The effect of grinding in an agate cetrifugal ball mill on the physicochemical properties of form A of chloramphenicol palmitate (CPP) was studied by means of X-ray diffractometry, differential scanning calorimetry (DSC) and infrared (IR) spectrophotometry.
The peak intensities of X-ray diffraction profiles of form A decreased with increasing grinding time, and a part of form A converted to a noncrystalline solid. The crystallinity of form A ground for 1-10h was about 50% by means of Hermans' method.
The melting point and heat of fusion of form A ground for 1-10h decreased about 3°C and about 11.2kJmol^-1, respectively, compared with those of intact form A. The solubility of form A ground for 10h was about twice higher than that of the intact form A.
The IR spectra of ground form A suggested that the amputation of the intermolecular hydrogen bond between the carbonyl group of the amido and the hydroxyl group in the crystal structure of form A was caused by mechanical stress during grinding, and that form A converted to a noncrystalline state.

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Dust deposition inside of sampling tubes was evaluated using a test system which consisted of a sampling nozzle with a 90° bend, a sampling tube with ten 20-cm glass pipes, an elbow and a dust collector. The deposition test was carried out as a function of suction gas velocity and tube diameter using calcium carbonate (d_p50=3.8μm, C=300mg/m³) as the test dust. The test results showed that 33-68% of the test dust was accumulated, and most of the deposition occurred in the 90° bend of the sampling nozzle.
Grit injection into the 90° bend of the sampling nozzle was tried using large sand particles (d_p50=300μm) as a countermeasure of dust deposition. About 93% of the dust deposited inside of the sampling nozzle could be blown off within four minutes of grit injection. Simultaneous grit injection with dust sampling was also confirmed to be fully efficient.

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The fracture probability of particle (P_f) under impact loading by a blow of a drop weight falling was analyzed based upon the weakest-link model, and was derived as the following equation; P_f=1-exp[-(p/L_a)^2.5]. p is the impact force of action to the particle and was deduced from the Hertz's theory of contact and impact energy of the drop weight. L_a is the mean fracture load of the particle, and the value of L_a measured by slow compression testing was taken into account for the culculation of P_f. The results of P_f calculated by the use of the equation mentioned above was closely related to the experimental data.

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タイ国では, さまざまな粉体関連機器が, 農業, 工業などの幅広い分野で使用されているものの, 学問としての粉体工学は, ほとんどない状態であり, 核となる研究者や企業もほとんどいないのが現状である。これは, タイ国の工学全体が未分化であり, 鉱山学以外では独立した学会組織を持っていないことに因るところが大である。したがって, 粉体工学のように非常に専門化した分野ではなおさらである。
このため, タイ国には先進国の技術や知識の導入を計る団体が多数あるが, なかでも, 泰日経済技術振興会 (TPA) は先進的な役割を果している。TPAは日本の経済援助により, 日本への留学経験を持つ人達を中心に組織された非営利団体であり, セミナー, 翻訳出版, 日本語教育等に精力的に取り組んでいる。粉体工学との関連では, これまでに, 大気汚染と集塵技術に関するセミナーを開いた程度であまり活溌とはいえない。しかし, 今後は固体ハンドリングや空気輸送について, セミナー, 翻訳を手掛けたいと考えている。
いづれにしても, タイ国に粉体工学が定着するかどうかは工業化のスピード, それをとりまく環境の変化などにもよるが, 最も重要なことはタイ国内に核となる研究者グループが形成されるてとであろう。このためには外国からの援助が必要であり, その窓口として, Chulalongkorn 大学や, TPAが一定の役割を果せると思う。

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