Excess volumes in the solutions benzene-h6/benzene-d6, cyclohexane-h12/benzene-h6, cyclohexane-h12/benzene-d6, and benzene-h6/benzene-d6/water

Abstract

Excess volumes are reported for the title solutions across the entire concentration range at 25 and 45 "C. For the solution of isotopic isomers, C&/C6&, the excess volume shows a complicated concentration dependence with a minimum of about -6 X m3/mol near X c , = 0.8 (25 "C). The effect is sensitive to trace water content. For benzene/cyclohexane solutions the volumetric isotope effects display simpler concentration dependences. Thus, the difference, pC6Hg/C6Hl2 -pCeDs,CsH12, within experimental error shows simple minima at Xbenzene = 0.5 of about -7 x (25 "C) and-12 x IO4 (45 "C) m3/moi. After comparing the present results for C6H6/C6H12 solutions with those of previous workers, we discuss isotope effects in terms of the theory of isotope effects on the properties of condensed phases.m3/mol near Xch = 0.33 and a maximum of about 2 x Experimental SectionDensities were measured with a Mettler-Parr DMA-60 vibrating densitometer using techniques previously described by us.&' The hydrocarbons were reagent grade and were further purified by fractional distillation. Deuteriocarbons were reagent grade. Tests for organic impurities in both hydrocarbon and deuteriocarbon samples were made by gas chromatography. The most likely impurity affecting the partial molar volumes is water. The problems which it introduces and our analysis of them are discussed at length in the next section. Hydrocarbons were kept on the vacuum line, over sodium, in closed vessels in the degassed state. In making up solutions, we transferred the degassed liquids via vacuum distillation into the mixing vessel and weighed them (still in the degassed state, i.e., Hook4) for the SOlUtiOnS C&j/C&,

Isothermal compressibility of benzene, deuteriobenzene (C6D6), cyclohexane, and deuteriocyclohexane (c-C6D12), and their mixtures from 0.1 to 35 Mpa at 288, 298, and 313 K

“…It will be shown in the next section that for purposes of comparison with model calculations it is useful to define the reciprocal reduced compressibility, kr~'. «r-1 = V/(kRT) (7) Figure 2. Relationship between the isotope effects on isothermal compressibility and those on molar volume at 298 K for the system C6H6 and c6d6.…”

“…For dopant concentrations on the order of 1% by weight, the effect on the polymerization transition is pronounced. In pure 7 Present address: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139. 0022-3654/84/2088-1040S01.50/0 sulfur there is a sharp rise in the weight fraction of polymerized sulfur,3 in the heat capacity,4•5 and in the viscosity6 above the polymerization transition at around 159 °C.…”

Chemical potentials of polymer blends from Monte Carlo simulations: consequences on SANS-determined .chi. parameters

“…Volume changes on mixing are assumed to be parabolic with a maximum difference of 0.05 % at a volume fraction of 0.5, a result that is in qualitative agreement with past experimental work. 78 Both positive and negative volumes on mixing are considered. It should be recognized that these state conditions represent typical numbers, and we utilize them to check if the experimentally observed composition dependences can be reproduced with the ideas presented here.…”

Isotope effects in solution thermodynamics: excess properties in solutions of isotopomers

“…29 The external Figure 6. Excess volumes of CgHg/CgDg solutions: (*,x,+) experimental points; solid curve = least-squares fit; (a) contribution of steric effect, random approximation; (b) steric effect, quasichemical approximation; (c) contribution of effect II, see text; (d) calculated total effect From ref 53 (courtesy of American Chemical Society). modes only make a small contribution to the partition function (and hence to MVIE).…”