The tensile strength of sintered iron is improved by steam treatment. Some experiments were conducted for explaining the effect.
Tensile tests were conducted on two kinds of different powders, reduced and electrolytic ones, to investigate the effects of tests on their properties. However, no effects were given by the tests.
On the other hand, the change in internal porosity was observed by microscopy.
These experiments and observations showed that the improvement in tensile strength would be due to the following three effects:
1) Effect of impregnation
2) Decrease in notch effect
3) Decrease in density of skeleton
A model of pores was prepared by determination of the rate of impregnation effect. The above three effects were explained by a schematic graph given by the model.

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The following experimental results were obtained by chemical analysis, DTA, TGA, X-ray diffractiometry, using infrared spectrometer, etc.
(1) The hydrated chromium oxide film electrolytically formed on cathode from aqueous solution of single chromic acid was composed of chromium hydroxide with chromic anhydride adsorbed thereon.
(2) The water content on chromium hydroxide in hydrated chromium oxide film was 33.5% and content of chromium anhydride adsorbed on the film was 16.5%
(3) The approximate structural formula of the hydrated chromium oxide film was as follows:
(CrO₃)(Cr₂O₃)₂⋅10H₂O

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The previous paper described that the proceeding of dyestuff adsorption was not satisfactory by the blending of various kinds of ions in the dye bath. In particular, the effect was greater by blending of organic acids.
This paper describes the elimination of obstructive ions in the bath with ion exchange resins. It was found that sulfate, oxalate, acetate, and citrate ions were easily removed; however, when aluminum ions were blended in the bath, a large quantity of dyestuffs were adsorbed on aluminum hydroxide.
In order to eliminate the effect, the precipitation of aluminum hydroxide was prevented by the addition of EDTA or sulfosalicylic acid in the amount corresponding to the aluminum concentration.

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Reliability in soldering of multi-layer printed circuits depends upon solderability of the surface to be joined. Solderability of coatings on lead wires and copper foils was determined by minimum wetting-time test, spread-area test, Passel's contact angle test, and the rate of wetting in dip test.
Most of freshly prepared coatings exhibited high solderability. However, in practical, many assemblies are troubled by faulty soldering owing to poor solderability of coatings after storage.
Therefore, the soldering test after accelerated ageing was required for estimating the solderability after storage.
There was much dispersion in the results of soldering tests, which interrupted reproducibility. However, the soldering test afer accelerated ageing led to an accurate evaluation of solderability. Moreover the cause of solderability loss during storage was deduced from the accelerated ageing test.
The following conclusions were drawn by the tests:
(1) The coating of the highest solderability was electrodeposited tin-lead alloy, and the second was electrodeposited tin. Electrodeposited gold coating, which had ever been assumed to have high solderability, was not so excellent and especially at low temperatures.
(2) Poor solderability resulted from the following defects of deposited coatings:
(a) Organic and inorganic surface contaminations which were derived from additives in the plating bath.
(b) Porous surface having a large surface area.
(c) Pinholes and other defectives being produced under bad plating conditions.

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