In this report, the author gives the results of measurement of magnetic susceptibilities of pyrrhotite from the following are deposits by the apparatus using alternating current;
i.e. Chichibu Mine (Saitama Pref.), Yanahara Mine (Okayama Pref.), Kawayama Mine (Yamaguchi Pref.), Komori Mine (Kyoto Pref.) and Futaba Mine (Hyogo Pref.).
The main results obtained from measurements of solid test pieces using A. C bridge method, are as follows:-
(1) The magnetic susceptibilities of pyrrhotites from these mines measured by the above method range from 18000×10^-6 to 280000×10^-6, and are greater than the values obtained by ordinary magnetometer method- with powdered samples.
(2) The range of the values of magnetic susceptibility of pyrrhotite is almost constant within the limitted range of frequency, irrespective of their types of deposit or.their occurence.
(3) Generally, magnetisms of the samples from the Chichibu mine and the Kawayama mine have the wide distributions from weak to strong.
(4) On the other hand, pyrrhotite from the hydrothermal deposits such as Yanahara, Komori, and Futaba mine show narrower range of magnetic susceptibility.
(5) It seems that there is no relation between the variation of magnetism and the difference of level hight except: the Yanahara mine.
(6) The values of magnetism of pyrrhotites which associate with pyrite are strong as described by Dr. Kiskyras, and those accompanied by magnetite, arsenopyrite and skarn minerals are weak.
(7) At the Chichibu and Kawayama mines, pyrrhotites near the copper and zinc rich zones have the tendency to show a special distribution of magnetic susceptibility and always have a stronger mean value.
(8) In the hydrothermal deposits, pyrrhotites which associate with chalcopyrite or sphalerite, seem to have a characteristic distribution of magnetic susceptibility.
(9) The above mentioned facts-(3)(4)(6)(7) and (8)-suggest that the strength of magnetism is related to the associated minerals, and therefore, it.can be said that magnetism of pyrrhotite relates to the types of deposit and their occurences.

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It is very important to obtain a knowledge of the exothermic phenomenon of coal at low temperature, because it represents much better the initial state of spontaneous combution. In the previous paper, th6 writers stated that the following equation would exist in relation to the shape of cracks or roadways and the heat of oxidizing reaction:
4·L·b·G/d·w·γ·cν=K∫θLa/θeθ₀dθ
where a and K are constant values relating to the reaction which shall be determined in this experiment, for a definite relation must exist among the values of the length L, the diameter d and the air velocity w at such a roadway as any spontaneous combustion does not occur
In this experiment, the writers first measured the velocity of heat generation as well as the temperature rise of coal, and then its heat value at low temperature, from which results it was recognized that the half of the heat generation should be originated from the oxygen absorption of coal in a wet atmosphere.

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The surface areas of mineral particles are measured by gas-permeability method, its shape factor being estimated against the variation of particle size. From the results of experiments, magnetite and chromite seem to have considerably large value of shape factor under 270 mesh, different from many other minerals such as fluorite, gypsum, galena etc.
The areas of same samples as determined by gas permeability method are measured by B. E. T. method of nitrogen gas adsorption experiments. Then, the insensitive 'characteristics of permeability method, compared with B. E. T. method, are illustrated.

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Mechanism and Kinetics of the roasting reaction of zinc blende were studied by measuring the change in weight and gas analgses at temperatures from 500°to 925°C. The results obtained are as follows:
(a) Oxidation:
An experimental equation, on the rate of oxidation was
1-(1-x)1/2=kt (825-900°C)
where x is the amount of S reacted/total amount of S in sample and t the time. The activation energy calculated was about 8.8 kcal, thus it was considered that the rate determining step inthe present oxidation would be the rate of diffusion.
(b) Sulphatization
The quantity of sulphate produced and the rate of sulphatization were calculated from the relation between the change in weight and the results of gas analyses. It was concluded that the present sulphatizing reaction obeyed an indirect process in which the sulphatization follows the oxidation.
The conditions for the muximum rate of sulphatization and the effects of the roasting atmospher being SO₂-O₂ or SO₂-air were also studied.

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