Shear tests were performed on a powder bed made of a dispersed powder and of an agglomerate powder, respectively. These results are compared each other, and the effects of agglomeration on the flowability of the powder are discussed. In the region of low preconsolidation stress, agglomeration affects the results of the shear test, that is, when the powder exists as an agglomeration, the shear stress of failure is lower, and the slope of P. Y. L. is smaller. For the dispersed powder, the flow index (FI) obtained from the results of the shear test is nearly constant and not greatly affected by the preconsolidation stress. It was shown that for the cohesive and agglomerate powder, FI is considerably affected by agglomeration, that is, the value of FI increases as the preconsolidaton stress becomes larger.

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The influence of pH and the concentration of dispersants on the coagulation and dispersion of fine particles in water is dealt with in this paper.
By using the Derlaguin-Landau-Verwey-Overbeek (DLVO) theory and the bulk zeta potentials at pH values, the coagulation values are obtained. The analytical results are compared with both the experimental ones obtained using roseki and talc as well as with data in the literature. As a result, the calculated and experimental values for quartz, feldspar, limestone and talc are found to be nearly coincident, but the calculated coagulation values for kaolin, bentonite and roseki representative of clays are recognized to differ somewhat from the experimental ones in the acidic region. It is considered that a cause for the discrepancy may be the oppositely charged potentials on the face and edge of the clays in the acidic region.
The influence of pH and the concentration of dispersants on the dispersion of some sorts of fine particles in water is shown to be explained semi-quantitatively by the DLVO theory. In particular, it is shown that the optimum concentration of a dispersant obtained experimentally is approximately in accordance with the concentration of the dispersant showing the maximum total potential energy calculated from the DLVO theory which is coincident with the one showing the maximum zeta potential or with the one showing a zeta potential a little lower than the maximum.

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This paper is concerned with the the efficiency of four types of hummer crushers and the size of the crushed wood particles. The relationships between the power requirement of the crusher of screenless and screened hammer mills were also examined.
Three types of screened hammer mills and one type of screenless hammer mill, were examined.
The main variables of the crushers were the scale of the mill, the screen opening, and the rotational speed.
The relationships betweeen the efficiency and the handling condition of the crushers were as follows:
H_u/τ₀=r₁(D_v/d_v-1)^-1(Rω²)^2/3
where r₁ was experimental coefficiant. It was 7.8×10^-5 for wood, and 7.0×10^-4 for the bark of spruce.
The size of the crushed particle, d_v, was expressed as follows:
d_v=r₂(S_d)^1/2(Rω²)ⁿ
where r₂ and n were experimental coefficients. They were 2.6, -1/2 for wood, and 0.46, -1/3 for the bark of spruce.
The power requirement for crushing wood was found to follow Kick's law for the four types of hammer mills examined.

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The coefficient of friction introduced as the constant depending on the combination of solid particle and pipe material is considered. This investigation provides that the coefficient of friction is equal to the sum of both the coefficient of pressure drop caused by the friction and the collision of particles at the pipe wall as well as that caused by the mutual collision of particles in the flow. Using the experimental results of the pressure drop in the steady region of the flow over a wide range of solid properties and pipe diameters, the value of the wall friction has been obtained for each combination of solid and pipe material.

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The mass size distribution of respirable coal dusts has been studied by using micron photo sizer. The respirable coal dust samples were collected at the mine atmosphere during drilling in coal seams by using Messrs. Casella's ‘hexhlet’ apparatus specially designed and fitted with horizontal elutriator to collect the respirable coal dust fraction simulating to the lungs retention conditions of the coal miners. The results showed that the distributions are unimodal, asymmetric and positively skew, with modes usually between 2.5 and 2.9μm equivalent spherical diameter.
Although the assumption of log-normality was useful in interpreting the results, closer observations indicated that the relationship between the size and weight frequency of the particles can be represented by a second degree parabolic equations, W=α+βS+γS², where W and S are weight frequency and size of the particle, and α, β, γ are the constants. The equation characterizes the mass of the respirable particles if the size is known.

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