The dihedral angle of an alcohol lens at the air/water interface and the three kinds of interfacial tensions of air/1-octanol/water and air/1-decanol/water systems have been measured as a function of temperature from 288.15 to 313.15 K at 2.5 K intervals under atmospheric pressure. In order to measure a dihedral angle, the new experimental apparatus was constructed and the new procedure was adopted. By comparing the dihedral angles measured with those calculated by applying Neumann's relations to the interfacial tension values, it was concluded that the dihedral angle measurement was performed with a satisfactory accuracy. The properties of the interfacial film and also the occurrence of the intruding of water phase on the air/alcohol interface were discussed.

The dihedral angle of an alcohol lens floating on the air/water interface and the three kinds of interfacial tensions of air/1-undecanol/water and air/1-dodecanol/water systems were measured as a function of temperature under atmospheric pressure. By applying the thermodynamics of interfaces to the experimental results of the interfacial tension measurement, it was found that the phase transitions between the expanded and the condensed states take place in the interfaces. It was found that there are break points on the dihedral angle versus temperature curves corresponding to the phase transitions of the interfacial films. The mutual relation among the states and the phase transition of the interfacial film, the wetting behavior, and the intruding phenomenon of the water phase on the air/alcohol interface was discussed. It was shown that the dihedral angles measured coincide with those calculated by Neumann's equation with a satisfactory accuracy except at very low temperatures. The discrepancy at the low temperatures was proved to be attributable to the meniscus of the air/water interface.

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Hardness and electrochemical polarization characteristics of Al-Zn-Mg alloys containing up to 0.1 at% of Cu, Cr, Si and Ti were investigated. The Vicker's hardness of the alloys aged at 180°C did not change remarkably by the addition of these contents up to 0.1 at%. Pitting potential of the alloys in 0.5N NaCI solution changes into noble value with increase in Cu and/or Cr contents. Passivation current density of the alloys reduces with increase in Cu, Cr and Ti contents. Pitting potential changes into noble value and passivation current density reduces with increasing aging time.These phenomena correspond to the change of solute quantity of Zn and/or Mg in the surface layer of the alloy materials.

The effects of Be and Na on the aging phenomena of AI-Si-Mg alloys were investigated mainly by means of resistivity measurement in liquid nitrogen and by electron microscopy. Experiments were conducted to investigate the effects of addition of Be (0.09 wt%) and Na (0.009 N 0.01 wt%) on the formation of G. P, zones in AI-Si--Mg alloys.The results obtained were as follows :(1) The density of distribution of the G. P. zones composed of Si and Mg atoms increased when Be was contained in the G.P. zones. When these alloys containing Be were aged at high temperatures, the alloys were prevented from over-aging by the effect of Be.(2) The addition of Na to Al-Si-Mg alloys prevented them from aging.(3) The structural changes during age hardening were investigated by X-ray diffraetiometry and electron microscopy. It was found that the precipitate formed was the intermediate phase (9') in aging at low temperatures (up to 300°C); but the equilibrium phase Mg2Si (fJ) was formed together with fl'-phase in aging at above 300°C. (Received Dec. 20, 1971) Faculty of Engineering, Nagoya University (Nagoya)