methacrylate has been studied over a wide range of frequency, temperature and pressure (up to 3000 atm). Three relaxation regions α, β and (αβ) were observed.
Abstract: The dielectric relaxation in polyethyl methacrylate has been studied over a wide range of frequency, temperature and pressure (up to 3000 atm). Three relaxation regions α, β and (αβ) were observed. The α relaxation moved rapidly to lower frequencies with increased pressure, whereas the β relaxation was quite insensitive in location to this variable. The (αβ) relaxation was split into α and β processes with increased pressure. The α relaxation in polyethyl acrylate moved rapidly and continuously to lower frequencies as pressure was increased.
The α, β and (αβ) relaxations are discussed in terms of molecular mechanisms. A comparison of dipole relaxations in the alkyl methacrylate series must be made with caution in view of the α and (αβ) relaxations which occur in these polymers.
116 citations
TL;DR: The theoretical treatment of Kuhn and Grun has been employed to calculate the polarizability of the random link and the number of effective cross-links per molecular chain this article.
Abstract: At temperatures above the glass transition, amorphous polyethylene terephthalate fibres have been shown to possess optical and mechanical properties identical with those for a rubber. Thus, both the stress and the optical anisotropy may be directly related to strain (conveniently determined by the degree of retraction or shrinkage of pre-oriented fibres). The theoretical treatment of Kuhn and Grun has been employed to calculate the polarizability of the random link and the number of effective cross-links per molecular chain.
Additionally, measurements have been made of the decay of stress and optical anisotropy (birefringence) in water at various temperatures and as expected for a rubber-like network both decay at identical rates. Moreover, the decay curves for different temperatures can be superimposed by a simple frequency shift. The shift factors as a function of temperature fit the Williams-Landel-Ferry equation.
TL;DR: When catalytic aluminas are heated to a high temperature, sites are produced on the surface which are capable, at room temperature, of oxidizing polynuclear aromatic hydrocarbons to the corresponding ion-radical, provided oxygen is present as mentioned in this paper.
Abstract: When catalytic aluminas are heated to a high temperature, sites are produced on the surface which are capable, at room temperature, of oxidizing polynuclear aromatic hydrocarbons to the corresponding ion-radical, provided oxygen is present. The oxidizing activity depends markedly on the conditions of activation. Fully dehydrated alumina (corundum) is inactive as is alumina dehydrated below 320°C. Maximum activity occurs in samples heated to about 900°C in which the crystalline phase is identified as γ-alumina. The sites responsible for electron-transfer on the alumina surface differ in important respects from the characteristic oxidizing centres on silica-alumina, although in some silica-alumina catalysts both types of site may be present. The site, which is characteristic of alumina itself, involves molecular oxygen. Hydrocarbons adsorbed on this type of site react rapidly with oxygen and cannot readily be recovered unchanged from the catalyst surface. A second type of active centre predominates in the silica-aluminas of low alumina content. On this type of site the adsorbed hydrocarbon is stable for long periods. The electron acceptor at the latter site may be the SiO4 residue which occurs at the alumina-silica domain boundary. In the active oxidizing centre of the alumina type an oxygen molecule may occupy this role.
TL;DR: In this paper, the conditions under which the two black films are formed by solutions of sodium dodecyl sulphate in the presence of NaCl are established and the effect of several additives upon the relative stability of these two films is investigated.
Abstract: The conditions under which the two black films—the first of greater and variable thickness and the second of about 44 A—are formed by solutions of sodium dodecyl sulphate in the presence of NaCl are established and the effect of several additives upon the relative stability of these two films is investigated. Specific effects of counterions upon this behaviour are marked and are interpreted in terms of an ionic size effect upon the structure of the second black film and of preferential surface adsorption. Some conclusions about the composition and heat of formation of the second black film are drawn using Le Chatelier's principle. At higher ionic strengths counterions have also specific effects upon the thickness of the first black film in line with their hydrated size and adsorption.
TL;DR: In this paper, the excess volume of mixing as a function of composition has been measured at 40°C for mixtures of hexafluorobenzene with eight hydrocarbons, cyclohexane, cycloehexene, 1,3-cyclohexadiene, benzene, toluene, p-xylene, mesitylene, and cumene.
