In this paper, the author discusses some problems on the tool velocity in the coal and rock cutting. A review on the present state of the tool velocity of various coal getting and rock tunnelling machines is firstly given. The test results by many authors about the effect of cutting speed on the cutting force are discussed. Most of them, with some exceptions, have shown that the cutting force does not depend upon the cutting speed.
Considering with the feed velocity of machines and the effect of depth of cut on the cutting force, the effect of cutting speed on the specific energy consumption is also discussed, to be suggested that a slower cutting speed is more desirable.
In order to reveal the reason of the independency of cutting force with the tool velocity, the propagation velocity of brittle crack in the rock sample is calculated. As a result of these culculations, it is shown that the crack velocity is more than several hundreds m/sec, and much higher than the practical range of tool velocity.
The effect of the rate of loading on the failure stress of rock is discussed to show that the rate of stress generated in the practical rock cutting could not affect the failure stress. This suggests that. the cutting force does not depend on the tool velocity.
Noticing the effect of tool life on the cost of rock cutting, the effect of tool velocity on the tool life or specific tool wear is discussed. It is concluded that most of the energy consumed in the rock cutting is converted into the thermal energy to generate a high temperature in the cutting tool.
Finally, using the dimensional analysis, the effect of tool velocity on the tool temperature is discussed, to show that the tool temperature is proportional to the tool velocity. Thus, the higher tool velocity would result in the higher tool wear and shorter tool life.
Remembering that the cutting capacity for most machines does not depend upon the tool velocity, it is concluded that the slower tool velocity is the better, concerning with the cutting force and the consumption of cutting tool.

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The minimum electric power for ignition of fire damp was measured, when the line of the transistor type-Induction Radio was cut off.
The results obtained are as follows
1) For 150Ω of impedance (Z) of the out put transformer, the minimum ignition-power was about 24VA. Therefore, it might be thought that the induction radio with out put of about 5VA actually used in the coal mines is safe for ignition.
2) Connecting the coil to the end of the line, the minimum ignition power was decreased by inductance (L) of the coil and the inductance of 0.04mH lowered ignition power by about 10%. The circuit with the coil (0.04mH), which experimentally resulted in the lowest ignition power, may not be in danger yet at the decrease of about 10% of the ignition power. Otherhand, connecting a transformer in the inductive line, the minimum ignition power was increased in order to the self power loss of the transformer.
3) If we go to use the transistor type induction radio with about 5VA out put in the coal mines, the impedance of the out put transformer in the radio circuit should be lower than 200Ω.

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This paper is the first piece of a serial work dealing with the results of a study made on a new type magnetic separator. It is devised to separate iron sands by-product from a slurry carried through a pipe line.
The results obtained from this investigation are as follows.
(1) The ratio of enrichment and the recovery of separated iron sands are subjected to the effect mainly from the shape of magnets, the arrangement of magnetic poles and the rate of volume flow in the by-pass pipe.
(2) The ratio between the rate of volume flow in the bypass pipe and that of in the main pipe, ranging from 0.0151 to 0.0454 is sufficient for the purpose of magnetic separation.
(3) When the magnetic separation has been carried out under the condition of mean magnetic flux density of 1, 000 gauss and 3-4% assay of feed, the ratio of enrichment becomes 16.5, the recovery 56% and the yield about 3 to 4%, respectively.

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The action of oxygen on the adsorption of xanthate at the sulphide mineral/water interface was investigated using galena as a test sample.
It is recognized that the elemental sulphur is produced on the sulphide mineral surface and the galena suspension becomes more basic when it contains the dissolved oxygen.
The reaction by which the elemental sulphur and OH- ion are produced in the suspension containing the dissolved oxygen is considered thermodynamically as follows.
PbS+1/2O₂+H+=Pb⁺⁺+S°+OH^-
The formation of the elemental sulphur closely correlates with the adsorption of xanthate on galena, especially with the incipient rate of adsorption of xanthate in the suspension of the various contents of the dissolved oxygen.
Accordingly, it is considered that the mineral surface is ionized positively by the above reaction and that the adsorption of oxygen on the sulphide mineral surface causes the improvement of the adsorption of xanthate on the mineral surface.

