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144. Thermal expansion of solids at low temperatures
MISCELLANEOUS SUBJECTS
S 181
142. Viscosity of Fluid A r g o n under Conditions of Constant Density. ROBERTA SCOTT. D e p a r t m e n t of Physics, Queen Mary College, University of London., England. The falling plug method has been used in measurements of the viscosity of fluid argon under conditions of essentially constant volume over a range of temperatures and pressures. This method of viscometry has been investigated, and a criterion for changeover from central to side-of-tube fall has been established. For central fall, a relation has been found between the dimensions of the apparatus, densities of plug and fluid, speed of plug fall, and the viscosity of the fluid medium.
143. Vapour pressure of isotopic liquids. G. BOATO, G. SCOLES and M, E. VALLAURI. Istituto di Fisica dell' UniversitY., Genova, Italy. This work is part of a study concerning the dependence on mass of the thermodynamic properties of simple systems at low temperature, in order to verify the existing theories on the subject. We have started with liquid argon in the temperature range between the triple and the boiling point. Enriched isotopes need not be used, due to the sensitivity and precision of the mass spectrometer which we have built. Tank argon of ordinary purity has been used throughout and found to be most convenient. The ratio of the vapour pressures of 36Ar and 40Ar was found to be 1.0067 4- .0001 at the triple point, with a temperature coefficient of .0002 per degree Kelvin. Measurements on liquid argon in a more extended temperature range and on other simple liquids are in progress.
144. T h e r m a l Expansion of Solids at Low Temperatures. B. F. FIGGINS, EVA HUZAN and G. O. JONES. D e p a r t m e n t of Physics, Queen Mary College, University of London, England. Following recent measurements of the expansivity of aluminium 1) and solid argon 2) at low temperatures, using the X-ray method, new measurements on these substances and on solid krypton will be discussed. The low-temperature X-ray (Debye-Scherrer) method has been improved by introducing the possibility of motion of the specimen. A sensitive optical method has also b~en developed which is capable of giving both absolute and relative measurements of expansivity at low temperatures. 1) Figgins, B. F., Jones, G. O. and Riley, D. P., Phil Mag. 1 (1956) 747. 2) Dobbs, E. R., Figgins, B.F., Jones, G.O., Piereey, D.C. and Riley, D. P., Nature 178 (1956) 483.
143. T h e Velocities of Sound i n Solid A r g o n . E. R. DOBBS and A. G. BETJEMANN. Queen Mary College, London, England. The ultrasonic interferometer of B a r k e r and D o b b s 1) has been improved and adapted for measurements on solidified gases at liquid hydrogen temperatures. This apparatus will be described and recent measurements of the velocities of sound in solid argon will be discussed.
S 181
142. Viscosity of Fluid A r g o n under Conditions of Constant Density. ROBERTA SCOTT. D e p a r t m e n t of Physics, Queen Mary College, University of London., England. The falling plug method has been used in measurements of the viscosity of fluid argon under conditions of essentially constant volume over a range of temperatures and pressures. This method of viscometry has been investigated, and a criterion for changeover from central to side-of-tube fall has been established. For central fall, a relation has been found between the dimensions of the apparatus, densities of plug and fluid, speed of plug fall, and the viscosity of the fluid medium.
143. Vapour pressure of isotopic liquids. G. BOATO, G. SCOLES and M, E. VALLAURI. Istituto di Fisica dell' UniversitY., Genova, Italy. This work is part of a study concerning the dependence on mass of the thermodynamic properties of simple systems at low temperature, in order to verify the existing theories on the subject. We have started with liquid argon in the temperature range between the triple and the boiling point. Enriched isotopes need not be used, due to the sensitivity and precision of the mass spectrometer which we have built. Tank argon of ordinary purity has been used throughout and found to be most convenient. The ratio of the vapour pressures of 36Ar and 40Ar was found to be 1.0067 4- .0001 at the triple point, with a temperature coefficient of .0002 per degree Kelvin. Measurements on liquid argon in a more extended temperature range and on other simple liquids are in progress.
144. T h e r m a l Expansion of Solids at Low Temperatures. B. F. FIGGINS, EVA HUZAN and G. O. JONES. D e p a r t m e n t of Physics, Queen Mary College, University of London, England. Following recent measurements of the expansivity of aluminium 1) and solid argon 2) at low temperatures, using the X-ray method, new measurements on these substances and on solid krypton will be discussed. The low-temperature X-ray (Debye-Scherrer) method has been improved by introducing the possibility of motion of the specimen. A sensitive optical method has also b~en developed which is capable of giving both absolute and relative measurements of expansivity at low temperatures. 1) Figgins, B. F., Jones, G. O. and Riley, D. P., Phil Mag. 1 (1956) 747. 2) Dobbs, E. R., Figgins, B.F., Jones, G.O., Piereey, D.C. and Riley, D. P., Nature 178 (1956) 483.
143. T h e Velocities of Sound i n Solid A r g o n . E. R. DOBBS and A. G. BETJEMANN. Queen Mary College, London, England. The ultrasonic interferometer of B a r k e r and D o b b s 1) has been improved and adapted for measurements on solidified gases at liquid hydrogen temperatures. This apparatus will be described and recent measurements of the velocities of sound in solid argon will be discussed.