This paper describes the method for detecting “loose” or “drummy” rock, analyzing a sound of rock electroacoustically.
In this study the authors divided each sound every one-third octave through thirteen filters of which the frequencies are 4000 to 6, 300cs, and tried to discriminate better between solid and drummy rock, using “Integrator”. Here “Integrator” is an instrument made to measure electronically an equivalent to the area surrounded with the envelope of the wave form and the axis of the time.
By this method the following results were obtained.
Applying this method to sounds of several kinds of rocks, solid and drummy rocks of them were generally discriminated well; for example, in the case of slate the ratio of the mean value of the quotients of the areas of the filtered wave forms divided by the areas of the unfiltered wave forms of drummy rocks to that of solid ones was even more than 20db., when the filter frequency was 500c/s.

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Wet sized samples of magnetite and hematite of 150-200, 200-270, 270-400 and<400mesh sizes were rolled into green balls in a horizontal drum of 30cm inside diameter and of 10cm length. The crushing strength of the balls was determined on a balance.
It may be postulated that the fineness of ore particles is an important factor which affects the optimum moisture content as well as the crushing strength of the ball. It has been found that for finer ore particlesthe strength is higher and the critical range of optimum moisture content is narrower. The optimum moisture content for magnetite is slightly higher than that for hematite. It seems, however, that there is no substantial difference between magnetite and hematite in rolling green balls. This has been verified from the results of specific surface determination for magnetite and hematite.
It is interesting to note that the strength of the ball made from ore particles which had been treated with sodium oleate solution is appreciably lower than the strength of untreated one. This has been considered to be due to the effect of hydrophobic film of sodium - oleate on the surface of ore particles. There is also no appreciable difference between magnetite and hematite in the effects of sodium oleate treatment.

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For process control of flotation operation at Taro concentrator (lwateken, Japan) the routine analysis procedure of flotation samples by fluorescent X-ray spectro chemical method has been established. The use of this system has offered good chances for improvement of the process.
The samples examined are of 22 kinds, i. e. flotation feeds, concentrates and tailings of the bulk-differential flotation process, and these are consisted of pyrite, zincblende, gdena and chalcopyrite but oxidized mineral. The X-ray spectra observed are as follows: Fe-K_β1, Zn-Kα, Pb-L_β1 and Cu-Kα. The samples are prepared only with drying and deviding.
The routine 3 shifts analysing operation is carried on shift samples (22 kinds) and on the it portant batch samples (10 kinds, twice a shift), but if necessary the time lag between sampling and report of analysis can be reduced to as little as half an hour. Accuracy of the routine analyses is described. The very gain by the X-ray analysing system is advanced performance of the flotation operation, it results in reducing variation of the process, improving grade of concentrates (particularly zinc concentrate), and decreasing tailing losses.
Furthermore, a relationship is derivered between particle size and intensity (iron and lead) of the flotation feed (product of the pnmary grinding circult). Using this relationship it would be posslble to deck the slze distribution of the. sample examined in grade ofter grinding it.

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The activity coefficients of zinc oxide in molten slags of FeO-Fe₂O₃-SiO₂-ZnO and FeO-Fe₂O₃-SiO₂-ZnO-CaO were measured at about 1200°C.
A molten slag was brought into equilibrium with a gas mixture of CO, CO₂, and Zn vapor which was prepared by passing a CO-CO₂ gas mixture through a layer of pure ZnO pellets at about 1000°C. According to the desire to study the slags both saturated and not saturated with silica, crucibles of silica and platinum were used respectively. The molten slag, equilibrated with the gas mixture, was quenched in the flush of Ar gas and analysed for FeO, Fe₂O₃, SiO₂, ZnO, and CaO.
It was found that the activity coefficients of zinc oxide did not change so much as the variation of the composition of the gas mixture and that for the slags which were not saturated with silica they multiplied from 1.8 to 3.1 with the increase of the content of CaO from zero to over 16.5 weight per cent. In case of silica saturated slags, the addition of CaO varied only the saturation concentration of silica and the activity coefficients of zinc oxide were about unit.

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