The effect of the addition of light anhydrous silicic acid to potato starch powdes, which improves the lubricating characteristics of drug powders, is usually cancelled by the absorption of moisture. In order to improve this point, hydrophobic light anhydrous silicic acid was used, and prevention of the loss of the lubricating effect by moisture sorption was examined.
1) Moisture sorption of the mixture of dry starch and silicic acid (0.1%) results in the increase of the apparent specific volume and angle of repose, and decrease of dispersibility, with the increase in water content. The resultant mixture shows powder characteristics close to that of starch, that is the lubricating effect of light anhydrous silicic acid is lost. When 0.1% hydrophobic silicic acid is added, its effect was almost the same as when added to moistened starch, and the lubricating effect of hydrophobic silicic acid was not lost due to moisture sorption by starch.
2)Examination of such mixtures by a scanning electron microscope revealed that ordinary light anhydrous silicic acid stuck to starch granules that looked like the moistened thin paper to be stuck when light anhydrous silicic acid experienced moisture sorption, and light anhydrous silicic acid could not prevent the contact of the starch granules. This resulted in the reappearance of powder characteristics in starch itself. In the case of hydrophobic light anhydrous silicic acid, the particles do not stick to or fall from starch granules even after moisture sorption and remain attached sterically to the starch granules the same as after their addition, and prevent the contact of starch granules themselves. This is considered to be one of the reasons why hydrophobic light anhydrous silicic acid does not lose its lubricating effect.

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Storage of the 10cm diameter bored four air-blowing nozzles (diameter 1mm) in contact with a wall in order to discharge the powder from the bottom was done. The air in the storage is expected to blow away the powder from the wall near the nozzle position and to break the bridge by fluidization.
Some experiments were performed to investigate the characteristics of mass flow rate of discharge by various air flow rates, heights of the packing bed and heights of the nozzle position using talk powder. As a result, it was shown that 1) the discharge of powder could not occur if the height of the packing bed was lower than a certain value which was higher than the nozzle positron, 2) the mass flow rate of discharge promoted with the height of the packing bed, and 3) the mass flow rate of discharge experienced little change due to the air flow rate.

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The behavior of the impact fracture of glass bead was investigated by a shot life tester of the centrifugal blowing-force type.
The projected particles were divided into two casses, fractured and non-fractured by the use of a standard mesh of 1410μm.
Projecting and classfication were repeated until non-fractured particles were fractured.
In each operation, the weight and size distributions of non-fractured and fractured particled were measured, respectively.
The results are as follows;
1) The relationship between the relative weight of non-fractured particles and the number of projectors is shown by a straight line on the Weibull's chart.
2) The size distribution of non-fractured particles is influenced neither by the number of projections nor by the revolution rate of the impeller when the higher impact force is applied to the particles.
3) A surface fracture occurs when the weaken impact force is applied, and the diameter of a particle decreases without losing its spherical shape.

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Detail knowledge is required about the plastic properties of slurries, stress removal of a particles network with time, and so on in conjugation with their visco-elastic properties to develope analytical discriptions to the slurry processes.
A new cone and plate type apparatus was developed. It covers both shear test and usual thixotropic measurement. In the shear test, the plate was rotated at an extremely slow rate from rest and stopped after causing small distortion. The system was driven by a function generator, print motor and feed back control unit and multi-stage gear unit. The rotating angle of the plate and cone were measured with time at 0.03 degree accuracy. Bentonite-water of 16.81wt per cent slurry was examined as a sample.
The result of a shear test was favorable reproducibility and showed that this slurry behaved almost completely like an elastic boby with small distortion. Creep or yield phenomenon was observed at levels over the limiting strain of elasticity.

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