Mettler Toledo InPro 6850i Bedienungsanleitung Seite 39

InPro 6850i / 6900i / 6950i O
The solubility factor is strongly influenced not only by
the temperature but also by the composition of the
solution:
Medium, saturated with air
Water
4 mol/l KCI
50 % Methanol-water
Although the solubilities vary widely, the oxygen elec-
trode gives the same reading in all three solutions.
Thus, determination of the oxygen concentration is
only possible with constant and known solubility fac-
tors "a".
Solubility may be determined by a Winkler titration or
the method developed by Käppeli and Fiechter.
Measurement in gases
The concentration of oxygen when measuring in gas-
es is always given as a proportion by volume of the
gas composition. Common units are % (by vol.)
ppm (by vol.).
They can simply be converted from one unit of mea-
surement to the other.
Example:
The percent by volume of the composition of air is
generally known. For example, air contains 20.95 %
oxygen. This corresponds to 209,500 ppm (by vol.).
(Conversion: ppm value = 10,000
References
– W.M. Krebs, I.A. Haddad Develp. Ind. Microbio.,
13, 113 (1972)
– H. Bühler, W. Ingold GIT 20, 977 (1976)
– W.M. Krebs, MBAA Techn. Quart. 16, 176 (1975)
– D.P. Lucero, Ana. Chem. 40, 707 (1968)
© 02 / 09 Mettler-Toledo AG
Printed in Switzerland
Sensor 12 / 25 mm
2
Solubility at 20°C (68°F)
and 760 mm Hg
9.2 mg O
2 mg O
21.9 mg O
InPro 6850i, 6900i, 6950i
/l
2
/l
2
/l
2
value in %)
52 206 349
39