Density Measurement - kruss K11 MK3 User Manual

Measuring principles
Advantages of the ring method
Many international standards for surface and interfacial tension measurements still
•
base upon the ring method.
• Many values in the literature have been obtained with the ring method. This means
that in many cases the ring method should be preferred for comparison purposes.
• The wetted length of the ring exceeds that of the plate by the factor 3. This leads to
a higher force on the force sensor and accordingly to a better accuracy. This effect
doesn't influence the results of surface tension measurements, but small interfacial
tensions can be carried out more accurately with the ring method.
Some substances, e.g. cationic surfactants, show poor wetting properties on
•
platinum. In such cases the surface line between a ring and the liquid is more even
than that of a plate.
15.2

Density measurement

The K11 provides an option for determining the density of liquids. If you need the
density of the liquid(s) for the ring method you do not have to use a different
instrument. In order to determine densities a density determination set is required.
The experiment bases on the fact that as a result of the buoyancy of a solid in a liquid
the measured weight in a liquid is less than that measured in air. The mass of the
volume of liquid displaced by the measuring probe corresponds to the difference in
weight (Archimedes' principle). If the density of the measuring probe is known then the
density of the liquid can be obtained by differential weighing.
The equation for the calculation is:
ρ ρ
=
L MK
= density of liquid; ρ
(ρ
L
probe in air; G
−
G G
⋅
MKA MKL
.
G
MKA
= density of measuring probe; G
MP
= weight of the measuring probe in the liquid).
MPL
page 103
= weight of measuring
MPA