A dasymeter was meant initially as a device to demonstrate the buoyant effect of gases like air (as shown in the adjacent pictures). A dasymeter which allows weighing acts as a densimeter used to measure the

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

of gases.

Principle

The Principle of Archimedes permits to derive a formula which does not rely on any information of volume: a sample, the big sphere in the adjacent images, of known mass-density is weighed in vacuum and then immersed into the gas and weighed again. :

\frac   = \frac  \,

(The above formula was taken from the article

buoyancy Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

and still has to be solved for the density of the gas.) From the known mass density of the sample (sphere) and its two weight-values, the mass-density of the gas can be calculated as: :

= \frac   \times

Construction and use

It consists of a thin

sphere A sphere (from Ancient Greek, Greek , ) is a surface (mathematics), surface analogous to the circle, a curve. In solid geometry, a sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...

made of

glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...

, ideally with an average density close to that of the gas to be investigated. This sphere is immersed in the gas and weighed.

History of the dasymeter

The dasymeter was invented in 1650 by

Otto von Guericke Otto von Guericke ( , , ; spelled Gericke until 1666; – ) was a German scientist, inventor, mathematician and physicist. His pioneering scientific work, the development of experimental methods and repeatable demonstrations on the physics of ...

Archimedes Archimedes of Syracuse ( ; ) was an Ancient Greece, Ancient Greek Greek mathematics, mathematician, physicist, engineer, astronomer, and Invention, inventor from the ancient city of Syracuse, Sicily, Syracuse in History of Greek and Hellenis ...

used a pair of scales which he immersed into water to demonstrate the buoyant effect of water. A dasymeter can be seen as a variant of that pair of scales, only immersed into gas.

References

External links

Volume Conversion
Measuring instruments Laboratory equipment Laboratory glassware {{Measurement-stub