kruss K11 MK3 User Manual page 51

Ring method measurements
Zuidema & Waters (3)
•
calculations on the data measured by Harkins & Jordan. The method is intended for
interfacial tension measurements, but has a larger range of variation than the
correction according to Harkins & Jordan; it should only be used for comparative
measurements with values given in the literature.
Linear (4)
•
older KRÜSS tensiometers and should only be applied when the K11 is used
together with these tensiometers for the same tasks. The following types of
tensiometer are affected: KRÜSS K6, K8, K8451, K8501, K8551, K8600, K8600EE,
K9 and all instruments of the K10 series.
The measured values are multiplied by a factor obtained from the quotients of the
actual surface tension of pure water (72.8 mN/m) and the uncorrected measured
value for water. The linear correction was sufficiently accurate for the less sensitive
force measurement systems but in the meantime it has been replaced by the
correction methods described above.
If the linear correction method is used then the measuring procedure for the ring
method is additionally adapted to suit the methods used with the older
Tensiometers. With modern Tensiometers the film below the ring is stressed
beyond the maximum force and the required maximum force is only measured on
the return movement, i.e. when the stress on the film is relaxed. If the linear
correction is selected then the maximum force will be measured when the film is
being stressed, just as on the older models. Various effects mean that the
maximum measured in this way is slightly too high.
: The two authors of this method carried out interpolation
: This correction has been provided for reasons of compatibility with
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