Considerations should be given to the properties of hydraulic brake fluids which are being used at present for almost all vehicles in regard to the corrosiveness to metals, effect on rubber, boiling point, pour point, volatility etc. ... Results of experiment on swelling of rubber cup by blenders of the fluid such as n-butanol and diacetone alcohol and the experi-mental arrangement are shown. The rate of swelling is measured in the fluid to, produce the working condition in practice instead of taking the cup out of the fluid every time the measurement is made which is the method designated by the SAE standards.
The principle of Scott's method of using triode valve for Pirani gauge and the results of experiment are described. Pressures down to 1x10-5mmHg are measured favourably and conveniently with the method.
The electron emission and the life of the triple oxide cathodes were measured by varying the composition of the oxides. The maximum d. c. emission is obtained from the composition BaO:SrO:CaO=4:6:0 to 5:4:1. Under the pulse condition the optimum composition is 4:5:1 to 5:4:1. The emission in the optimum composition range is stable and has long life time. The particle form of the co-precipitated alkaine-earth carbonates was observed by optical and electron microscopes. The results also indicate that the emission will be independent of the size of carbonate particles.
The change of thermionic emission patterns from oxide-coated cathode was by Johnson-Schockley type emission microscope. It is the general characteristics that the oxide-coated cathode is activated after the electron bombardment. It will be possible to suppose that barium oxide dissociates into barium atoms and oxygen molecules by electron bombardment, and thus layers of excess barium atoms are formed on the oxide-coated cathode, whereas the oxygen molecules formed may de liberated from the surface. Barium atoms thus pro-duced on the oxide-coated cathode surface, at a comparatively higher temperature or electric field, can diffuse easily into barium oxide cathode and compose the impurity centre gradually. It is also found that the dissociation probability changes with the activation degree of barium oxide and has a structure sensitive character.
Characteristics of tubes with titanium anode are compared with those with nickel anode for triodes and pentodes. Decay of emission is very little owing probably to almost no occlusion of injurious gas in titanium. Space charge characteristics such as mutual conduc-tance and anode current are found to increase considerably with time. This is reasonably ascribed to the deposition of barium atoms onto control grid of the tube. If the extreme dissociation of deposited barium oxide on the titanium anode by electron bombardment can be arrested, titanium will be a very good material for anode.