Development of Karl Fischer Reagents

I-1. Questions & Answers about Karl Fischer Reagents
[Procedures]
a) Solid samples
i) Nitrogen gas (or air) is first passed through a drying tube (filled with
silica gel or phosphorus pentoxide, etc.) and then supplied at a rate of
approximately 300ml/min. to an oven that is maintained at a suitable
temperature for vaporization.
ii) The sample boat is placed in the heating tube and exposed to the flow of
nitrogen gas to ensure that the heating system is free of moisture.
iii) The sample is immediately placed in the sample boat and inserted into
an oven that is maintained at the required temperature.
iv) The vaporized moisture is absorbed into a dehydrated solvent in a
titration flask (or into an electrolyte in an electrolysis cell).
v) The absorbed water is subjected to Karl Fischer titration.
b) Liquid samples, such as lubricating oils
i) Approximately 20ml of a base oil (mineral oil, vacuum pump oil, etc.) is
placed in the heating unit of a moisture vaporization system and heated
to 100-150 � C.
ii) The moisture content of the base oil is totally removed by introducing a
flow of dried nitrogen gas into the moisture vaporization system at the
rate of approximately 300ml/min.
iii) 1-10g of the sample is added to the base oil, which is now free of
moisture.
iv) The vaporized moisture is absorbed into a dehydrated solvent in a
titration flask (or into an electrolyte in an electrolysis cell).
v) The absorbed water is subjected to Karl Fischer titration.
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Measurement unit
Drying tube
Carrier gas
Exhaust vent
Measureme
nt system
Detection electrode
Vaporization unit
Temperature regulation
system
Ribbon heater
Oven
Thermocouple
Blowing tube
Titration solvent or anolyte
Oven
Sample boat
Magnet
Sample injection port
Push rod
Heating tube
Screw lid
Titration flask or electrolysis cell
Drying tube
Carrier gas supply unit
Figure 4: A Moisture Vaporization System (for Solid Samples)
Flowmeter
Nitrogen