The mass of an object divided by its volume is its density (g/cm3). The result is called the envelope density (sometimes the bulk density) when the object’s volume is determined as if a thin film surrounded it and blocked access to pores in the object. When all pores are open and freely accessible so that they can be excluded from the volume measurement, the result is termed the absolute density (sometimes the skeletal, true, or real density). The two densities are equal when the object is nonporous but they are different when the object is porous. Micromeritics’ GeoPyc® 1360 measures envelope density. The Micromeritics AccuPyc 1330 measures absolute density.
The GeoPyc determines the volumetric displacement of a free flowing, dry medium composed of small, rigid spheres — called DryFlo® — by the object being tested. DryFlo® conforms to external features but does not penetrate pores, making it possible to analyze irregularly-shaped samples and samples comprised of multiple pieces (as small as 2 mm).
The use of a dry medium makes the method different from other current procedures. The first of these other procedures, designated Method A1 , seals off the pores in a porous object by dipping the object in molten wax. The envelope density is then calculated from the sample dry weight, the wax-coated weight in air, and the wax-coated weight suspended in water. The second, designated Method B2 , submerges the test object in a pool of mercury and measures the displaced mercury volume. Mercury, being a non-wetting liquid, does not enter into pores under low pressures. Method C3 does not seal off the pores but instead seeks their volume. It requires the object to be dried thoroughly, weighed, boiled in water to remove air from the pores, cooled in water to fill the pores, and then superficially dried. The difference in object weight when dry and when the pores are filled permits calculating the volume of the pores and, from that and the absolute density, the envelope density.
The mass of an object divided by its volume is its density (g/cm3). The result is called the envelope density (sometimes the bulk density) when the object’s volume is determined as if a thin film surrounded it and blocked access to pores in the object. When all pores are open and freely accessible so that they can be excluded from the volume measurement, the result is termed the absolute density (sometimes the skeletal, true, or real density). The two densities are equal when the object is nonporous but they are different when the object is porous. Micromeritics’ GeoPyc® 1360 measures envelope density. The Micromeritics AccuPyc 1330 measures absolute density.
The GeoPyc determines the volumetric displacement of a free flowing, dry medium composed of small, rigid spheres — called DryFlo® — by the object being tested. DryFlo® conforms to external features but does not penetrate pores, making it possible to analyze irregularly-shaped samples and samples comprised of multiple pieces (as small as 2 mm).
The use of a dry medium makes the method different from other current procedures. The first of these other procedures, designated Method A1 , seals off the pores in a porous object by dipping the object in molten wax. The envelope density is then calculated from the sample dry weight, the wax-coated weight in air, and the wax-coated weight suspended in water. The second, designated Method B2 , submerges the test object in a pool of mercury and measures the displaced mercury volume. Mercury, being a non-wetting liquid, does not enter into pores under low pressures. Method C3 does not seal off the pores but instead seeks their volume. It requires the object to be dried thoroughly, weighed, boiled in water to remove air from the pores, cooled in water to fill the pores, and then superficially dried. The difference in object weight when dry and when the pores are filled permits calculating the volume of the pores and, from that and the absolute density, the envelope density.
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