Browsing by Author "Staveley, Lionel A. K."

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Thermodynamic Study of Disorder in Hexa-amminenickel(II) Iodide and Diamminenickel(II) Iodide
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (09), 1974) Worswick, Richard D.; Cowell, Janice C.; Staveley, Lionel A. K.
The heat capacity of crystalline nickel(II) iodide, diamminenickel(II) iodide and hexa-ammine-nickel(II) iodide has been determined from 10 to 300 K by conventional adiabatic low-temperature calorimetry, and from 300 to 550 K by differential scanning calorimetry. Measurements have also been made of (a) the heat of solution of the three salts in dilute acid at 298.15 K, (b) the ammonia dissociation pressure for the systems nickel iodide + diamminenickel iodide (from 490 to 523 K) and diamminenickel iodide + hexa-amminenickel iodide (from 469 to 503 K), (c) the magnetic susceptibility of nickel iodide and diamminenickel iodide from 4 to 230 K. The thermodynamic results have been used to obtain for the diammine and the hexammine two values of the molar entropy at 298.15 K, namely the third-law entropy Scal, and the entropy Seq derived from the appropriate equilibrium study. For each salt, Scal and Seq agree within experimental error, so that both salts appear to become completely ordered at 0 K. The implications of this result for hexa-amminenickel iodide are briefly discussed in the light of previous experimental and theoretical work on this salt.
Thermodynamic study of disorder in mercury(II) diamminodichloride and mercury(II) diamminodibromide
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Cooke, Michael D.; Linford, Roger G.; Staveley, Lionel A. K.; Worswick, Richard D.
In the salts mercury(II) diammino-dichloride and -dibromide the mercury atoms are positionally disordered at room temperature, the disorder being tantamount to that of dimers (the linear NH3—Hg—NH2+3 cations) on a cubic lattice. The heat capacity of the chloride has been measured from 3 to 300 K and that of the bromide from 10 to 300 K, giving the apparent (calorimetric) entropies of the salts at 298.15 K. The true (equilibrium) entropies at the same temperature have been determined by e.m.f. measurements on cells incorporating the complexes in the cell reaction, combined with previous measurements of the heat of solution of gaseous ammonia in the electrolytes used in the cells. A comparison of the entropy values shows that both salts retain entropy, and hence are still disordered, at the absolute zero. The value of the residual entropy for the chloride (considered to be the more accurate of the two) is 12.0 ± 3.0 J K–1 mol–1, and that for the bromide is 20.0 ± 7.5 J K–1 mol–1. These estimates of the residual entropy are briefly considered in the light of theoretical work on the disordered dimer problem. It seems likely that the residual entropy due to the disordered arrangement of the cations is supplemented by some degree of (possibly consequential) orientational disorder of the ammonia molecules.
Thermodynamics of Binary Liquid Mixtures Involving Hydrogen Bromide, Hydrogen Chloride and Xenon
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (04), 1978) Calado, Jorge C. G.; Gray, Christopher G.; Gubbins, Keith E.; Palavra, Antonio M. F.; Soares, Virgilio A. M.; Staveley, Lionel A. K.; Twu, Chorng-Horng
The total vapour pressure of the systems hydrogen bromide+xenon and hydrogen bromide + hydrogcn chloride have been measured as a function of composition at 195.42 K. The results have been used to estimate the excess Gibbs function GE. The volume of mixing J/E has been determined for each system at 195.42 K. The HBr + Xe system departs considerably from ideal behaviour, while HBr+HCl is only slightly nonideal. Neither system exhibits an azeotrope at the temperature studied. These results, together with similar data reported previously for the HCl + Xe system (J.C.S. Faraday I, 1975, 71, 1372), are compared with theoretical calculations based on perturbation theory for liquids of nonspherical molecules. Agreement is good for all three systems. The results show that both dipolar and quadrupolar forces for the 1-IC1 and HBr molecules have a large eifect on the phase diagram, while other types of anisotropic intermolecular forces (overlap, dispersion, induction) appear to have a considerably smaller effect.
Thermodynamics of the Liquid System Methane+Propane
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (08), 1974) Calado, Jorge C. G.; Garcia, Gerald A.; Staveley, Lionel A. K.
The total vapour pressure of liquid mixtures of methane and propane has been measured as a function of composition at temperatures of 115.77 and 134.83 K. The activity coefficient of methane f\ and the excess Gibbs function of mixing GB have been evaluated from the vapour pressure measure ments, and the heat of mixing and the excess entropy of mixing SE have been estimated from the temperature dependence of GE and compared with direct calorimetric values. Values of the excess thermodynamic functions have been calculated from a simplified version of the Flory theory of mixtures, with allowance for departures from the geometric mean (Berthelot) combining rule. Calculations show that these deviations are very small, but not negligible.