Sartorius Cubis Series - Page 77

Calculation Basis for Density Determination
The density determination application is based on the equations:
Rho Density of sample (ρ)
ρ
fl
Density of buoyancy liquid
W
a
Weight of sample in air
W
fl
Weight of sample in liquid (when determining liquid density, buoyancy
and displacement)
Weight of fill medium (for pycnometer)
W
r
Weight of sample and fill medium (for pycnometer)
LA Air buoyancy correction = 0.0012 g/ccm
Buoyancy: Rho = (W
a
*
(ρ
fl
- LA)) / ((W
a
- W
fl
)
*
corr) + LA
Displacement: Rho = (W
a
*
(ρ
fl
- LA)) / (W
fl
*
corr) + LA
When the displacement method is used to correct for buoyancy by means of a wire
(string) suspended in liquid, the factor 1.00000 is used in the calculation as
a factory-set default.
The correction factor Corr is calculated from: Corr = 1 - n
*
d
2
/ D
2
with:
n Number of wires
d Wire diameter (YKD01MS: 0.7 mm)
D Inner diameter of the vessel being used (YKD01MS: 76 mm)
When other vessels or other submersion assemblies are used, this factor can
be changed by modifying the parameters for the density kit.
Density Determination
Cubis MSU User Manual 77