粉末薬剤のタッピングによる充てん

抄録

A new tapping folumula applicable both to coarse and fine particles was discussed in order to investigate the effect of internal friction and cohesive force among the powder particles on the tapping.
Sodium borate and boric acid (40∼800μ of mean particle diameters) were tapped in solvents, and thirteen other kinds of organic and inorganic fine powders in air and in solvents.
The following folumula was found to be applicable comparatively well to all the cases investigated.
-dε_n/dn=p{log1/(ε₀-ε_n)}^q-r
p, q, r: Constants
In sodium borate and boric acid, parameters p and r remarkably decrease, and q increases, with the decrease of the particle size in the region smaller than the critical size obtained for the loosest packing in each solvent. In the case of fine powders, the same tendency is also found for the dependency of the parameters on the angles of the repose. The presence of critical particle size has been confirmed below which the angle of the repose and porosity in loosest packing increase remarkably with the decrease of the particle size. This phenomenon can be explained by the assumption that the cohesive force among the powder particles are negligibly small in the region above the size, but it influences on the angle and porosity in the region below that. It is considered that parameters p, q and r are related to the internal friction and the cohesive force among the powder particles.
By the transformation of Kuno's and Kawakita's equations to the type representing -dε_n/dn with the term of porosity, tapping constants k₁ and b(1-a)/a are obtained, respectively. These constants have the similar property as parameter p that they decrease with the increase of the internal friction and the cohesive force among the particles in fine powders.