New volume measurement for the density determination of weights using a gas pycnometer

摘要

The new volume measurement method by using the expansion of gas pressure is described. Using somegases as a pressure medium an accuracy of about 0.2 percent or better is achieved for density of 1 kg weights made of stainless steel. The new apparatus consists of chamber set for a sample and some expansions, a precise pressure transducer, thermometer, and a vacuum pump. The ideal gas law can be used to measure the volume of weights since the gas is expanded so that the pressure remains below 1 atm. The volume of a sample chamber is calibrated by filling gas near atmosphere pressure into vacant sample chamber and by expanding the gas of sample chamber into vacant expansion chambers. A standard volume is used for calibration of chamber set for sample and expansion. The volume of weights can easily be measured with this new apparatus compared with hydrostatic weighing method by Archimedes' principle in time and procedure for measurement.