Mettler Toledo InPro 6950 Serie Bedienungsanleitung Seite 39

InPro 6950 Series 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
gases 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 3 value in %)
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 / 2023 METTLER TOLEDO
Printed in Switzerland
Sensor 12 mm
2
Solubility at 20 °C
(68 °F) and 760 mm Hg
9.2 mg O / l
2
2 mg O / l
2
21.9 mg O / l
2
39
InPro 6950
52 206 137 F