Abstract: The excess volume of mixing as a function of composition has been measured at 40°C for mixtures of hexafluorobenzene with eight hydrocarbons, cyclohexane, cyclohexene, 1,3-cyclohexadiene, benzene, toluene, p-xylene, mesitylene, and cumene. The results indicate that the fluorocarbon forms complexes with the hydrocarbons to an increasing extent as the electrondonating power of the hydrocarbon is increased. In an attempt to elucidate the nature of the complexing, the dipole moment of hexafluorobenzene has been measured in solutions of cyclohexane, benzene, p-xylene and mesitylene. The results are inconclusive but it is probable that any intermolecular bonding due to charge transfer interaction is extremely weak.
TL;DR: In this article, the relative intensities and lifetimes of the P-type delayed fluorescence of the same acceptor compound sensitized by two donor compounds were measured and the ratio of the triplet formation efficiencies of the two donors compounds was calculated.
Abstract: Measurement of the relative intensities and lifetimes of the P-type delayed fluorescence of the same acceptor compound sensitized by two donor compounds allows the ratio of the triplet formation efficiencies of the two donor compounds to be calculated. The method has been applied to a selection of aromatic hydrocarbons using perylene as acceptor and anthracene as the standard donor. With five of the six compounds studied, the sum of the triplet formation efficiency and the fluorescence efficiency exceeds 0.9. The results are compared with previous data and the application of triplet formation efficiencies to the calculation of other photochemical parameters is briefly discussed.
TL;DR: In this paper, the effects of acidity of acceptor and the basicity of the donor on the thermodynamics of hydrogen bonding have been investigated and relations between ΔH°, ΔνOH, ΔF° and other parameters have been discussed.
Abstract: Hydrogen bonding between various donors and acceptors has been investigated by employing infra-red, n.m.r. and electronic spectroscopy. The effects of acidity of the acceptor and the basicity of the donor on the thermodynamics of hydrogen bonding have been investigated. The relations between ΔH°, ΔνOH, ΔF° and other parameters have been discussed.
TL;DR: The variation of surface tension with temperature has been determined for several cryogenic fluids as discussed by the authors, including nitrogen, argon, carbon monoxide and methane, by using the theory of corresponding states.
Abstract: The variation of surface tension with temperature has been determined for several cryogenic fluids. Differential capillary rise measurements have been performed on nitrogen, argon, carbon monoxide and methane. From these as well as previous measurements, parameters of the Ferguson and Guggenheim equations have been calculated from experimental data on nine cryogenic fluids. The surface tensions of simple liquids are considered with reference to the theory of corresponding states.
TL;DR: In this article, an infra-red study of the surface of rutile has been carried out as a function of evacuation temperature (100-500°), and the surface was found to be composed of isolated and hydrogen-bonded OH groups, molecular water being removed by evacuation at temperatures 200°.
Abstract: An infra-red study of the surface of rutile has been carried out as a function of evacuation temperature (100–500°). Below 400° the surface was found to be composed of isolated and hydrogen bonded OH groups, molecular water being removed by evacuation at temperatures 200°. Above ca. 300° the hydrogen-bonded OH groups were progressively removed, the 450°-treated surface containing only isolated OH groups with a stretching frequency of 3740 cm–1. Absence of oxygen treatment of the surface after high-temperature evacuation markedly affects the OH region of the spectra. Rehydration experiments showed a strong interaction of the evacuated surface with water molecules but it has not been possible to decide conclusively whether surface OH groups are reformed on a 450°-treated surface.
TL;DR: In this article, the electrophoretic mobility of sols and suspensions of silver iodide has been investigated in the presence of a series of homogeneous non-ionic detergents of the alkyl polyoxyethylene glycol monocther type.
Abstract: The electrophoretic mobility of sols and suspensions of silver iodide has been investigated in the presence of a series of homogeneous non-ionic detergents of the alkyl polyoxyethylene glycol monocther type. Just before the critical micelle concentration of the non-ionic detergent was reached a pronounced decrease in the mobility of the particles was observed. Adsorption isotherms of the alkyl hexaoxyethylene glycol monoethers on silver iodide powder also showed a pronounced increase in adsorption in the same concentration region. The changes were consistent with the formation of a multilayer of non-ionic detergent on the surface which caused a displacement of the electro-kinetic plane of shear away from the surface. Adsorption of non-ionic detergent at the silver iodide/solution interface inhibited the adsorption of lanthanum, barium and sulphate ions.
