Swedish white p'g iron was first used as the sample. It was melted in the nitrogen atomosphere at every temperature up to 1, 450°C, and the graphite content of the melt was observed. From numerous experimental results, the author introduced the following theory for explaining the variation of graphite content with respect to the melting temperature.
The reduction of oxides in the sample which hinder the graphitization by its carbon, will promote the graphitization. The carbonmonoxide thus evolved by the reduction will also directly promote the graphitization and by expelling such gases as N₂ or H₂ which hinder the graphitization from the melt, will indircctly promote it.
Some experiments were made to confirm this theory. The author carried out also the same experiment with samples of Swedish white iron adding each element. He found that a marked increase of graphite content of the melt at a temperature range of 1, 400-1, 450°C, occured only in both the samples of Swedish white iron with and without addition of silicon.
In the case of the samples containing each element which forms a stable carbide or makes pearlite stable, the variation of graphite content with respect to the temperature is in a considerably less extent.
Each sample containing 1%Cr, 4%W and 4%Mr, showed a critical melting temperature of about 1, 200°C, below which the melt became completely white but above which it became completely gray. The author c nfirmed these phenomena to be due to the chilling effect of oxygen.

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In the theoretical chemistry for steel melting, only the equilibrium-constants for the chemical reactions has been hitherts dealt with. The author considers, however, that this problem is not so simple, whilst no body ever attained to its practical solut on.
The problem for steel melting must be a problem to find the condition of equilibrium for the whole system of slag and metal at their practical temperatures. Varous chemical elements and chemical compounds exist both in the steel and the slag. At the surface between them various physical phenomena and chemical reactions take place and all these phenomena should mut ally be in an equilibrium.
In this paper, are described the theory of such chemical equilibrium and its practical applications for the theoretical analys's of the actual steel-melting.

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In the persent experiments, the author has investigated the effects of the eight elements, other than those already described in the First Report, upon hardening properties of steel. These effects have been found to be classified into three groups as in the case of the First Report.
The first group:
The depth of hardening increases as contents of elements increase. To this group belong B, P, Sn, Sb and Zn.
The second group:
The depth of hardening increases as contents of elements inerease to a definite limit, beyond which the reverse effect appears. To this group belongs Ce.
The third group:
The penetration of hadening decreases as contents of elements increase. To this group belong S and Se.

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The following equations of the carburizing equilibrium have been confirmed by many investigators.
3Fe+2CO Fe₃C+CO₂[Fe-C-O System]
3Fe+CH₄ Fe₃C+2H₂[Fe-C-H System]
Lately Mr. Madono presented the opinion in which he asserted the carburizing equation should be represented as follows:
(Solid Sol.)+2CO (Solid Sol.)+CO₂
(Solid Sol.)+CH₄ (Solid Sol.)+2H₂
On account of the unstableness of Fe3C, after iron or steel is saturated with carbon the equilibria coincide with 2CO C+CO₂ or CH₄ C+2H₂. He carried out experiments on carburizing of the electrolytic iron sheet for a long time at various temperatures with the solid carburizing mixture, and the result obtained was that C contents absorbed in the iron sheet coincided with the saturated concentration of graphite in austenite. He cosidered that this result proved the truth of his own theory.
The authors also carried out carburizing experiments with the electrolytic iron wire, 0·5mm thick, by pure CO gas, and found that at a temperature below A1 point the formation of Fe₃C was surely recognized by means of magnetic and X-ray analyses, and at a temperature above A1 point C was absorbed over the saturation value of that in austenite. In considering this fact, the authors supports the old theory of carburization. In the case of the pack carburizing, however, the carburizing action stops when C% reaches the saturation value at any temperature, but this fact does not suggest the carburizing equilibrium to be 2CO C+CO₂ in all cases.

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