Journal Articles (before-1995)
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/16938
Browse
6 results
Search Results
Item Influence of Pressure on the Ionization of Substituted Phenols(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (12), 1974) Hamann, Seffon D.; Linton, MaxSpectroscopic measurements have been made of the ionization constants of eighteen substituted phenols in water at 25°C and at 1, 500, 1000, 1500 and 2000 bar. Ionization of the phenols is enhanced by an increase of pressure, and the derived values of the change in partial molar volume for ionization lie between –8 and –20 cm3 mol–1. The results are discussed in terms of the molecular structures of the phenols.Item Use of a Rotating Single Probe in Studies of Ionization of Additives to Premixed Flames: Part 5.—Recombination of Metal Ions with Electrons(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Anthony, Edward J.; Bulewicz, Elzbieta M.; Kelly, Roy; Padley, Peter J.Electrostatic probe measurements are reported on the recombination rate constant, kr, or the process M++ e–X→M + X in premixed flames, for a number of metals M and (for M = Li) for the specific collision partners ×= H2, Ar, CO, CO2, H2O, N2. The results confirm, in all important respects, previous independent observations and inferences on this process, including the conclusion that the recombination cross-section is not markedly dependent on the nature of X. In addition, the sensitive probe procedure employed reveals aspects of kr, with respect to dependence on no fewer than three variables, temperature, composition and ion concentration, which will require mass spectrometric investigation before they can be fully understood.Item Enthalpy of Ionization of Water from Electro-motive Force Measurements(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (5), 1973) Bezboruah, Chitra P.; Camoes, M. Filomena G. F. C.; Covington, Arthur K.New e.m.f. data have been obtained for the cell: Pt, H2|NaOH, NaCl|AgCl|Ag, over the temperature range 5–85°C, from which values of the ionic product (Kw) and the enthalpy of ionization of water (ΔH°) can be calculated. A general expression is given for the standard error in the enthalpy of ionization (ΔH°) in terms of the errors of the parameters of the general polynomial-logarithmic equations used to represent the variation of ionization constant (K) with temperature. The standard error in ΔH° has only been calculated previously for certain polynomial expansions, such as the Clarke and Glew equations. Selected data for the ionization constant of water derived from e.m.f. measurements have been analysed with various pK =f(T) expressions to establish the standard error in ΔH° from each, and to determine whether the reported discrepancy of 200 cal mol–1 between ΔH° derived calorimetrically and from e.m.f. measurements can arise from the method of analysing the pK data. It is concluded that only systematic errors and not statistical errors in the e.m.f. data can account for the discrepancy. The extrapolation of the e.m.f. results to zero ionic strength to obtain Kw is suggested as the most likely cause of the discrepancy between the e.m.f.-derived and calorimetric ΔH° valuesItem Ionization of Moderately Strong Acids in Aqueous Solution: Part 2—Further E.m.f. Studies of the Dissociation of the Bisulphatc Ion(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (1), 1973) Covington, A. K.; Dobson, J. V.; Srinivasan, K. V.New measurements on the cell: Pt,H2 | Na2SO4, NaHS04, NaCl | AgCl | Ag have failed to substantiate the original measurements made by Hamer forty years ago and subsequently reanalyscd many times. The range of values for the dissociation constant of the bisulphatc ion (K2 of sulphuric acid) is substantially in agreement with that obtained from the simpler cell in which sodium chloride was omitted and the mercury-mercury(I) sulphate reference electrode was used. K2 = 0.0113 ±0.0005 mol kg-1 at 25°C where the uncertainty arises from a range of reasonable choices for the ion-size parameter.Item Kinetic isotope effects: Part 7.—Ionization of (d)-phenylmethylacetophenone(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (5), 1972) Earls, D. W.; Jones, J. R.; Rumney, T. G.Measurements are reported on the hydroxidc-catalyzed ionization of (d)-phenylmethylaceto- phenone in the presence of varying amounts of dimethyl sulphoxide. The kinetic hydrogen isotope effect (kn/kr) increases with increasing basicity until at a H_ value of 16.5 it reaches a maximum. The value of the Bronsted exponent 3 is 0.49 ±0.02 for both isotopes. For several media, activation energies and pre-cxponcntial factors have been determined. The difference Ey—Er reaches a maximum at a H_ value of 16.8. The ratios of JrMt reflect the importance of solvent reorganization contributions.Item Energy Partition in the y-Radiolysis of Gaseous H2S+N2, H2S+Ar and H2S+Xe Mixtures(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (10), 1972) Ahmad, M.; Huyton, D. W.; Woodward, T. W.Ionization measurements in H24-N2, H2S4-Ar, and H2S4-Xc mixtures arc used to determine apparent stopping power ratios for the mixtures, or “ energy partition parameters ”. The values found for H2S4- N2, H2S4-Ar, and H2S4-Xc are 0.20, 0.95, and 3.60 respectively, as compared to the calculated values of 0.82, 0.95, and 2.46. In H2S4-Ar mixtures a “Jesse effect ” is observed that increases the ion yield by 2 units, this effect being quenched out between stopping power fractions Z = 0.2-0.4. Measurement of sulphur yields in H2S4-N2 mixtures enables an energy partition parameter of 0.5 to be evaluated. The difference from the value obtained by ionization measurements being explained by a small “Jesse effect" In H2S4-Ar mixtures the sulphur yield G(S) was always >G(S) = 7.0 found in pure H2S and approached values as high as 24. The sulphur yield also increased between Z = 0.2 and 0.4 by twice the decrease in the ion yield. G(S) in H2S4-Xe mixtures never rises above 7.0, and the values can be justified by energy transfer from Xe* (G ~ 5.0) to H2S to give H2 4- S*, where S* is not a ground state S(3P) atom. No such simple mechanism will explain the results in H2S4-Ar mixtures. Butadiene was used as an SH and S(3P) scavenger, and the ratio of scavengeablc to non-scavengcablc sulphur in H2 4-Ar mixtures is similar to that in H2S i.e. ^43. In H2S4-Xc mixtures this ratio is ~3-4, and is explained by production of excited S atoms (S*), which react with H2S to give H2 and S2.