User manual

6 ALT-A02/PLT-A01-BA-e-1310
ρ =
V
A-B
Determining density of liquids
The density of a liquid is determined with the help of a sinker providing a known
volume [ V ]. The sinker is weighed in air [ A ] as well as in the test liquid [ B ].
According to the Archimedes’ Principle a body immersed in a liquid experiences a
force of buoyancy [ G ]. This force equals the weight force of the liquid displaced by
the volume of the body.
The volume [ V ] of the immersed body equals the volume of the displaced liquid.
G = buoyancy of sinker
Buoyancy of sinker =
Weight of the sinker in air [ A ] - weight of sinker in test liquid [ B ]
From this follows:
ρ = density of sample liquid
A = weight of sinker in air
B = weight of the sinkers in test liquid
V = volume of sinker*
* If the volume of the sinker is unknown, this can be determined by a solid body
density measurement e.g. in water and be calculated as follows.
V = volume of sinker
A = weight of sinker in air
B = weight of sinker in water
ρ
W
= density of water
2.1 Influencing magnitudes and error sources
 Air pressure
 Temperature
 Volume deviation of the sinker
 Surface tension of the liquid
 Air bubbles
 Immersion depth of the sample dish or of the sinker
 Porosity of the solid