The coagulation reaction of chromium ion was investigated by means of distribution curves of chromium (III) aquacomplexes in Cr₂(SO₄)₃ solution and titration curves, solubility curves, and sedimentation volume in binary systems such as Cr³⁺-Fe³⁺, Cr³⁺-Fe²⁺, Cr³⁺-Cu²⁺, Cr³⁺-Zn²⁺, and Cr³⁺-Ni²⁺. The chromium ion was found to form aquacomplexes having positive or negative charge in aqueous solution by means of ion-exchange method. The positively charged aquacomplexes in the solution amounted to 70% of total complexes before titration with an alkali; but they decreased to 50% in the pH range for precipitation. Therefore, it would mainly be positively charged aquacomplexes which were precipitated in the earlier stage of coagulation reaction. In binary systems of Cr³⁺-Fe³⁺ and Cr³⁺-Cu²⁺ systems, the aspect of precipitation of each ion was distinguishable in the titration curves and solubility curves; but in Cr³⁺-Fe²⁺, Cr³⁺-Zn²⁺, and Cr³⁺-Ni²⁺ systems, the forms or those curves were nearly identical with those in chromium solution. Furthermore, as the results of sedimentation volume, the precipitate of Cr³⁺-Cu²⁺ system was considered to be nearly the mixture of individual precipitates, but the precipitate of Cr³⁺-Zn²⁺ system was not considered to be the mixture. Therefore, in binary systems, Fe²⁺, Zn²⁺, and Ni²⁺ would co-precipitate with chromium ion, but the co-precipitation of Fe³⁺ and Cu²⁺ with chromium ion would be very little.

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The lattice constant of nickel electrodeposited from Ni(CF₃COO)₂-halide-MeOH solution was 3.50-3.56Å. A strong [111] grain orientation was observed in the nickel deposits. The grain size of the nickel deposits was 52-173Å. When ammonium halide was added to Ni(CF₃COO)₂-MeOH solution, the grain size of the nickel deposits increased. The grain size of the nickel deposits obtained from the solution containing NH₄Cl was larger than that of the deposits obtained from the solution containing NH₄Br.

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Diffusion couples of Fe-Ni, which mean electrodeposited nickel on electrolytic iron, were studied. This paper discribes the effects of temperature and duration for heat treatment on composition, structure, hardness, etc. of diffusion layers formed. The results were summarized as follows. The diffusion layers were formed at low heat treatment temperature such as 600°C. It was shown that the nickel concentration is about 25-30wt% in diffusion layers at each treatment temperatures. Diffusion layers showed volume diffusion process in the heat treatment temperature range between 600-800°C, but it was shown grain boundary diffusion process in the temperature range between 900-1000°C. The results of hardness measurement indicated that the layer formed at lower than 800°C having a maximum value Hk=270 and at high temperature than 800°C having low value hardness such as Hk=120.

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Diffusion couples of Ni-Cr, which mean electrodeposited chromium on electrolytic Nickel, were studied. This paper describes the effect of temperature and duration for heat treatment on composition, stracture, hardness, etc. of the diffusion layer formed. The results were summarized as follows. These diffusion layers has already reached measurable at 600°C. It was showed that the nickel concentration was about 72% in diffusion layers at each heat treatment temperature. Diftusion layer showed grainboundary diffusion in the temperature range between 600-1000°C. The X-ray diffraction paterns and X.M.A. analysis revealed that the diffusion layer was a Ni rich solid solution. The results of hardness measuraments showed that the layer formed at low temperature was having hardness as Hk=350, and at high temperature was hardness as Hk=150.

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