Batchwise and continuous settling tests with raking action were made of several homogeneous flocculated slurries listed in Table 1, with experimental apparatus as shown in Fig.1 Performance results of continuous thickener are discussed in terms of the batchwise settling characteristics. Conclusions obtained may be summarized as follows
1) Continuous thickener with raking action should be designed on the information obtained from batchwise settling test made under the similarly stirred condition. Settling characteristics are markedly influenced by raking action.
2) Settling of such slurries with raking action is not the consolidation of their floc structures by compression as has been believed, but the mere settling due to their concentrations for the considerably wide range of concentration.
3) Relation between settling rate R and slurry concentration C may be computed from a few settling curves by the graphical method proposed by Kynch²⁾ and the authors⁴⁾ R-C relation under stirring condition may be represented with equation (3) for the range of high concentration.
4) Method of determining the settling area is discussed from two standpoints. One is based on the batchwise thickening operation as shown in Fig.6, and the other on the mass settling ve-, locity G [=C (R+Q_u/A)] of sludge layers of various concentrations. Thickening areas required from both the standpoints are proved to coincide with each other, provided that the settling curve and R-C relation of that slurry could be expressed by eq. (1) and (3) respectively.
5) Figure 7 shows the mass settling velocity G at certain Q_u/A as a function of slurry concentration. This curve shows the minimum value at C=C_mn which is the concentration of the capacity controlling layer in the lower part of the thickener. In this figure, C_fQ_f/A corresponds to the normal state of solid loading and in this case the underflow concentration to be obtained is C_u. If the solid loading per unit thickening area increases to C_fQ_f'/A, it becomes overloading and the part of the feed solid is carried out to overflow, but the underflow concentration remains constant at C_u. When the feed rate decreases to Q_f", it becomes underloading and the concentrated layer near the bottom of the thickener disappears and the underflow concentration will be diluted to C_u".
6) Sectional area of continuous thickener required to obtain the underflow concentration C_u when the feed rate is Q_f, may be determined graphically as shown in Fig.10. Product of C & R is plotted against C and the tangent PQ to CR-curve is drawn from the point S(C=C_u) on the C axis, which crosses the vertical axis at point Q. Ordinate of point Q represents the value of C_fQ_f/A, from which A may be computed.
7) It may be concluded from our experiments and considerations that the depth of thickened sludge or detention time has not the substantial effects on underflow concentration and thickening capacity, which contradicts the now prevailing conception of the effect of thickener height.

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Liquid-liquid extraction accompanied by rapid chemical reaction has been studied with water and benzene layers, gently stirred in a vessel under the condition known of interfacial areas. The rate of extraction is given by the following equations:
[1]
[2]
where N is the rate of extraction and q is the concentration of reacting substance in water. N increases with the increase of q linearly up to some critical value (Eq. [1]), beyond which it becomes constant, independent of q changes. (Eq. [2]). This is identical with CO₂ [Air]-KOH [Water] chemical gas absorption.⁵⁾
We added I^- ion to the water layer of I₂ [Benzene]-Na₂S₂O₃ [Water] system to make sure the influence of the increase of the distribution coefficient upon the extraction rate. In the stage of Eq. [1], the rate increased as had been expected, but no influence was observed in the stage of Eq. [2].
The action of KOH was the same as that of NaOH in the system of the organic acid [Benzene]-KOH or NaOH [Water].
Regarding some solutes, the effective film thickness of benzene xB(=D/kB) was calculated by means of Eq. [2], and the result proved that it was almost constant.

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Crushing test was conducted with a s1iding-friction apparatus shown in Fig.1, using cylindrical and powdery samples prepared from the same stoneware-plate as mentioned in the authors' previous report. When the sample was cylindrical, the quantity of crushed product removed by friction increased it direct ratio to the length of the grinding time and that of the running path, but when the sample was powdery, the same did not hold, as choke crushing occurred in this case.
The size distribution curve of removed products, obtained from friction crushing of the cylindrical sample may be expressed by Eq. (1), and so will be the one obtained from the model experiment shown in Fig.5 or that from the impact-compression crushing of the cubic or powdery sample. The authors have found close similarity among these, and have presumed that all three follow the same mechanism of crushing by mechanical rugged-surface-friction.
In considering the total quantity of powder obtained by sliding-friction crushing, both the crushed product and uncrusbed portion were taken up, where the inclination n of size distribution curve was found to change in accordance with the ratio of crushed product to the remains, and generally to be lower than that in the case of the impact-compression crushing.
Investigations into the variation of the quantity of samples removed by friction were also made in connection with initial particle size, roughness of friction surface and pressure and friction speed, and it was found that the greater were the friction-surface roughness and the pressure inorease, the larger would be the increase in and variation of the removed quantity, in relation to the initial particle size or friction speed, as shown in Figs.9 and 12.

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To know the flow characteristics of molten plastics is very important for the study and the practice of extrusion of the like materials. In the present research work, the flow characteristics of polyethylene (Eastman, molecular weight=23000) were obtained for the temperature from 160° to 200°C with a small screw extruding apparatus. The pressure was calculated from the strain of tension bar by means of a strain meter. The rate of flow was also measured. Thus, the correlation between the rate of flow and the pressure was obtained, according to which three flow constants in the theological equation¹⁾
were calculated by the Sakurada-Sone method⁵⁾ as shown in Table 1.
The merits of this method of viscosity measurement with the screw extruding apparatus are as follow:
1. Uniform heating and kneading effect are obtained by the stirring motion of the screw.
2. Continuous measurement is possibte and feed and change of test material are very easy.
3. Change of piston velocity which occurs in the "piston and cylinder" apparatus can be avoided.

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In designing an agitator we assume the effect of agitation to be expressed by the function of two terms, Q/V (volumetric discharge flow per unit volume) and P/V (power per unit tank volume).
The heat transfer coefficient may be represented by the following general equation, NN_u=f (Q/V, P/y)
where the volumetric discharge flow rate is calculated by using Eq. (1).
In the case where the fluid is water, Fig.4 & Eq. (4). are obtained by the use of Oldshue's general equation, Eq.(3), and these are employed for the computation of the heat-transfer coefficient of coil.
The Mack et al's data on dissolution of benzoic acid in water may be expressed by Eq. (7) This above mentioned method may hold good in many commercial mixing instances in Japan. With an ordinary mixing tank, the values of Q/V & P/V fall within the following range.
moderate mixing Q/V=3-5[1/min.] P/V=0.2-1 [ /m³]
strong mixing Q/V=5-10 [1/min.] P/V=1-3 [ /m³]

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