The construction of an all-glass apparatus for measuring the rate of thermal decomposition of oil-ejector pump oils and the results of the experiments about three varieties of oil, i, e. dibutylphthalate, mineral oil and alkylnaphthalene, are described.
(1) The thermal decomposition is a first-order reaction and the rate of evolution of produced gases is proportional to the oil quantities.
(2) There are no effects on the decomposition reaction when either of four metal plates, that is iron, copper, brass and aluminum, is put in to the boiler.
(3) The thermal decomposition of the oil-ejector pump oils is similar to that of the diffusion pump oils in several points; the activation energies and the decreasing behaviors of the rate in the first period, etc.
(4) The rate of the thermal decomposition of dibutylphthalate, mineral oil and alkylnaphthalene are 5.8 ×10^-4, 2.6× 10^-4 and 1.7 × 10^-4 Hg.1/sec.g. respectively at 210°C and their activation energies are 29, 26 and 18 Kcal/mol respectively.

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Influences of the various pumping fluids on the operating performance of 8″ ejector booster type vacuum pump are examined.
The fluids used are diethylphthalate, dibutylphthalate and hydrocarbon oil (mean molecular weight=250). Another combined factors, i. e. diameter of throttle, heat input, foreside pressure are also changed together.
The authors have gotten some effective informations with these three pumping fluids about the relations between evacuating speed and heat input, boiler pressure and heat input, boiler temperature and heat input respectively.

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The discharge characteristics of cold cathode ionization gauges having a central wire electrode, were compared with those of the ordinary types of Philips gauge. As is stated ordinarily, two types of these gauges behaved similarly in the lower vacuum region.
At the high vacuum, however, it has been observed that the discharge characteristics of the former type are different from the latter. The stability of the gauge was somewhat improved by using the central wire electrode.

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The kinetics of the initial fast adsorption of carbon monoxide and hydrogen on evaporated nickel films has been investigated by a flow method. The ultimate vacuum obtained is 1×10^-9 mmHg and the surface of the film can be kept clean during and after evaporation. There are two distinct differences in the rate of chemisorption between carbon monoxide and hydrogen. The sticking probability of carbon monoxide is estimated to be nearly 1 at 0°C on clean surface and remains constant until the surface is covered to some extent. With hydrogen, however, it is about 0.1 at the same condition, and begins to decrease at a lower coverage.
Applying the potential energy diagram proposed by Lennard-Jones to the above systems, the difference in the initial value of sticking probability is explained as due to the difference in type of chemisorption, i.e., carbon monoxide chemisorbs without dissociation, whereas hydrogen does with dissociation. The difference in the decrease of sticking probability with adsorption is considered to be due to the difference in mobility of adsorbate on the surface ; at room temperature surface migration is easy for hydrogen, but not for carbon monoxide. The chemisorption model proposed here can be extended to the slow adsorption of carbon monoxide previously reported.

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Evacuating speed of a rotary vacuum pump decreases as pressure decrease, but mathematical expression showing this tendency is unknown. Only the equation dP/dt=-So/V (P-P_min) is introduced by experiences, but the physical meaning of P_min (final pressure) is very chaotic.
The author explains this meaning by simple calculation, as P_min is the parameter containing dead space volume, outgassing and leakage.
But unfortunately, as the above equation is not always appropriate for the actual pumps, the author proposes more adequate expression S = {1- (P_min/P)^a} So.

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