The Jolly balance is an instrument for determining

specific gravities Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

. Invented by the German physicist

Philipp von Jolly Johann Philipp Gustav von Jolly (26 September 1809 – 24 December 1884) was a German experimental physicist. He measured gravitational acceleration with precision weights and also worked on osmosis. He also designed several tools like the Jolly ...

in 1864, it consists of a

spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a he ...

fastened at the top to a movable arm. At the lower end, the spring is provided with two small pans, one suspended beneath the other. The lower pan is kept immersed to the same depth in water, while the other one hangs in the air. On the upright stand behind the spring is a mirror on which is engraved or painted a scale of equal parts. The specific gravity of an object, typically a

solid Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...

, is determined by noting how much the spring lengthens when the object is resting in the upper pan in air (

w

), and then when the object is moved to the lower pan and immersed in water (

w'

). The specific gravity is

\frac

Notes

References

* Weighing instruments {{Physics-stub

See also

Notes

References