The mechanism of tungsten solution in plating was investigated and the following results were obtained.
1) Tungsten acid precipitates neither in the neutral solution, nor in the weak acid or organic acid solution.
2) In the electrolysis of the weak acid or organic acid solution, the electric resistance gradually increases and the solution around cathode turns blue. Thus the poly-tungsten acid is formed at the cathode by reduction.
3) In the electrolysis of the neutral solution, too, the electric resistance increases a little, but not so much as in the case of the acid solution.
4) In the electrolysis of the alkaline solution the electric resistance decreases little by little and after the lapse of certain hours becomes almost constant. The decreasing ratio of the electric resistance is inversely propotional to the alkaline content.
5) In the electrolysis of the alkaline solution, it is supposed that the composition of the sodium tungsten acid is changed to Na₂[WO₂(OH)₄] which dissociates in the solution forming WO₂²⁺ ions.
6) In the tungsten plating, it is supposed that the WO₂²⁺ ions thus formed are deposited at the cathode and reduced at the same time to the metallic state by the hydrogen generated.

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New analytical method of naphtalene disodium sulfonate as a brightener for bright nickel plating was studied. This spectrophotometric method is one of the colorimetric analysis using light of appropriate wave length (λ=285mμ), therefore, it is not necessary to consider the effect of other constituents in the bath. In addition, it was proved that this procedure was a simple and rapid one which is usuable for other brighteners such as carbocyclic compounds. Applying this method, the consumption of the brightener with electrolysis was measured.

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The authors investigated the behavior of the paint film of zincchromate or mellamin paints on the single crystals or coarse grains of aluminum, when the slip deformation of aluminum occurred by stretch.
The results were as follows:
On the thin film of paint, the microcrack was found when the tensile strain became 3 percents, and on the film of zincchromate and hard mellamin paint breaks occurred along the slip lines which were inclined 75 degrees or more to the tensile direction.
On the thick film, the crack was not found until deformation of 5 percents and on the film of zincchromate breaks occurred in the direction of the resultant of slip and tensile directions.
On the mellamin film breaks occurred perpendicularly to the tensile direction.
In the case of soft mellamin paint, the film was defermed along the slip deformation of aluminum until 12-15 percents and breaks occurred perpendicularly to the tensile direction.

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Nitriding of steel is an excellent method having many advantageous features, but it has a great defect to take a long time.
In this study the author performed the rapid nitriding method with molten salt. First, the nature of nitriding bath was theoretically inspected, many preliminary experiments were done, and the reasonable nitriding salt bath and the condition of its treatment were investigated.
The principal composition of the salt bath was NaCNO, and to this are added neutral salt and basic salt for the purpose of stabilized bath and the suitable melting point for treating temperature was obtained.
For the experimental specimen, 13-Cr steel, 18-8 stainless steel, case hardened Cr-Mo and standard nitriding steel were used. Their hardness was high, the grade being Hv 1000-1200, except Cr-Mo case hardening steel, and great difference in hardeness was not observed in the nitriding layer, treated for over 2 hours at 510°C. Moreover, the backward test of the salt bath, was carried out examineing the stabilization of the salt in use. From the result, it can be said that their nitriding hardness is very stable as of industrial utility.
By this study, it is clarified that the salt bath performs sufficiently the primary role of the rapid nitriding method.
In comparison with the old gas nitriding method with NH₃, the cause of promotion in the nitriding was also investigated.
It is considered that there are many factors, but the main reasons for good nitriding are two; one is the rich existence of nascent N° in the bath at treating temperature, and the other is the pressure inflicted by the viscosity of salt on the surface of treated steel in the salt bath.
So, it may be concluded that the rapid nitriding by salt can be done at the same treating temperature as that of nitriding by gas.

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