The metallic tungsten of the highest purity has been required in the fields of hard metals, electronics and special alloy steels, so the ores which includethe impurities only a little have been selected as the raw materials.
But the low grade complex ores containing many kinds of impurities such as Mo, P, Cu, Sn, Ni, or As, of Ôtani Mine were treated successfully by the improved processes to yield the high purity metal.
The physical treatments of the gravity concentration, the flotation and the electrostatic separation were applied and the concentrates of W0₃, Cu-sulfide, Fe-sulfide and Sn+WO₃ were obtained at a high recovery. The concentrates of WO₃ and Sn-i-W00 were treated by the method of the autoclave leaching of Na₂CO₃ solution at Kanzakigawa and the impurities above mentioned were removed from the leaching solution by the chemical methods and the artificial CaWO4 of the high purity were precipitated.
Furthermore this artificial CaWO4 was dissolved with HC1 solution and from this solution the WO₃ was prepared and it was reduced to metallic W in the hydrogen furnace.
At Uji factory the covered type electric furnace were adapted for smelting ferro-tungsten and by this method the flue dusts were completely recovered, so the total recovery percent of tungsten were incleased.
These procedures and also other refining methods or low grade complex ores from abroad are reported in this paper.

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In this report the writers describe the results of their X-ray study of Pyrrhotite, investigated withthe “Norelco” X-ray diffractometer.
The main results obtained are as follows:
(1) X-ray profiles:
a) Employing the X-ray diffractometer, the writers obtained detailed X-ray diagrams of pyrrhotite which would not be expected by the powder photographic method.
b) It was confirmed that the (102) diffraction peak breaks up into two peaks, when the crystal changes into ferromagnetic state from paramagnetic one.
c) The specimen with a similar chemical composition to the artificial pyrrhotite showed. almost the same α values.
(2) Relation between chemical composition, crystal strutucre and magnetism
a) The vacant Fe atoms in pyrrhotite crystal vary the chemical composition and decrease. the crystal symmetry too. Consequently the (102) diffraction peak breaks up and the occurs.
b) The point where both (102) _a, and (102) _b peaks indicate the same diffraction-intensity may be considered as the lithit of a, single phase of. pyrrhotite. At this point pyrrhotite shows. the strongest magnetism. If Fe atoms further decrease a new phase of pyrite grows up in pyrrhotite, crystal.
c) It was Proved by measurement of the susceptibility-temperature curves that the specimens showing the break-up of the (102) diffraction peak are magneticaly homogeneous each other.

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As a part of the fundamental studies on the underground pressure, we have engaged in the investigation on the creep of rocks, on which a few studies have been published. This paper describes our experimental and theoretical studies on the creep characteristics of some sedimentary rocks. The results obtained are as follows:
(1) Izumi Sandstone fails due to creep under the stress about 80% of its mean compressive strength lasting a long period of time. It is supposed that the similar tendency may probably be found in most sedimentary rocks.
(2) The creep characteristics of rocks are approximately explained by means of the Burgers model, from which an equation to represent the creep strain under relatively high stresses is derived.
(3) The constants concerning with the creep properties of shale, sandyshale and sandstone are determined.

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The motion of a Low-Head Vibrating Screen is considered to be a linear simple oscillation, if the reaction force which is equal to the weight of screen always acts on each fixed end of supporting ropes. But if the centers of gravity of unbalanced weights in vibrator have asymmetric arrangements, it becomes an elliptical orbit.
Taking the effects of supporting springs into consideration, the author developed theoretical equations (eq. 11 & 12) governing this motion analytically. Although the vibration varies with the velocity, it can be assumed as a linear vibration at the suitable velocity, and the orbit indicated by the author's equations is almost coincident with that of. a Low-Head Screen used in general practices.
In designing and manufacturing a Low-Head Screen, it is recommended to use a model machine, by which the vibration test is to be conducted applying the law of similarity the author proposed.

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The decopperizing process by leaching operation after oxidizing roasting of copper bearing nickel mattes may only be applicable to mattes containg large amounts of copper. Formattes with small contents of copper, a separation of nickel and copper by this process is not sufficiently and other proper methods must be designed.

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