25mL Specific Gravity Bottle w/Ground Glass Stopper
by United Scientific

Sometimes referred to as a pyknometer or a pycnometer, which comes from the Greek word for “dense”, a specific gravity bottle is something that is used to determine the density of a liquid. Made of glass, the uncalibrated bottles have a close-fitting ground glass stopper which features a capillary tube in the middle to allow any air bubbles to escape.

It helps to facilitate the accurate measurement of a density, which can then be referenced to an appropriate working fluid, such as water or mercury, using an analytical balance. From those measurements, one can then calculate what the relative density of the liquid is.