This report deals with the studies on settle gelatine drop method to evaluate the preventability of soft film type rust preventive oils. This evaluation method is recognized to be more useful than the ordinary settle water drop method studied by Baker et al., because of its better procedure and statistical consideration in analyses of test results. The test specimen is a plate having 75mm×55mm×3mm in its magnitude, and 20 drops of each 0.05cc gelatine in which potassium ferricyanide and phenolphthalein were resolved, are settled on its oil coated side. After one or two hours the green anode specks appear in drops at rondom, but if the oil is very preventive a anode specks are very few. Distribution of rust specks, appeared at rondom in each drops, follows Pólya-Eggenberger's distribution, and the rust drop numbers in 20 drops follows a distribution as attribute values. These values are used in each factorial experiments by the adequate transformations of the attributes, and known useful as numeration of rust preventability of test oils.

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Some effective inhibitors against chemical (or natural) corrosion phenomenon, not induced by the underground stray current were investigated. Terrible corrosion is often seen on the cables dipped in the water of manhole. Therefore, the corrosion inhibitions of such reagents added into manhole water as ammonium-sulfate, sodium-sulfate, sodium silicate, sodium-hexame-taphosphate, α-picoline and aliphatic-amine were examined. For the purpose of accelerating the corrosion rate of lead, electrolysis and galvanic action by the contact of other metal or material were applied, and the corrosion potentials of the test pieces were measured in the same water.
1) The best effective corrosion inhibition was observed in the cases of addition of ammonium-sulfate or sodium-sulfate. Other reagents above mentioned were less effective, because they could not resist the local corrosion such as “pitting”, although they seemed to reduce total weight loss of the test piece.
2) The corrosion inhibition of ammonium-sulfate was found in the cathodic as well as anodic corrosion.
3) The contact of more electronegative metal or nonconducting material as glass on the corroded surface was usefull for the auxiliary test to evaluate effectiveness of inhibitors. This method of corrosion test seems to be useful practcally.

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Microscopical rust speck calculation methods to evaluate the preventability of rust preventive oils were studied.
Two methods, the ordinary method of calculating the mean rust specks of several microscopical fields of standardized magnification and a new method of calculating the specks observed only at the cross section points of inclusion lens of microscope disregarding the specks out of the cross section points, were studied and compared.
Because of the speck distribution type and the labor of counting, the former is recognized useful in the case of a few specks and the latter in the case of many specks.

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Various workers have reported the effects of ultrasonic waves on the electro-deposition of metal. In this paper, the effect of ultrasonic irradiation on bright nickel plating in watt type bath, as shown table 1., and particulary the effect of the frequency and intensity of ultrasonic waves were studied. For this purpose, two sorts of generator which have frequency of 20kc. and 450kc, were used, and the measurement of accoustic pressure, instead of the intensity, were observed before the experiment was begun. The ultrasonic weves ware irradiated striking parallel to the specimen surface as shown in fig. 2..
The following results concerning charactaristics of the deposite were obtained.
1. It was seemed that no changes of the decomposition potential was observed as compare to the ordinary plating.
2. The cathodic current efficiency with the use of high frequency was slightly higher than the efficiency with the use of low, but details of them were not clearly. However, the use of ultrasonics rised the upper limit of the effective current density.
3. Pinholes at the electro-deposition was certainly less with the use of low frequency, especially, it was remarkable at high current density.
4. The higher intensity brought out the larger hardness of the deposite in the range of considerablly high intensity side. This large hardness was considered as the effect of certain work due to alternating changes of pressure caused by ultrasonic wave motion.
5. An excellent brightness was observed with the use of low frequency, but, some times, the stripes pattern caused by standing wave appeared with the use of high frequency.
6. Generally, the effect of combination of ultrasonic irradiation and mechanical stirring was superposed the each good charactaristics of the two respectively.
From the above, we can say that the precision measurement of intensity in the plating bath and intensites which variate in wider range especially lower side are neccessery. These two are important on the dractical utilization to cut down the initial cost of the instrument. Effect on the changing of the direction of ultrasonic irradiation to specimens, hydrogen brittleness, throwing power, and leveling power will be studied as next work.

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