User manual

Determining density of liquids
The density of a fluid 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 sample fluid [ B ].
According to the Archimedes’ Principle a body immersed in a fluid experiences a
force of buoyancy. [ G ]. This force equals the weight force of the fluid displaced by
the volume of the body.
The volume [ V ] of the immersed body equals the volume of the displaced fluid.
G = buoyancy of sinker
Buoyancy of sinker =
Weight of the sinker in air [ A ] - weight sinker in sample liquid [ B ]
From this follows:
ρ =
V
A
-
B
ρ = density of sample fluid
A = weight of sinker in air
B = weight of sinker in sample fluid
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
Ö Air pressure
Ö temperature
Ö Volume deviance of the sinker (± 0.005 cm
3
)
Ö Surface tension of the liquid
Ö Air bubbles
Ö Immersion depth of the sample dish of sinker
Ö Porosity of the solid
6 ABS-A02-BA-e-1010