Metrohm 860 KF Thermoprep Bedienungsanleitung PDF herunterladen (Seite 37)

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5 Performing a determination

860 KF Thermoprep

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5 Performing a determination

Moisture determinations according to the heating method require the

conditioning of the entire tubing system and of the KF titration cell before

a determination can be carried out. Because the sample vials and the sep-

tum seals may contain small amounts of moisture, three to five blank

value determinations must be carried out with sealed, empty vessels.

Solid or liquid samples are weighed out into sample vials, which are then

sealed. We recommend the use of 6.2419.007 sample vials with

6.1448.057 septum seals. The silicone septum of the aluminum cap resists

temperatures of up to 250 °C and has proven itself to be an optimum

solution.

5.1 Conditioning the system

The entire system must be conditioned prior to use, i. e. it must be abso-

lutely water-free. The oven must be heated to the desired working tem-

perature for this purpose. The needle must be inserted into a sealed sam-

ple vessel (conditioning vessel) in order to flush the entire tubing system

with the carrier gas. The gas supply is thus connected with the heating

tube.

5.1.1 Preparing the KF titration cell

Filling the KF titration cell

The KF titration cell must remain filled with conditioned working medium

when not in use. The working medium must be replaced from time to

time, even though the sample is not transferred into the working medium

during the heating-out process.

Prepare the KF titration cell as follows:

Fill the KF titration cell with working medium. We recommend

approximately 150 mL of working medium when using a Coulometer

cell and approximately 35 mL with a volumetric KF titration cell. The

shaft of the heating tube should, however, not be immersed.

Align the tip of the heating tube against the vessel wall.

Switch on the stirrer. Set the stirring rate to high.

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Metrohm 860 KF Thermoprep Bedienungsanleitung Seite 37