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a glass vessel of specific shape and volume that is used for measuring the density of substances in the gaseous, liquid, and solid states.
Density is measured with a pycnometer by weighing a substance, usually in the liquid state, that is placed in the device and fills the pycnometer to a mark on its neck or to the upper edge of a capillary tube, corresponding to the nominal volume of the pycnometer. The measurement of volume is considerably simplified if the pycnometer has a scale rather than a single mark. Pycnometers with a side capillary tube in which the stopper is the body of a thermometer are particularly convenient in operation. The density of solids is determined by placing them in a pycnometer with a liquid. Pycnometers of special shape, such as spherical, are used to measure the density of gases.
The major advantages of the pycnometric method for the determination of density are high accuracy of measurement (to 10-5 g/cm3), the possibility of using small quantities of material (0.5 to 100 cm3), the small area of free surface of the liquid in the pycnometer (which virtually eliminates evaporation of the liquid and absorption of moisture from the air), and the separation of the operations of thermostatic control and subsequent weighing.
REFERENCESIzmerenie massy, ob”ema i plotnosti. Moscow, 1972.
GOST 7465–67: Piknometry stekliannye.
GOST 11723–66: Piknometry dlia opredeleniia plotnosti gaza.
S. S. KIVILIS