George E. Kimball

The Vapor Pressures of Some Alkali Halides

The vapor pressures of six alkali halides, NaBr, NaI, KI, CsCl, CsBr, and CsI, have been measured in the range from about 10−4‐mm to 0.1‐mm pressure. The measurements were made by the diffusion method, using an oxygen‐coated tungsten filament as detector.

The Electronic Structure of Diamond

The method of Wigner, Seitz and Slater has been applied to the determination of the electronic structure of diamond. It is found that the energy levels of the carbon atom are broadened into bands similar to the energy bands in metals. The 2s level of the atom splits into two bands, and the 2p level into six bands. The two 2s bands are completely filled by electrons and the two lowest of the 2p bands. The lowest unfilled band has a much higher energy than the highest filled band. The lack of electrical conductivity is explained and other properties of the diamond are discussed.

The effect of salts on the viscosity of solutions of polyacrylic acid

Abstract 1. 1. The viscosity of polyacrylic acid solutions has been studied as a function of concentration of added sodium chloride and degree of neutralization at a given concentration of polymer. 2. 2. The viscosity of PAA solutions has been measured as a function of concentration of sodium chloride and concentration of polymer at a given degree of neutralization. 3. 3. The effect of salts other than sodium chloride was found to depend on the charge and concentration of the cation rather than on ionic strength. A doubly charged cation is much more effective than a univalent positive ion. 4. 4. An empirical expression [1] was found to express the viscosity as a function of salt concentration which was valid at least for low salt concentrations. 5. 5. Empirical expressions were found for the variation of the parameter in the relationship mentioned in Item 4 with concentration of polymer. 6. 6. A comparison of the various theories explaining the behavior of PAA solutions was made.

The Quantum Mechanics of Seven and Eight Electrons with Spin Degeneracy

The eigenfunctions corresponding to the fourteen singlet states of a system of seven or eight electrons are given and the corresponding matrix elements tabulated in a form convenient for computation, neglecting multiple interchange integrals. Proof is given that the general method described in earlier work for writing bond eigenfunctions suffices to separate the multiplets. A method for calculating matrix components between bond eigenfunctions directly from the bond systems is also described.

Quantum Mechanics of the H3 Complex

A minimum energy and the associated nuclear configuration are given for linear symmetric H3 in the ground (2∑u+) state. An LCAO MO wave function with complete configuration interaction, is constructed from a set of five 1S hydrogen‐like orbitals with centers equally spaced on the line of nuclei. Apart from symmetry, nuclear positions and orbital centers are unrelated but the screening constant is the same for each orbital. The nonlinear parameters which were varied are the screening constant, internuclear distance, and the distance between adjacent orbital centers. An energy of —72.4±0.5 kcal/mole (relative to three separated H‐atoms) is obtained; the experimental value2 is ∼—103 kcal/mole.Many difficult 3‐ and 4‐center repulsion integrals were evaluated numerically, using the CPC at Watson Scientific Computing Laboratory. The chief advantage of this model is that all the difficult integrals belong to one family characterized by essentially three parameters. Thus, all of them were computed from a single n...

Ionization Processes on Tungsten Filaments II. The Absorption of Fluorine on Tungsten

Fluorine is found to form an adsorbed film on tungsten stable to temperatures above 2600°K. This causes a low accommodation for the thermal dissociation of fluorine. The adsorption is compared to that of oxygen on tungsten.

Bimolecular Association Reactions

By means of classical vibration theory a method is developed for estimating the mean lifetimes of the unstable molecules formed by the reaction of two polyatomic radicals. It is shown that these lifetimes are usually long in comparison with the time between collisions, except for the very simplest radicals. Approximate lifetimes for a number of these unstable molecules are given. From these values the orders of the corresponding association reactions may be predicted.

Overvoltage and the Structure of the Electrical Double Layer at a Hydrogen Electrode

The theory of absolute reaction rates applied to electrode processes leads to the equation s=(kT/h) exp (−ΔF*/RT) exp (αVF/RT) for the specific rate of discharge of ions. The question arises as to whether V should be the actual potential at the electrode or only the overvoltage. In the case of hydrogen ion discharge, it is found experimentally that the overvoltage should be used. On the other hand, the theory in its simplest form requires V to be the total potential. This paradox can be resolved by postulating the existence of two different electrical double layers at the electrode surface, and two corresponding energy barriers over which the protons must pass. Provided that the barrier nearer the electrode is the higher, the overvoltage is essentially established across this layer, while the variation in equilibrium potential caused by variations in the hydrogen ion concentration of the solution is established across the outer double layer. Since the rate of discharge is determined by the potential diffe...

Ionization Processes on Tungsten Filaments I. The Electron Affinity of the Oxygen Atom

The electron affinity of the oxygen atom was determined to be 53.8±0.8 kcal./mole by measuring the ratio of ions to electrons leaving a hot tungsten filament in contact with nitrous oxide gas at a low pressure. Previous investigations of this quantity yielded discordant results. A possible reason for this disagreement is set forth.

The Determination of Energy Levels from Thermodynamic Data. II. The Heights of Potential Energy Barriers Restricting Intramolecular Rotation

The uncertainty in the distribution of the energy levels implies a corresponding uncertainty in the shape of the associated potential energy function. The estimation of barrier heights is known to depend upon the shape of the potential, therefore implicitly upon the energy level distribution. We apply these ideas to the restricted rotation problem by introducing a shape parameter into the assumed potential function, and show that the currently accepted barrier height ranges should be widened. On the basis of our modified function, we found the following barrier heights to be consistent with published thermodynamic data: ethane 1550 to 2700 calories per mole; 1,1,1‐trifluoroethane 2300 to 8300; methanol 800 to 3000.