USP39-701 崩解时限.pdfVIP

Accessed from 10.6.1.1 by Choay on Sun Feb 26 22:12:12 EST 2017 USP 39 Physical Tests / á701? Disintegration 537 Method Ensure that the reference volume and the calibration volume have been determined for the gas pycnometer by an appropri- ate calibration procedure. The test gas is helium, unless another gas is specified in the individual monograph. The temperature of the gas pycnometer should be between 15° and 30° and should not vary by more than 2° during the course of the meas- urement. Load the test cell with the substance under examination that has been prepared according to the individual mono- graph. Where á699D? is indicated, dry the substance under examination as directed for Loss on drying in the monograph unless other drying conditions are specified in the monograph Density of solids test. Where á699U? is indicated, the substance under examination is used without drying. Use a quantity of powder recommended in the operating manual for the pycnometer. Seal the test cell in the pycnometer, and purge the pycnometer system with the test gas according to the procedure given in the manufacturers operating instructions. If the sample must be degassed under vacuum, follow the recommendations in the individual monographs and the instructions in the operating manual for the pycnometer. The measurement sequence above describes the procedure for the gas pycnometer shown in Figure 1. If the pycnometer differs in operation or in construction from the one shown in Figure 1, follow the operating procedure given in the manual for the pycnometer. Repeat the measurement sequence for the same powder sample until consecutive measurements of the sample volume, Vs, agree to within 0.2%. Unload the test cell and measure the final powder weight, w. Calculate the pycnometr