Table of contents

The variation with composition of the lattice spacings of the solid solutions in tin of antimony, bismuth, lead, indium, cadmium, zinc and mercury has been determined. Antimony and bismuth decrease the axial ratio of white tin, while the other elements investigated increase the axial ratio. This suggests that the Brillouin zone for white tin is overlapped across planes of energy discontinuity which lie parallel to the tetragonal axis; the most probable form of this zone is discussed. The suggested Brillouin zone is bounded by planes of the (220) and (211) families, of which only the former are overlapped. The axial ratio variations may then be interpreted, and a possible explanation given for anomalies in the lattice spacing-composition curves for tin-indium and tin-cadmium alloys, which are associated with the development of vacant lattice sites.

A solution of the hydrodynamical equations for the case of Taylor instability for two fluids of constant density is sought by the method of successive approximations. The expansion parameter is the initial amplitude of the interface; the validity of the method then assumes convergence of the series involved. The linear equations to be solved at the pth step for the pth order unknown fields are derived. The solution is actually carried out up to the second approximation. An interesting feature of this solution is that its time growth comports not only the integral modes exp (σt) and exp (2σt) but also the irrational mode exp (radical2σt), in terms of the growth parameter σ identical with {gk(ρ' - ρ) / (ρ' + ρ)}1/2.

The approach to the steady state in gaseous thermal diffusion has been studied using a conventional apparatus consisting of two vessels joined by a connecting tube. The investigation was confined to mixtures of hydrogen and nitrogen. The rate of approach to the steady state was found to be exponential with mixtures of these two gases. It was also found that the rate of approach to the steady state decreased slightly as the percentage of the lighter gas increased. Since the theory shows that the rate of approach to equilibrium is proportional to the coefficient of diffusion D₁₂, this suggests that the coefficient D₁₂ decreases as the percentage of light gas increases. The experimental variation of the coefficient D₁₂ with concentration as determined in this way is compared with that predicted for the elastic sphere type of molecule. The advantages of this method of measuring changes of the coefficient of diffusion with concentration ratio over the ordinary diffusion method are discussed.

Measurements have been made of the refractive index and absorption index of InSb by reflection methods with polarized radiation. Extensive studies of absorption constant have been made by direct transmission measurements.

Both photovoltaic and photoconductive effects have been observed in InSb. At room temperature the photosensitivity extends to approximately 7.5μ, a considerably longer wavelength than for any other known material.

Measurements on current limitation in the low-pressure mercury arc are reported and a theory is given which depends on the limit to the ion generation set by the flux of neutral atoms passing from the walls into the plasma. The paper refers to low current discharges, where self-magnetic field effects are negligible.

The data given on the optical properties of InSb are analysed and precise values for the position and temperature dependence of the absorption edge are given.

The variation of the position of the absorption edge with impurity concentration is explained by the very low effective mass of the conduction electrons, which is estimated by three methods to be about 0.03 of the free electron mass.

The vapour pressure of calcium in the temperature range 800°κ-920°κ has been measured by the Knudsen effusion method. Calcium metal was heated in a specially designed nickel crucible, and the vapour which effused through a narrow slit aperture into a well-defined solid angle was condensed and determined chemically. The vapour pressure P in mm Hg was found to be related to the absolute temperature T by the relation log₁₀P=9.59-10089/T.

Further determinations of the vapour pressure of solid calcium have been carried out by a similar application of the Knudsen effusion method to that described in the companion paper by Douglas, but with radiochemical analysis of the condensed deposits. It is concluded from the good agreement with the results of Douglas and of Pilling that vapour pressure data for the temperature range 800°K to 900°K are now well established, and that the results of Rudberg are in error. The matching of the results with those of Hartmann and Schneider for liquid calcium when extrapolation is made to the melting point is discussed. Agreement in this respect remains incomplete.

Corrections to 1954 Proc. Phys. Soc. B 67 677.