TL;DR: In this paper, an explanation for the occurrence of "neat" and "middle" phases in mixtures of fatty acid salts and water is proposed to explain the transition between two forms as well as the following changes in size within a phase.
Abstract: An explanation is proposed to account for the occurrence of “neat” and “middle” phases in mixtures of fatty acid salts and water. The method consists of calculating differences in the electrostatic free energies of charging and in the water-hydrocarbon interaction free energies for these two liquid-crystalline structures. There is notable success in describing the transition between the two forms as well as in the following changes in size within a phase. Extension of the present work to biological materials is suggested.
TL;DR: In this paper, seven aromatic azides were photolyzed in organic matrices at 77°K and their primary photoproducts are stabilized and their spectra can be recorded, showing the general features associated with open shell aromatic structures, they are independent of the solvent and they disappear when the matrix is softened even at low temperature (90°K).
Abstract: Seven aromatic azides were photolyzed in organic matrices at 77°K The primary photoproducts are stabilized and their spectra can be recorded These primary spectra are assigned to nitrenes; they show the general features associated with open shell aromatic structures, they are independent of the solvent and they disappear when the matrix is softened even at low temperature (90°K) Band assignments for the spectra of the nitrenes and their parent azides are given The effect of nitrogen on the spectrum of the aromatic radical is discussed in terms of the concepts of Dewar and Longuet-Higgins
TL;DR: In this article, the authors examined the effects of homogeneously decomposing intermediate generated on the disc electrode and showed that the collection efficiency at the ring electrode will be reduced if the intermediate is homogeneous in the solution.
Abstract: If an intermediate generated on the disc electrode decomposes homogeneously in the solution, then the collection efficiency at the ring electrode will be reduced. This paper examines the effects of such a decomposition which takes place by first-order kinetics. For thin-ring, thin-gap electrodes, two limiting solutions are obtained; one when the collection efficiency is very small corresponding to most of the generated material being lost by reaction, and the other when the collection efficiency is close to N, the kinetic loss being small. It is also demonstrated that for any particular electrode the collection efficiency is a function only of (kν⅓D–⅓ω–1).
TL;DR: In this paper, the solubility of xenon in 95 % ethanol was shown to be sufficient to quench the fluorescence of aromatic hydrocarbons with high efficiency, due to catalyzed intersystem crossing from the first excited singlet state eventually producing the lowest triplet state.
Abstract: The solubility of xenon in 95 % ethanol is shown to be sufficient to quench the fluorescence of aromatic hydrocarbons with high efficiency. Quenching is due to catalyzed intersystem crossing from the first excited singlet state eventually producing the lowest triplet state. Quenching constants are given for nine molecules and the quantum yields ϕT of triplet state production of pyrene and 9-phenylanthracene in 95 % ethanol have been measured. Xenon gas is shown to be an ideal fluorescence quencher for determining ϕT in solution.
TL;DR: In this paper, the mixed virial coefficients B12 were predicted for twenty-eight mixtures where experimental values have been reported, using both the Hudson and McCoubrey combining rule and the geometric mean rule for the critical temperatures.
Abstract: Values of the mixed virial coefficients B12 are predicted for twenty-eight mixtures where experimental values have been reported. McGlashan and Potter's reduced equation of state is used to calculate corresponding states values, Hudson and McCoubrey's combining rules being used for the mixed critical temperatures. A comparison is made between the experimental and predicted values, using both the Hudson and McCoubrey combining rule and the geometric mean rule for the critical temperatures. In the first six mixtures examined, which are a particularly good test of the procedure (because of differences in ionization potential and size of the two components), agreement is often obtained within the experimental error. In the case of the other twenty-two mixtures, sixteen are better represented by the new procedure.
