Metrohm 824 Easy Sample Changer - Manual (Page 55)

8.5 Sample beakers for Karl Fischer titrations
824 Easy Sample Changer, Annex
49
8.4.3 Aspiration tip
The Metrohm 772 Pump Unit with aspiration equipment can be used for
aspirating used sample solutions without any problems. If the sample
solutions contain solids, precipitates (e.g. silver chloride) or sticky sub-
stances then a peristaltic pump such as the Metrohm 772 Pump Unit
must be used, as diaphragm pumps can easily be blocked up or stuck
together by solids.
The 6.1543.170 Aspiration tips can be used with all titration heads with
SGJ9 openings, see above drawing.
Take the chemical resistance of the tubing and connections into ac-
count.
Polyethylene canisters (Metrohm Order. no. 6.1621.000) can be used
as waste canisters for aqueous media.
The 6.1821.000 Aspiration Tube is used with the KFT titration head. It
should always be used as it ensures trouble-free penetration of the
aluminum foil on the KF sample vessels.
8.5 Sample beakers for Karl Fischer titrations
For Karl Fischer titrations the
measured-out sample is placed in a
6.1432.210 Sample Beaker together
with a 6.1903.010 Stirrer Bar. The
beaker is then covered centrally
with 6.2820.000 Aluminum foil which
is kept in place by the foil holder.
Fig. 26 Karl Fischer sample beaker
During the method sequence the lift with the titration head is moved to
the working position. The aspiration tube should be the first object to
penetrate the Al foil.
Attention
Always attach the 6.1821.000 Aspiration Tube to the KFT titration
head, even when you do not intend to aspirate sample solutions. The
aspiration tube is used to penetrate the Al foil.
Use only 6.2820.000 Al Foil as this has a defined thickness
(0.010 mm).
Sample
beaker
Al foil
Foil holder
6.2037.040