Although Zachariasen was able to determine the gross structure of sodium bicarbonate, his assumptions preclude any conclusions to be drawn concerning the nature of the carbonate group itself. It is therefore the purpose of this paper to reinvestigate the sodium bicarbonate structure employing modern Weissenberg photography and least squares refinement techniques with particular emphasis placed on the determination of the carbonate group configuration. Zachariasen's parameters and bond distances will appear in conjunction with the results reported here to facilitate ease of comparison.

The problem set up as the objective of the present thesis is the detection and measurement of adiabatic thermal changes in barium titanate ceramic at low temperatures. Concurrent with this is the problem of devising experimental techniques suitable for the investigation of this phenomenon in other dielectrics at liquid helium temperatures, a temperature region in which no previous measurements of this type have been made.

Although it was in fact the study of the Wigner distribution function that suggested to the author the general problem discussed in Part I, a consideration of the question of the formation of quantum mechanical operators corresponding to dynamical variables, being of fundamental importance to quantum theory, should properly precede a discussion of the Wigner distribution function. In both Parts I and II spin and relativistic effects will be ignored. A word about notation is in order. A symbol such as A will denote the quantum mechanical operator corresponding to the dynamical quantity A. For example, H is the Hamiltonian operator; q is the coordinate operator and p the conjugate momentum operator. Whenever there is a possibility of confusion, O(A) is used to represent the operator corresponding to the dynamical quantity A. For example, O(pq) is the operator corresponding to the product pq, and O(H2) is the operator corresponding to the square of the classical Hamiltonian. A subscript appearing on a differential operator, such as in 66PH , indicates the function on which the operator acts. Unless otherwise indicated all integrations are to be taken from -infinity to infinity. As usual, h denotes Planck's constant divided by 2pi. Since any physical investigation is directly dependent on the quality of the tools used in the investigation, mathematical rigor is much to be desired in physical theory. That rigor has not been achieved in this work is all too obvious, but it was nonetheless a constant goal.

In the work which follows, the changes in structure of natural and electrolytic films brought about by various treatments will be the subject under discussion, and the experimental account will be concerned with the report of some effects encountered in the investigation of these oxide films. The confused and sometimes contradictory nature of the existing evidence regarding the nature and behavior of oxide films on aluminum is considered as sufficient justification for further study of the subject. It is hoped that some of the contradictory results obtained by other investigators may be explained on the basis of their experimental conditions and the interpretation of the data obtained.

The properties of pressure-induced flow of liquid helium II have been studied by the observation of the temperature and pressure dependence of the flow in narrow channels. The channels are in the form of an annular slit between two flat glass plates. Measurements of the flow rates have been made with hydrostatic pressures up to 2.3 x 103 dynes/cm 2, at temperatures between 1.39 and 2.10°K, and with slit widths of 2.4 and 4.3 microns. The observed flow rates have the same temperature dependence as the superfluid concentration in helium II. At lower pressure heads the flow rate is proportional to a power of the pressure head. The power is nearly independent of temperature but decreases with decreasing slit width. At higher pressures the flow rates reach saturation values at which they are independent of pressure. These saturation rates also have the temperature dependence of the superfluid concentration. The modifications necessary in the existing theories to explain these results are considered in a qualitative manner, and the need for further experiments of this nature is pointed out.

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The cooling of a surface when thermionic electrons are emitted has been measured by Richardson and others. The results obtained for tungsten and other metals are consistent with recent determinations of the work functions by thermionic and photoelectric methods. The purpose of the research, here described, was to determine the cooling of a surface when photoelectrons are emitted. In the determination of the cooling of a surface when photoelectrons are emitted, the small electron currents possible demand a very sensitive temperature measurement. A bolometer method similar to that used in the thermionic work was first tried but did not prove satisfactory; so this method was discarded, and thermocouples were used instead. Two similar photoelectric cells were illuminated with the same source of light. Each cell contained a small platinum plate coated with caesium, the temperature of which was measured with an Fe-Ni thermocouple. The thermocouple junctions of the two cells were connected in series with a galvanometer in such a manner that the e.m.f's of the two cells opposed each other. In this way it was possible to determine, with the galvanometer, the change in temperature when the photoelectric current was allowed to flow or was stopped in one of the cells. The photoelectric current was controlled by the potential of the anode.