Aconsiderable amount of work has been done in connection with the diffusion of one metal in solid metals. Relatively little, however, is known on the rates of diffusion of two metals in solid metals. In the 1 st § the rates of individual diffusion of Ni, Sn, Ag, Zn, Si and Sb, respectively, in solid copper were determined, and, in the 2 nd § the rates of simultaneous diffusiton of Ni with Sn, Ag with Zn and Si with Sb, respectively, in solid copper were evaluated; in the 4 th § the microstructures of these specimens after diffusionannealing were observed. Concentratio_??_distance curves were determined by analyzing layers cut successively from cylindrical specimens of copperplating alloy bars containing about 5 atom percent solute and causing interdiffusion to take place between the alloy and the copper, diffusion constants as a function of solute concentration were caluculated by Matano's method. The results thus obtained are: Except Sn, the solute concentration in binary core alloys were relatively so dilute in comparision with the degree of their solid solubilities in copper that the variations in rates of diffusion with solute concentration can not be so conspicuous. At 800°, diffusion constants of 1. 6_??_1.1×10^-5cm²d^-1 for Ni are markedly smaller than those of 6.8_??_47.4×10^-5cm² d^-1 for Sn; At 750°, 46_??_9.8 for Ag are larger than 2.7_??_4.2 for Zn; At 600°, 2.5_??_7.8 for Si somewhat larger than 1.2_??_6.9 for Sb.
Similarly, rates of simultaneous diffusion of Ni with Sn, Ag with Zn and Si with Sb in copperplated ternary copper core-alloys, containing about 5 and 2.5 atom percent of metal solute respectively, were caluculated. At 800°, the diffusion constants of 3.5_??_6.3×10^-5cm²d^-1 are for Ni and 4_??_32.9×10^-5cm²d^-1 for Sn; at 750°, 4.2_??_4.8 for Ag and 4.1_??_7.7 for Zn; At 600°, 3.6_??_5.6 for Si and 7.7_??_24.4 for Sb. It was found from the results obtained in this reports that the diffusion constants which are larger in individual diffusion have the tendency to decrease in simultaneous diffusion and, on the contrary, those which are smaller in individual diffusion have the tendency to increase in simultaneous diffusion.

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The microstructures of the alloys containing from 6.5 to 10 per cent of aluminium quenched from the β-range were studied in connection with the “heat treatment diagram”, which was suggested from the theory maintained by Profs. K. Iwase and S. Takeuchi. (I) From the results obtained, it was found that the change of the eutectoid transformation depends on the form of the heat treatment diagram. Moreover, these alum inuim-silver alloys proved that the heat treatment diagram can be applied to the case where the eluilibrium diagrams, as shown in Fig. 4, mutually situated face to face.

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In the present experiments on some molton Al alloys, the strength of the diffused layers and their thermal corrosibilities were measured by means of the compression tester and chemical balance. The results are obtained; (1) The niinirnwn diffused layers are obtained in the medium of molton Al-Si alloys, (2) The strength in the diffused layers are mainly effected by thair thickness ratrer than their structures (3) The anti-oxydation films are formed on the surfaces of the specimens by means of the above treatment.

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The cooling stress restored in quenched Ag-Ca alloy is released as the precipitation due to continued aging, the faster the aging temperature elevates. In the case of AI-Cu alloy, the residual stress slightly increased at first up to the period of the formation of the cluster and then gradually decreases up to the precipitation of the θ phase, no sign corresponding to the formation of θ'.

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It was shown by catching the microstructure of cast iron quenched in the process of solidification that the formation process of flake graphite was essentially the same, as fine graphite, although the appearances of these graphites were greatly different. The flake or fine graphite was separated as eutectic from the melt.

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Mill carhurizatiui by such a sappressor as alumian or phosphatesystem was studied. It was found that the suppressor either Al₂O₃ or Ca₃(PO₄)₂ reacted with the promoter BaCO₃ or Na₂CO₃, forming aluminate (BaO•Al₂O₃) or phosphate [Ba₃(PO₁)₂ or Na₃PO₄] at carburzing temperature. The intensity of the promotice power of BaCO₃ for Na₂CO₃ was depressed when used together with a suppresser of alumina or phosphatesystem, because their reaction products had little effect on carburizing. Al or Fe-Al as the suppressor of alumina-system was oxidized in carburizing atmosphare forndng alumina, and then the alumina reactcl with the promoters as above. On the other hand, Al, diffusing into the surface of steel, suppressed carburizing. When bone-black was used in carburization, phosphate in it having been reduced the produced vapour of plusphor diffused into steel. But the phosphor scarcely effected carburizing. Finally, on the stand punt of rate process, mechanism of depression in promotive power of BaCO₃, and Na₂CO₃ by the reacthvi with suppressors was considered.

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As described in the 1 st and 2 nd reports, when the carburizer with any suppressor is used, the promotive power decays according to the reaction between the suppresser and the promoter in the carhurizer. As the result of decaying, the carbon content in the surface layer of carhurized steel lowers with the proceeding of carburizing. It was calculated nn the stand point of Jaw of diffusion by applying the Duhamel theory in thermal conduction, how much this lowering offected the carbon distribution in carburized case, and found that the carbon distribution was not steeper and scarcely distinguished from that treated with the common mild-carburizer.

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One of the present authors reported a protective method about ten years ago in which specimens of aluminium and duralumin were treated first at 100° with a mixed aqueous solution of CaO, CaSO₄ and a small amount of ZnO and then with an aqueous solution of Na₂SiO₃. In the modified method the specimens were treated at 60° for 2_??_3 minutes with 2% NaOH solution and then with a mixed aqueous solution containing CaO, CaSO₄, K₂Cr₂O₇, KNO₃, Na₂SiO₃ and a small amount of KMnO₄ for 20_??_30 minutes.
One of the electrolytic process was also attempted in which the, specimens were pretreated for 30 seconis by 2_??_3% NaOH solution at room temperature and then with the electrodes in 25% H₂SO₄ solution; A. C. being applied for 5_??_60 minutes. The effectivencso of the protective films prepared by means of the above processer against. corrosion by 3% NaCI solution was compared.

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Tellurium is precipitated quantitatively with sulphur dioxide from the solution of 2 N hydrochloric acid containing 5ml of sulphuric acid in which the total volume is 100ml and is not precipitated if the concentration of hydrochloric acid exceeds 9 N. Selenium is precipitated quantitatively in the same condition as tellurium if the concentration of hydrochloric acid exceeds 4 N. Therefore the separation of selenium and tellurium is possible in the presence of sulphuric acid when selenium is precipitated in a concentration more than 9 N of hydrochloric acid and tellurium is precipitated from the filtrate after dilution of filtrate to 2 N of hydrochloric acid.

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