The Stereopycnometer is a manually operated instrument designed to measure the true volume of powders and other solid materials by employing Archimedes' principle of fluid (gas) displacement and the technique of gas expansion. From this volume, density is easily determined by dividing into the weight of the sample. It features a digital display and fine adjustment controls for both pressurization and venting rates. A complete density analysis can be done in as little as a minute.
Gas is used as the displacing fluid since it penetrates the finest pores assuring maximum accuracy. For this reason helium is recommended, since its small atomic dimension enables entry into crevices and pores approaching two Angstrom (10-10m). Its behavior as an ideal gas is also desirable. Other gases such as nitrogen can be used, often with no measurable difference.
The Stereopycnometer comes with a choice of two inter-changeable sample cells used in conjunction with a single reference volume.
A sample is placed in the sample cell and degassed by purging with a flow of dry gas, by vacuum, or by a series of pressurization cycles. The standard analysis is performed by pressurizing the sample cell to approximately 17 psi and recording the value. The selector valve is rotated so the gas expands into the reference or added volume and that lower pressure is recorded. From these two readings, the sample volume can be quickly and accurately calculated.
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