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From the pilot plant experiments for production of high purity deposited silicon rod, the following matters were revealed. Among various purifing processes of trichlorosilane, such a process was most excellent that the raw trichlorosilane was primarily rectified after phosphorus in it was converted to POCl₂·AlCl₂ and the purified trichlorosilane was rectified secondarily just before it was used for depositing silicon. Among various purifing processes of hydrogen, such a process was most effective that the raw hydrogen was washed with sulphuric acid solution containing an oxidizing agent, e. g. K₂Cr₂O₇, subsequently with KOH aqua, thereafter moisture and oxygen in the hydrogen was removed by common process, and finally thus purified hydrogen was washed with the purified trichlorosilane. This purifing process of hydrogen was not less effective than the process in which hydrogen was diffused through a paradium diaphragm. As the material of reaction vessel, the water cooled stainless steel was satisfactory. The vessel should be so constructed that the all parts of vessel except the silicon rod heated by direct passage of electric current were cooled sufficiently by water, and the parts heated unavoidably should be made with transparent quartz. When the trichlorosilane and the hydrogen purified by above stated process were used, the deposited silicon rods produced in the reaction vessel of pilot plant had the resistivities higher than n 150 ohm cm and carrier lifetime longer 200μsec after 2 zone passes of floating zone refining in argon.

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It is reported that the Gadeau's bath (molten salts of sodium fluoride-barium fluoride-aluminum fluoride system) is more suitable for the aluminum refining when a small amount of sodium chloride is added.
In this paper, the densities and the melting temperatures of some compositions of the quaternary molten salts, sodium fluoride-sodium chloride-barium chloride-aluminum fluoride system, were determined.
(1) The values of the densities of this quaternary system ranged 2.2-2.5g/cc at 800°C. These values decreased with the increase in the content of sodium chloride and increased with the increase of the content of barium chloride.
When the contents of sodium chloride and barium chloride are kept constant, the maximum density is observed at the point where the mole ratio of sodium fluoride to aluminum fluoride corresponds to 3: 1 (3NaFE·AlF₃).
(2) In this quaternary system, assuming the additivity of the density to be applicable and the following displacement
NaF+BaCl₂=NaCl+BaFCl
to occur in the melt, it seems that the calculated densities are accord well with the measured ones.
(3) Isothermal liquidus line of this quaternary system has a likeness to that of sodium fluoride-barium chloride-aluminum fluoride ternary system when the content of sodium chloride is kept constant, but the melting temperatures are lower than the latter on the whole.
And the melting temperatures of some composition ranges are about 650°C.
(4) It is preferred that when this quaternary molten salts are used as an electrolyte of aluminum refining, the contents of sodium chloride must be less than 10% as far as densities are concerned.

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This paper presents the reducing mechanism of recovering nickel from garnierite ores by the Segregation-Magnetic Separation Process from both side for viewpoints viz. chemical reactions and physical phenomena.
By segregation roasting, metallic nickel as well as iron and cobalt are reduced in two ways of direct reduction in situ and of turning steps combining chlorination, volatilization and hydrogen reduction of these vapors.
The ratio of the earned metal amounts by two ways depend on the operating conditions including temperature, retention time and blended reagents, such as reductants, water vapor and mixed chlorides.
For optimum segregation, garnierite ores calcined at about 900°C are in preference to raw ores, by reason of higher speed chlorination rate compared with a lower speed of direct reduction at the processing temperature range from 950°C to 1000°C.
Physical phenomena, for example, formation of some fused mixed chlorides, vaporization bf them, mineralizing effects of vapor and melts, adsorption of chloride vapors upon carbon, metels, alloys or gangue preferentially, formation of metallic whiskers and growth of them, were studied by XMA and an electron beam scanning microscope refered to the segregated particles after separation by means of magnetic concentration method.

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