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1Author    Albert Würflinger, Denise Mondieig3, Fazil Rajabalee3, MiquelAngel Cuevas-DiartebRequires cookie*
 Title    pVT Measurements and Related Studies on the Binary System /iC16H34 -tiC17H36 and on wC18H38 at High Pressures  
 Abstract    The phase diagram of the binary system nC16H34 -rcC17H36 has been established at ambient pressure using DSC and crystallographic measurements. At low temperatures below the rotator phase RI there exist two crystal forms Op (about jc(C17) = 0.25) and Mdci (about x(C17) = 0.67) which are different from the crystal structures of the pure compounds (Tp for C 16 and Oi for C 17). Furthermore two compositions: (a) C 16/C 17 = 3:1 and (b) = 1:2, which correspond to the coexistence range of Op and Mdci, were chosen for high pressure DTA and pVT measurements, yielding the following findings: The specific volume of the rotator phase of C 17 is distinctly lower than those of the binary systems at the same state point. Assuming the existence of a metastable rotator phase for C 16, an excess volume of A V E/V « 0.01 can be estimated. Due to the very enlarged coexistence range of RI, the mixtures reach their lower transition point at considerably lower temperatures (in isobaric measurements) or higher pressures (in isothermal measurements), where the specific volume is lower than that of C 17 at its transition point. Furthermore, the volume and enthalpy changes of the O ord -RI transition is distinctly smaller for the binary systems than for pure C 17. Thus the specific volumes of the phases Op and Mdci are appreciably larger than t>(spec.) of C 17. Op and Mdci have practically the same specific volume in accordance with the crystallographic results. Enthalpy values are obtained with the aid of the Clausius-Clapeyron equation which agree well with enthalpies derived from the DSC measurements. Furthermore, pVT data have been established for the liquid and solid phases of nC18H38 in the neighbourhood of the melting curve, allowing to determine volume and enthalpy changes of melting as a function of pressure. 
  Reference    Z. Naturforsch. 56a, 626—634 (2001); received July 18 2001 
  Published    2001 
  Keywords    Hexadecane, Heptadecane, Octadecane, pVT, Excess Volume, Phase Transition, High Pressure, X-ray 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0626.pdf 
 Identifier    ZNA-2001-56a-0626 
 Volume    56