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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[in Japanese]

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