Oxygen Partial Pressure - Oxygen Concentration; Inpro 6800 - Mettler Toledo InPro 6800 Serie Instructions D'utilisation

InPro 6800 Series O
10.7 Oxygen partial pressure –
oxygen concentration
The electrode current depends on the oxygen partial
pressure and the O
but not on the O
concentration in mg O
determined directly with an electrode.
According to Henry's law the oxygen concentration is
proportional to its partial pressure (PO
a = solubility factor
If "a" is constant, the oxygen concentration can be
determined by means of the electrode. This applies at
constant temperature and with dilute aqueous
solutions such as drinking-water.
The solubility factor is strongly influenced not only by
the temperature but also by the composition of the
solution:
Medium, sat. with air
Water
4 mol/l KCI
50 % Methanol-water
Although the solubilities vary widely, the oxygen
electrode gives the same reading in all three solutions.
Thus, determination of the oxygen concentration is
only possible with constant and known solubility
factors "a".
Solubility may be determined by a Winkler titration or
the method developed by Käppeli and Fiechter.
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)
© 12 / 2018 Mettler-Toledo GmbH
Printed in Switzerland
Sensor 12/25 mm
2
solubility in the solutions. The oxygen
2
CL pO
2
permeability of the membrane –
2
/l (CL) cannot therefore be
2
a
Solubility at
20 °C (68 °F) and 760 mm Hg
9.2 mg O
2 mg O
2
21.9 mg O
).
2
/l
2
/l
/l
2

InPro 6800

52 200 953 B
39