The object of this research is to leach copper out of pyrite cinder and to utilize, at the same time, the residue as a superior raw material for pig manufacturing. In these experiments we used neutral ammonium-chloride solution as a leaching liquor.
The experiments were unsuccessful for both the teaching of copper and the desulphurisation of the ore in the original states. We confirmed the fact that most of the copper in the original cinder are in the forms of ferrites, which are unable to leach with the use of ammonium-chloride solution
For the purpose of separating the sulphuric and sulphurous compounds and SiO₂ from the iron oxides in the cinder, we first attempted to reduce the cinder by CO gas. After the reduction at a temperature from 450° to 500°C for 30 minutes, we found that nearly 95% of the non-magnetic iron oxider in the cinder were changed in the magnetic form. By means of a magnetic separator, we could separate the sulphur compounds and SiO2 from the magnetic part of the cinderhe concentrate being of Fe 67%, Cu 1-2%, S 0·01-1·5% and SiO₂ 1-2%.
The concentrate contained more than 90% of the copper content in the original cinder, and these copper compounds could scarcely be leached by the above mentioned solution because of the formation of Cu₂O·Fe₃O₄, etc. But, if we oxidise again these concentrates at 550°-600°C. for 30-40 minutes under air current, most of the sulphur burns to SO₂ and the suephur content in the concentrates lowers to about 0·01-0·50%, and moreover nearly 100% of the copper compounds change to the form easily leachable by the use of ammonium-chloride solution.

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1) Inverse chill of pig iron (Umgekehrter Hartguss). Some years ago, the author investigated the inverse chill of pig iron and published the result. He found that iron oxide in the sample greatly favours the inverse chill and explained the phenomena by the double equilibrium diagram of iron and carbon.
He studied since the effect of cooling rate and nature of pig iron on the inverse chill. and found the following facts.
Some pig iron is very liable to inverse chill, but when it is melted in the reducing atmosphere, it becomes not to show the phenomena unless it is cooled more rapidly.
The inverse Chill can be produced at will by adjusting the cooling velocity and the crystallizing velocity of the graphite eutectic of the sample, the latter varies with the composition and is greatly retarded by iron oxide content.
2) Sparks of molten pig iron When the molten Swedish white pig iron was cooled in air, sparks were shot up in the air from the surface of the molten metal during a certain temperature range and until solidification occured. When hydrogen or nitrogen was blown on to the top surface of the molten metal, these sparks ceased. Silicon or manganese addition prevented the sparks from being emitted, whilst blowing air accentuated the sparks. From the above facts, it was sujested that, these sparks are not due to gases absorbed by the metal during melting at higher temperatures, but to the oxygen in the air reacting with carbon in the metal.
3) Effervescence of molten pig iron The Swedish white pig iron was melted in a quartz tube containing hydrogen, and keeping the temperature of the molten iron at about 1250°C, the gas was evacuated from the tube by a vacuum pump. During the evacuation it was observed that the molten pig iron vigorously effervesces. When the gas was almost evacuated the effervescence ceased. Hydrogen was then put in the tube and again evacuated This operation was repeated until the effervescence became not to occur any more. In some pig iron, the operation had been many times repeated before tbe effervescence came to an end, but in some pig it did not appear from the first time. From these facts, it is sujested that the effervescence is not due to the hydrogen absorbed by the metal, but to iron oxide in the molten iron.

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The present investigation was carried out to make clear the relation between the growth of grey cast iron due to the abnormal expansion at Ar transformation and that due to the oxidation. Various kinds of dilatometer were used for this purpose. According to the authors' results, when grey cast iron is repeatedly heated at a high temperature in air, growth takes place principally due to the oxidation and the growth of this kinds is much larger than due to the abnormal expansion at Ar transformation.
It is acceptable that grey cast iron becomes susceptible to oxidation by passing through its Ar critical range, hence its growth is accelerated by the oxidation. The authors cannot, however, agree with the investigators who believe that the abnormal expansion at Ar tranformation in a direct cause of growth in every case, the effect of exidation being indirect.

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In order to measure accurately the effects of various elements on hardening of steel, experiments for gas hardening under varied conditions were carried out, using a special device invented by the author.
The effect of carbon upon carbon steel was first investigated, and then the influence of Mn, Ni, Cr, W, Mo, Si, Cu, V, Al, Ti, Co, Zr, Be and U on steel with a constant carbon content. The author having succeeded in the most accurate quantitative measurement on the effect of each element, the results are described in this paper.

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