Infrared spectra of surface complexes formed when CO and €12 are exposed at 20 and 180" to silica-supported iron have been obtained. The results are interpreted as indicating that: (a) no interaction takes place a t 20'; (b) complexes of the type H OH R-C--M are formed; (c) the surface is about 75% free to chemisorb CO even after 15 hr. of reaction at 180'; (d) CO is in rapid dynamic equilibria between the surface and gas phases; and (e) there is physically adsorbed as well as chemisorbed CO on the surface at 180'. These findings are in accord with the proposal that alcoholic intermediates are important in Fischer-Tropsch synthesis.

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spond to very weak complexes. Also, given the excellent correlation between the 'ß and the electrostatic energy parameters (<5Z) of the aromatic solutes (Figure 1), it seems unlikely that charge-transfer forces are important. If they were, one would expect a trend of increasing with increasing methylation of the aromatic ring (or decreasing "donor" ionization potential), which is not observed. Note the low value for mesitylene and the high values for the balobenzenes in Table IV. It is concluded, therefore, that the interactions present in these systems, whether they lead to long-lived complexes or short-lived contact interactions,23 are predominantly electrostatic in nature.Supplementary Material Available. Tables VI-IX will appear following these pages in the microfilm edition of this volume of the journal. These tables contain specific retention volumes (Vg°), infinite dilution activity coefficients (72" ), and interaction parameters ( ) at 30, 40, 50, and 60°for the 48 binary systems found in Table III. Photocopies of the supplementary material from this paper only or microfiche (105 X 148 mm, 24X reduction, negatives) containing all of the supplementary material for the papers in this issue may be obtained from the Journals Department, American Chemical Society, 1155 16th St.,

The infrared spectra of CO, CO,, 02, and HzO adsorbed on silica-supported iron at 20 and 180" have been obtained. Cheniisorbed CO and gas phase CO are in dynamic equilibrium at 180". Chemisorbed CO gives bands a t 4. 95, 5.05, and 5.3 p. Upon adsorption at 20", COS dissociates into chemisorbed CO and an oxide ion. Both 0 2 and H2O displace chemisorbed CO from the surface but do not give any bands themselves. At 180" adsorbed 02 gives a spectrum which is characteristic of iron oxide. A t 180" adsorbed water apparently completely dissociates since it gives no OH band. While COS gives no evidence of physical adsorption a t 20°, a t 180" it gives a band a t 4.3 p which is tentatively assigned as physically adsorbed COX. Either COS or a mixture of CO and Oz when heated to 180' give a surface complex with a band a t 6.5 p . This complex is tentatively assigned a carboxylate type structure.The association of chloroform and benzene has been investigated in the temperature range 25-75' by nuclear rriagnetic resonance spectroscopy. The equilibrium constant at 25' is 1.06 i . 0.30 (m.f.)-l and the enthalpy and entropy of association are -1.97 i 0.35 lrcal. mole-' arid -6.5 i . 0.5 cal. mole-' deg.-l, respectively A system involving thc solvent cyelohexane and a low, iixcd concentration of chloroform was chosen to minimize contributions from solvent effects t o chemical shifts. The vhemical shift (8bonzeno...r.hlorofonn -8ohlorofunn) due to hydrogen bond formation is 1.91 =k 0.40 p.p.m. From a comparablc' investigation of the association of chloroform and triethylamine, values of the equilibrium constant at 25", enthalpy, cntropy, and (6t,,otirylo,nlnaahloroforin -Bol,loroform) a t 25" are 4.2 =k 0.2 (in.f.)-l, -4.15 i . 0.20 Ircal. mule-', -11.0 cal. deg.-I, and -1.48 p.p.m., respectively.