Stereometer
A stereometer (Greek) is an apparatus for determining the volume of powdery bodies filled with solid matter .
functionality
The stereometer from Say consists of a glass vessel A, the evenly ground edge of which can be hermetically sealed by a glass plate; it continues downwards into an open glass tube with a graduation, the volume of which between two graduation lines is precisely known. If the tube, while A is open, is immersed in a standing vessel filled with mercury up to the zero point o of the division and the glass plate is placed on it, a certain volume of air v is blocked, the pressure of which is indicated by the prevailing barometer reading b.
If one now pulls the vessel A upwards, the air contained in it expands by the volume w to be read from the graduation, its pressure becomes lower, and the like. the outer one lifts a column of mercury h into the tube. According to Mariott's law one now has the proportion v + w: v = b: bh, from which, since w, b and h are known, v can be calculated. If the same experiment is repeated after the powdery body, the volume of which x is to be determined, has been placed in the vessel A, the volume of the air shut off when the tube is immersed to zero is vx.
If one now raises the tube again until the volume has increased by w, and if the mercury column h 'is raised, then one can find the volume x from the proportion v-x + w: vx = b: bh'. The specific weight of the powder is obtained by dividing the absolute weight of the powder (in grams) by its volume (in cubic centimeters) .
The Kopp and Regnault volumeters are based on the same principle and have the same purpose as the stereometer.
