Film resistance of metal surfaces can be measured as a very high value if coherer action and breakdown of the film are avoided. The author previously reported the apparatus and this time a simple recorder of direct current type is described.
Film resistance of parkerised steel surfaces is recorded. It is found that the ordinary parkerised surfaces have very high film resistance with local defects.

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As mechanical polishing of aluminium and its alloys is very difficult for their mildness, chemical and electro polishing are widely adopted for these metals, and various compositions of electropolishing bath, acidic or alkaline, for amphoteric aluminium have been suggested. But these baths are effective only for pure aluminium but not for alloys. The author, therefore, investigated electropolishing of various aluminium alloys. In this paper, the result of electropolishing in phosphoric acid-chromic acid bath which he proposes for carbon steels and copper alloys is reported.
(1) In phosphoric acid-chromic acid bath at comparatively low bath voltage-current density, electropolishing effects on aluminium alloys are good.
(2) Addition of chromic acid to the bath is effective to make oxydation or passivation of anode uniform, to prevent selective dissolution of added alloying elements and different structure of alloys, and to get smooth surface with luster. Silmin is well polished, silicon contained in it being oxidized and dissolved as colloidal silica.
(3) Electropolishing of cast material in the bath shows little effect but becomes a little effective after heat treatment such as quenching or annealing.

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Mechanical polishing of stainless steels is difficult and handling skill is required, for they are apt to be overheated locally due to their low heat conductivity. Electropolishing, therefore, has long been adopted for stainless steels. As it has especially good effect on 18-8 type stainless steel, various composition of electropolishing bath have been suggested.
In this paper, the result of electropolishing of 18-8 type stainless steel and 13% chromium steel in phosphoric acid-chromic acid bath which the author proposes for carbon steels, copper alloys and aluminium alloys, is reported.
(1) Phosphoric acid-chromic acid bath showed good effect on 18-8 type stainless steel and 13% chromium steel.
(2) The addition of chromic acid to the electropolishing bath promoted the oxydation of anode and prevented selective dissolution of chromium contained in the steel.
(3) High anode current density causes to produce streaks by oxygen bubbles which is generated on the surface of anode, while low anode current density and long time treating improves the polishing effects.
(4) In spite of heat treatments, 18-8 type stainless steel always consists of austenite crystal stracture, but as its grain size becomes smaller and strain is removed more completely by heat treatment, the electropolishing effect is better. Polishing effect of 13% chromium steel is influenced by the heat treatment. It is best for that of quenched martensite structure and better for that of solbite structure.

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Continued from the previous paper, the frictional behaviour of some of the compounds for barrel finishing is examined by the four-ball apparatus using a stone ball for the top rotor.
Results are somewhat different from those using steel balls. With compounds for cutting, the coefficient of friction is higher according to the cutting action of abrasives With compounds for finishing, the coefficient of friction is practically equal according to the lubricating effect of the compounds and lubrication breaks down at a higher pressure.

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Complex salt of cupper and zinc cyanide is decomposed into CuO and ZnO, by H₂O₂, and then dissolved by HNO₃.
The total amount of Cu and Zn can be determined by titrating the solution with EDTA with PAN (α-Pyridyl-β-azonaphtol) as indicator.
Zn can be titrated directly by EDTA in the presence of Cu which is masked by the addition of slight excess of thiosulfate at pH 5-6, using the PAN indicator and methanol.
The amount of Cu in the mixture can be calculated by the difference of the above two.

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The fundamental study of the levelling action of the acetylenic addition agents was made by measuring the cathode potential during electrolysis and the levelling power defined as a proportion of the deposit thickness obtained at the edges and the recesses of the notches (60°, 90°, 120° and 150°).
The addition agents used were propargyl alcohol, butyne-1, 4-diol, methyl butynol, methyl pentynol and dimethyl hexynediol. The results obtained were as follows:
(i) When the acetylenic addition agents were added, the increase in the cathode potential toward the negative side was observed, especially with the agitation of the electrolytic solution. There were some differences in the increasing trend of the cathode potential among them. Propargyl alcohol, methyl butynol and methyl pentynol gave the most remarkable increase in the cathode potential, butyne-1, 4-diol intermediate and dimethyl hexynediol lesser extent. In all cases the more the addition agents, the more increased the cathode potential.
(ii) The narrower the angles of the recesses, the better the levelling power. There existed some relationship between the levelling power and the increase of the cathode potential, that is, the more increased the cathode potential, the better the levelling power was. It is suitable to use so much amount of the addition agent as to increases the cathode potential toward the negative side within the range of 30-60mV.

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The suppressive actions of the addition agents for nickel plating on a polarographic maximum were applied to their analysis. The copper maximum was found to be suitable for the analysis of the brighteners of the first class. The addition agents used were 1, 5 naphthalene disulfonate, 1, 3, 6 naphthalene trisulfonate, P-toluene sulfonamide, benzene sulfonate, 1 naphthalene sulfonate and saccharin.
According to G.Semerano, the following empirical equation was proposed;
log I⁰_a/I_a=C_sS+K_s
where I⁰_a was the adsorption current (maximal current minus the limiting current of the wave) in the absence of a suppressor, I_a that in the presence of a suppressor, C_s the concentration of the maximum suppressor, S the specific suppression coefficient, and K_s the constant which was different for each suppressor. All the brighteners of the first class gave the results in fair agreement with this equation, being able to be analyzed by the method using the suppressive action of them.

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