The surface tension of polyoxyethylene glycol in water leads to a value for the area per molecule which shows that the polymer molecules lie approximately flat in the surface. Molecular weight determinations by end‐group analysis and freezing‐point depression are compared with values of the intrinsic viscosity and limiting area per molecule.

The diffusion coefficients in water of ethylene glycol and several poly(ethy1ene oxides) of low molecular weight have been measured at 15, 25 and 35°C. The activation energies of diffusion are in the range 19-21 kJ mol-' in agreement with published results on more rigid molecules. The Stokes-Einstein diffusion radii increase with temperature probably as a result of conformational changes in the polyoxyethylene chain. After allowing for hydrogen bonding of water molecules at the terminal hydroxyl groups, the diffusion coefficients are found to be inversely proportional to the root mean square distance (F)+ of a chain element from the molecular centre of mass. This relationship holds over the whole molecular weight range studied, and no evidence for free-draining is found.Comparison with the theory of Kirkwood and Riseman shows that the actual value of (?)* is 1.95

The activation energy of the parahydrogen conversion on palladium-rich alloys is 3-5 kcal./mole and increases abruptly between 40 and 30 atomic per cent. palladium t o the value of 8-5 kcal. found for gold-rich alloys. Magnetic measurements have identified this composition as corresponding t o the complete filling of the d-band, or atomic d-orbitals, with electrons. Vacant d-orbitals are therefore essential for the low-temperature catalysis, and it is suggested that they bond the chemisorbed hydrogen atoms M-H.The reaction goes through a triatomic H, complex formed by entry of an H, molecule from the van der Waals layer,It is postulated that each site exerts two bonds t o the activated complex, employing " atomic " d and hybrid d2.56 sP*.*~ metallic orbitals. The values of temperature-independent factor found agree with earlier calculations for this mechanism. The d-band of palladium may also be filled by electrons from dissolved hydrogen atoms which cause a similar increase in activation energy.This work 1 was initiated in Bristol University in 1945 in an attempt to relate the activity of transition metal catalysts to their electronic structure. I n the past various efforts have been made to provide a theoretical basis for catalyst activity, by relating catalytic activity to lattice spacing. Thus, on the experimental side there are the papers by Balandin,2 Long et aZ.,3 Twigg, Herington and Rideal,'~ 6 and Beeck and his co-workers.6B 7 On the theoretical side, calculations of the chemisorption of hydrogen molecules by the Eyring-Polanyi method indicate a marked effect of the lattice-spacing in the surface on the activation energy of the process.** @ Recent advances in our knowledge of the metallic state now make it possible to begin a more fundamental approach to the problem, and to attempt to relate catalyst activity t o the nature and occupation of the electronic energy levels of the catalyst. All those metals active as hydrogenation catalysts fall into the group of transition elements, with the exception of copper which, in general, has a higher activation energy than the others. The atoms of these elements possess partly empty d-shells and the theory of the bulk metal may be treated by either of two methods. The first method, due to Mott and * Part I in a series of papers on the Electronic Basis of Catalyst Activity.

Measurements have been made of the surface tension of solutions of sodium dodecyl sulphate, dodecyltrimethylammonium bromide, decanol, and of n-dodecyl and n-tetradecyl hexaoxyethylene monoethers in pure formamide and in salt solutions. Adsorbed films of the ionic surfactants exert low surface pressures (about 15 mN m-1 near the solubility limit) and exhibit no discontinuity characteristic of micellar aggregation. The monoethers exert surface pressures up to 25 mN m-I and show a critical micelle concentration of 0.039 mol dm-3 (CI2E6) and 0.013 mol dm-3 (ClsEs) with aggregation numbers of about 40 and 64 respectively at 25°C. The lower surface activity and higher solubility of the surfactants in formamide compared with water indicate the lower stability of adsorbed and micellar states in the former solvent. Similarly the aggregation numbers of the micelles of monoethers in formamide are much lower than those in water.

Results are reported for measurements of the diffusion coefficients of poly(ethy1ene oxide) fractions in aqueous solution and of the viscosities and sedimentation coefficients at temperatures between 8 and 35"C, for molecular weights from 1000 to 6000. These show that the polymers behave in water as non-free-draining coiled molecules having dimensions which become less perturbed by the solvent as the temperature is lowered, the &temperature is estimated at 5°C. The unperturbed dimensions are seen to decrease with increasing temperature due possibly to greater freedom of rotation of the atoms around the bonds joining them. The entropy parameter, $, is about 0.36, coming within the range of geometrically good solvents.