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Measurements of the x-ray-induced expansion of KG and NaCl have been carried out with a capacitive dilatometer at temperatures near 20°K. The expansion of KC1 was found to be more than an order of magnitude greater than that of NaCl. Greater probability of nonradiative electron-hole recombination in KC1 is suggested as the principal cause of the disparity.

Values of the viscosity of the normal component of liquid helium II have been determined using the rotating cylinder (Couette type) viscometer. Primary attention has been given to the temperature range between 0.79° K and 1.1° K; values at higher temperatures have been determined to provide a check on previous determinations. The results over the whole temperature range are closely fitted by an equation of the form given by Khalatnikov (Uspekhi Fiz. Nauk, 59, 673 (1956)).

Measurements have been made of the coefficient of linear thermal expansion, α, of Cu, Ag, Au, Al, α-Fe, and Ni at temperatures below 100 °K using an interferometric method in which the spacer between the optical flats of a Fabry–Perot-type interferometer was made of the material studied. The lowest temperatures at which values of α are given are about 20 °K (Cu, Ag), 11 °K (Au), 25 °K (Al, Fe), and 32 °K (Ni). The results are discussed in terms of the Gruneisen parameter γ which, for Cu, Ag, and Au, is approximately constant at high temperatures, but tends to rise slightly as the temperature is reduced towards the lowest temperatures of measurement. For Al, a correction for the electronic contribution is applied below 40 °K to deduce the lattice contribution γL, which rises more spectacularly at low temperatures than the results for the noble metals. For Fe, separation of α into two contributions, one from the lattice and one from the combined magnetic and electronic effects, may be made, giving γL = 1.45; the combined magnetic and electronic contribution is very small.

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