Following to the theory of invar, previously proposed by the present investigator, he has measured the thermal expansion of ternary alloys of cobalt, iron and chromium, and has found that an addition of a small quantity of chromium to cobalt-iron alloys containing more than 50 per cent of cobalt considerably reduces their expansibility. The measurement of the thermal expansion of alloys having small expansibility was made from the temperature of liquid air to the vicinity of the magnetic transformation point, and the range of temperature available for this small expansibility was examined. The smallest coefficient of linear expansion at 20° found in the present investigation was -1.2×10^-6. Further, it was found that alloys having small expansibility were practically incorrodible in dilute solution of NaCl. Some physical properties of these alloys were also determined.

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The diagram of this system has since 1927 been studied by the author and his collaboratars and the results of the work of five papers have been published in the Kinzoku no Kenkyu and the Nippon Kinzoku Gakkai-Si. The present paper is the final summary of the author's work.
Since there exist diverse opinions among the workers on the equilibrium relations of the Cu-Sn system, the author with his collaborators established the true equilibrium relations at least in its general trend. The minute detail such as the precise determination of α/α+β and α/α+δSphase boundaries by drastic annealing as has done by Owen and Williams, is left for the further research.
In this series of investigation all the methods avairable in the present state of physical metallurgy were used among which may be cited, the common thermal analysis, the differential thermal analysis, a special and more precise differential thermal analysis, the temperature-electric resistance measurement, the temperature dilatation measurement, the microscopic examination and finally the X-ray research at high temperatures.
From the data obtained by these methods of investigation the author established the equilibrium relations of the Cu-Sn system as shown in Fig. 26. There are two new points in this diagram, that is, the introduction of _??_ phase given by the present author and the eutectoid transformation δ_??_α+η at 325° given by Owen and Williams, The other relations are those which have been frequently discussed by many workers and they are not new. Each lines, however drawn in the present diagram is based on the positive proof excluding any speculations or inductive process of reasoning frequently made in the absence of firm basis. The author hopes that his diagrams shall gain an appreciation and that no vain effort shall be made further on the same subject.

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This paper contains the results of experiments on the corrosion of copper alloys when immersed in 30% HCl at room temperature and in 20% HCl on boiling condition-the copper containing various amounts of Cd, Sb, P, Ag, Si, Al, Mn and Zn. The resistivity of many copper alloys and nickel-copper alloys selected from the data of the above experiments as well as of some famous copper alloys, in acid were also studied. According to these experiments, it is confirmed that the resistivity of copper against 30% HCl is increased by a small addition of Si, Sb, Zn or some amount of Mn, and therefore, RT 3, (RT 1)' the newly prepared alloys and Everdur Metal have a comparatively good resistivity against 30% HCl. In the case of boiling 20% HCl the resistivity of those copper alloys containing a small amount of Cd, Sb or Zn and newly prepared alloys BDGL 2 and (RT 1)' was found to be better than that of pure copper but inferrior to that of Hastelloy A. In order to find good acid-resisting alloys such as Nemif, Nemic, Nemifcle, Nemicle and Necomicle (reported in 2 nd report), the writers prepared nickel-copper-alloys by addition of copper instead of iron in those acid-resisting alloys mentioned above, but some of those alloys were found to be generally inferior, due to the excess amount of copper, although it is clearly known that the addition of a small amount of copper in nickel alloys for example 0.5_??_3% is very effective.

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For the synopsis of this work see the Report I [This journal 2 (1938), 118]

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The promoting reaction of BaCO₃ can be observed even when BaCO₃ and iron piece to be cementated by CO gas, are placed separately in a cementating chamber. This fact is explained as follows: CO gas formed in the system will be at first adsorped on surfaces of BaCO₃ crystals and then decomposed as
4CO=C₃O₂+CO₂
C₃O₂ thus formed will be desorped into a gaseous phase and perhaps partially polymerised and decomposed by the reaction
C₃O₂=C₂+CO₂
where C₂ will be in gaseous state, as A. Klemenc (4) observed. By the diffusion and dissolution of this C₂ gas into the iron piece, a solid solution is formed.

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