TL;DR: In this paper, hydrogen contents were determined by outgassing specimens in vacuo, and also from considerations of the changes of E and R/R0 with time, under conditions where the absorption and/or desorption of hydrogen was governed by the diffusion of either hydrogen or oxygen molecules, through the Brunner-Nernst layer.
Abstract: Electrode potentials E and relative electrical resistance R/R0 were measured whilst hydrogen was both absorbed and desorbed by palladium-rich Pd+Ni and Pd+Rh alloys immersed in aqueous solutions at temperatures within the range 0–50°C. Hydrogen contents were determined by outgassing specimens in vacuo, and also from considerations of the changes of E and R/R0 with time, under conditions where the absorption and/or desorption of hydrogen was governed by the diffusion of either hydrogen or oxygen molecules, through the Brunner-Nernst layer. From the relationships obtained between E, R/R0 and hydrogen content, further relationships also were derived between hydrogen content and hydride vapour pressure p. The relationships between hydrogen content and the other parameters generally were found to exhibit an absorption/desorption hysteresis.
TL;DR: In this article, the electrical conductivity of water, compressed by explosively driven shock waves, has been measured in the experimentally difficult range of relatively low pressures (20-100 kbars).
Abstract: The electrical conductivity of water, compressed by explosively driven shock waves, has been measured in the experimentally difficult range of relatively low pressures (20–100 kbars). The results link the earlier high-pressure data of David and Hamann and of Yuknavech with the results of static experiments at much lower pressures. They confirm that the high conductivity of shocked water arises from enhancement of the normal self-ionization of water. In addition, experiments have been carried out to determine the effects of changing the initial temperature of the water, and to compare the behaviour of shocked D2O with that of H2O.
TL;DR: In this article, the intermolecular vibration band has been identified in the far infra-red spectra of the pyridine IBr and Pyridine ICI charge transfer complexes.
Abstract: The intermolecular vibration band has been identified in the far infra-red spectra of the pyridine IBr and pyridine ICI charge transfer complexes. All the reported observations on these and similar complexes can be accounted by a simple 3-centre molecular orbital treatment.
TL;DR: In this article, the results of impedance measurements at zinc electrodes in alkali were presented and the effects of adsorption at these electrodes were discussed and it was shown that zinc electrodes of different metallurgical histories display corresponding differences in reactivity.
Abstract: The results of impedance measurements at zinc electrodes in alkali are presented. The effects of adsorption at these electrodes are discussed and it is shown that zinc electrodes of different metallurgical histories display corresponding differences in reactivity.
TL;DR: Experimental phase diagrams have been obtained for binary mixtures of hexafluorobenzene with six hydrocarbons, benzene, toluene, p-xylene, mesitylene, cyclohexane and n-hexane as mentioned in this paper.
Abstract: Experimental phase diagrams have been obtained for binary mixtures of hexafluorobenzene with six hydrocarbons, benzene, toluene, p-xylene, mesitylene, cyclohexane and n-hexane. The first four systems all form well-defined 1:1 molecular complexes with congruent melting points. The mixture containing cyclohexane forms three much weaker complexes with incongruent melting points and compositions corresponding to a molar ratio of hexafluorobenzene to cyclohexane of 3:1, 5:1 and probably 6:1. Hexafluorobenzene forms a simple eutectic with n-hexane and an analysis of the experimental phase diagram indicates that the system exhibits a considerable positive deviation from ideality.
TL;DR: In this article, the authors show that photochemical changes may result from the absorption of light by metastable excited (triplet) states in rigid aliphatic hydrocarbon glasses, and that two processes occur: ionization of the solute and sensitized dissociation of the solvent to give free radicals (detectable by electron spin resonance) and hydrogen atoms.
Abstract: Under certain conditions, photochemical changes may result from the absorption of light by metastable excited (triplet) states. In solutions of aromatic compounds in rigid aliphatic hydrocarbon glasses, two such processes occur: these are the ionization of the solute (detectable by thermo-luminescence on subsequent heating) and sensitized dissociation of the solvent to give free radicals (detectable by electron spin resonance) and hydrogen atoms: the latter are not trapped but abstract another hydrogen atom from the solvent or the solute, so that the production of solute radicals (e.g., benzyl from toluene) is also biphotonic.