In order to determine the composition as well as the crystal structure of the main hardening element of duralumin, the so-called “S” compound, seven specimens, having the composition near the compounds Al₁₃Cu₇Mg₈ and Al₅Cu₂Mg₂, have been prepared, and the X-ray analysis as well as the microscopic examination have been carried out. The results showed that the “S” compound has the composition Al₅Cu₂Mg₂ and that the compound belongs to the tetragonal lattice, containing 18 atoms or 2 molecules of Al₅Cu₂Mg₂ in each unit cell, the lattice constant of which is found to be a=5.71±0.04Å, c/a=1.39.

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The present writer studied the castability of Lautal, measuring the running quality, shrinkage and mechanical properties.
The results obtained may be summarized as follows:-
1. The running quality of Lautal is relatively small.
2. The effect of addition of a small amount of metals on the shrinkage of Lautal A (4% Cu, 2% Si) is small, but in the case of Lautal B (3% Cu, 7% Si) generally reduces the shrinkage.
As the degree of super heating increases or the cross sectional area of the bar poured increases, the shrinkage increases; on the contrary, the increase of riser reduces the shrinkage.
3. The suitable casting temperature for the Lautal A is found to be 740° and for the Lautal B 690°. The addition of Fe increases the tensile strength of the Lautal A, but makes the Lautal B brittle. The addition of Mg has no influences on the properties of the Lautal A, but increases the strength of the Lautal B; on the contrary, the addition of Mn has no influences on the Lautal B, but increases the strength of the Lautal A. The effect of the addition of Ni is not noticeable.

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Ba sed upon the results obtained concerning. the A₃ transformation of Fe-Ni alloys, some remarks on the transformation of austenite in carbon steel have been made, namely: (1) how the quantity of retained austenite in oil quenched specimen becomes greater than that in water quenched one, (2) what is an essential difference between the primary and secondary troostites, (3) on the cause of the irreversibility of the A₃ transformation found in Fe-Ni alloys, and (4) martensite is a metastable α solid solution situating below the extension line of the solidus of A₃ transfnrmation in the Fe-C diagram.

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The present writer investigated the equilibrium relation of the ternary system Cu-Al-Fe from the Cu-Fe side up to the Al-content of about 20% by weight. The results obtained may be summarized as follows:-
(1) In the ternary field herein studied, there exist 3 non-variant reactions, viz.,
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(2) The mono-variant curve of the peritectic reaction Melt+δ-Fe_??_γ-Fe, originated from the Fe-Cu system, passes along the Fe-Cu side, and reaches the non-variant reaction at 1072°.
(3) The eutectoid change γ-Fe_??_δ-Fe+α originates from the Fe-Cu system also reaches above mentioned reaction, rising its reaction temperature with the increase of Al-content.
(4) The mono-variant peritectic reaction, originated from the Fe-Cu side at 1094°, passes almost parallel to the Cu-Al side, lowering gradually its reaction temperature with the increase of Al-content.
(5) The eutectic reaction Melt_??_α+β of the binary Cu-Al system continues up to the di-peritectic reaction at 1048°.
(6) The eutectoid change β_??_α+γ of the binary Cu-Al system together with the ones, β_??_α+δ-Fe and β_??_γ+δ-Fe, makes the ternary eutectoid change at 568°.
(7) In the mono-variant curve of the peritectic reaction Melt+δ-Fe_??_β, there is a peak at 1075°, its composition being Al=13.5, Fe=6.5% and Gu bal. by weight.
(8) γ-Fe appears as primary crystal in the narrow domain, whereas the primary surface of δ-Fe spreads from Fe-Al side to the Cu-corner.
(9) At high temperature, both α and β dissolve some δ-Fe, and precipitate it in the cooling.
(10) The globular phase found in the micro-structure of the industrial iron-bearing aluminium bronze is δ-Fe containing Cu and Al as solid solution.
In the appendix author discusses the role of iron in the industrial aluminium bronze.

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The quantitative spectral analysis of alloys generally accompanies many difficulties, that is, in the “Relative method”, (1) many standard samples are necessary, (2) the spectral lines should he in a suitable darkness, and (3) the application for metallic specimens is very limitted, and in the “Absolute method”, the line series of homologous spectrum can't be obtained very easily. Therefore, in order to make the analysis more simple. and convenient, the present experiment was carried out to obtain the relation between the intensity of a spectral line and it, effect (blackening) from the “Characteristic Curve” of the photographic plate under the assumption that the concentration of alloying elements is proportional to the intensity of the spectrum. The results of the experiment show that the present method is quite satisfactory for practical analysis. For example, in the Relative method, the required number of standard samples is rnuch less than that of the ordinary method, the blackness of the spectral lines may be applied for a wide range, and the range of the concentration of an element to be analysed is much extended, and in the Absolute method, the line series of the homologous spectrum can be obtained quite easily.

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