Oxygen Partial Pressure - Oxygen Concentration - 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
gen concentration in mg O
determined directly with an electrode.
According to Henry's law the oxygen concentration is
proportional to its partial pressure (PO
CL = 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 on-
ly 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)
© 10/05 Mettler-Toledo GmbH
Printed in Switzerland
Sensor 12/25 mm
2
2
solubility in the solutions. The oxy-
2
• a
2
permeability of the membrane –
/l (CL) cannot therefore be
2
Solubility at
20°C (68°F) and 760 mm Hg
9.2 mg O
2
2 mg O /l
2
21.9 mg O
).
2
/l
/l
2
InPro 6800
52 200 953
35