Journal Articles (before-1995)

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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.
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    Thermodynamic Study of Disorder in Zinc Fluoride Tetrahydrate
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (8), 1972) Cook, R O; Davies, A; Staveley, L A K
    The heat capacity of zinc fluoride tetrahydrate has been measured from 10 K to 300 K, giving a value for Scab the calorimetric entropy, at 25°C. The entropy Scq of this salt has been determined by studying the solution thermodynamics of zinc fluoride at 25°C. Seq exceeds SCal by 8.9±1.5 J K”1 mol-1, so that the crystalline tetrahydrate is disordered at 0 K, with a residual entropy of approximately/? In 3. The reason forthis disorder is believed to be that for iron(II) fluoride tetrahydrate at ordinary temperatures, namely that the metal atom is octahedrally surrounded by four water molecules and two fluorine atoms, and that the crystal does not distinguish between the oxygen and fluorine atoms. If the fluorine atoms in an octahedron are in a trans position to each other, each octahedron would have three possible orientations. To obtain an improved estimate of the standard entropy of the fluoride ion (needed in the evaluation of 5eq), the heat of solution of sodium fluoride in water at 25°C has been redetermined. This value, together with existing information on the salt and its saturated solution, gives —13.1+0.4 J K"1 mol-1 for the standard entropy of the fluoride ion at 25°C