The state of dissolved benzene in aqueous solution

Henry's law constants for benzene in water have been measured by bringing water layers into equilibrium with solutions of benzene in carbon tetrachloride or in cyclohexane. The mole fraction of benzene in the aqueous layer was determined by ultraviolet absorption spectrophotometry, and its fugacity was taken as equal to that in the nonaqueous phase, reliable data for the C₆H₆–CCl₄ and C₆H₆–c–C₆H₁₂ systems being available in the literature. Measurements were made at 5^o intervals from 10 to 30°C inclusive, at mole fractions down to from 10% to 20% of saturation. In no case did Henry's law constant depart significantly from constancy, and it was in reasonable agreement with some representative literature values based on saturated solubility. The constancy and the magnitudes of our K_h values indicate that appreciable dimerization does not occur in the temperature range examined here. This conclusion contrasts with the suggestion of Reid, Quickenden, and Franks that their calorimetrically measured heat of solution of benzene in water is different enough from the van't Hoff heat to imply possible dimerization of the solute; it also contrasts with the hydrophobic-bond-forming tendency which Ben-Naim, Wilf, and Yaacobi ascribe to benzene on the basis of their studies of the solubilities of benzene and biphenyl. The results of the latter study, when combined with the known second virial coefficient of benzene vapor, predict that more than 20% of the benzene in saturated aqueous solution at 25°C should be present as dimer, in clear contradiction to the results of the present work.     

High-resolution pattern replication using soft X rays

A soft X ray lithographic technique capable of contactless replication of submicrometre linewidth planar-device patterns is described. Special soft X ray exposure masks have been developed for the 4?14 ? wavelength region. Elastic-surface-wave-transducer patterns with 1.3 ?m electrode spacings were fabricated onto such masks using electron-beam techniques, and were successfully replicated.     

The expansion of the universe as a driving mechanism for the evolution of correlations

Viewed in the average comoving frame, a collection of galaxies evolves under the influence of time-dependent forces, and hence a time-dependent hamiltonian. This time dependence guarantees that, even if the universe were always spatially homogeneous and were completely free of correlations at some initial time, it would eventually develop large-amplitude correlations.     

Infinite median graphs, (0, 2)-graphs,and hypercubes

Hypercubes are characterized among connected bipartite graphs by interval conditions in several ways. These results are based on the following two facts: (i) connected bipartite graphs are median provided that all their intervals induce median graphs, and (ii) median (0, 2)-graphs are hypercubes. No cardinality restrictions are made.     

Conformational preferences of some substituted methyl groups in cyclohexanes as studied by carbon-13 nuclear magnetic resonance

Low temperature ¹³C NMR spectra of 80:20 mixtures of cis and trans-4? CH₃? CH₃? C₆H₁₀CH₂X, where ? C₆H₁₀-is 1, 4-disubtituted cyclohexyl and X=Br, CN, OH, OCH₃, Si(CH₃)₃, Sn(CH₃)₃, Pb(CH₃)₃ and HgOCOCH₃ have been recorded. The signals of the trans (e, e) components were assigned from the ambient temperature spectra of C₆H₁₁CH₂X and the established substituent effects of an equatorial methyl group in cyclohexane. Conformational equilibria of the cis (e, a?a, e) components were then computed from the intensities of the (remaining) signals (～180 K) of the two conformational isomers. From these equilibria A values of CH₂X were calculated, assuming additivity of conformational energies of CH₃ and CH₂X (the counter-poise approach). In general, these values are very similar to the value of the CH₃, although some trends do emerge. This study provides α, β, γ, and δ effects for a wide range of axial and equatorial ? CH₂X groups.