Metrohm 763 PVC Thermomat Manual - Manual (Page 74)

4.6 Determinations
763 PVC Thermomat
67
• When the instrument is not in use always close the openings
with stoppers.
2 Measuring vessels and accessories
• After the contents have been discarded clean used meas-
uring vessels 44 several times with alcohol and distilled water
(do not use acetone!).
• Rinse the measuring vessel cover 55 complete with elec-
trodes 28 28 and PTFE tube 27 27 several times with distilled water
and acetone. If necessary, remove the protective ring 29 29 for
better access to the electrodes 28 28 (see Fig. 4).
• Rinse the connecting tubing 33 between reaction vessel and
measuring vessel several times with distilled water and ace-
tone.
3 Reaction vessels and accessories
• It is recommended to use new reaction vessels 11 and gas
inlet tubes 32 32 for each determination. Blow out new reaction
vessels with nitrogen.
• Used and not too strongly contaminated reaction vessels and
gas inlet tubes can be cleaned by immersion in boiling RBS
solution for 1 h or a similar laboratory flushing agent. They
must then be thoroughly rinsed with distilled water and ace-
tone.
RBS attacks glass. Reaction vessels and gas inlet tubes
therefore cannot be cleaned ad infinitum.
• Remove the gas inlet tube 32 32 from the reaction vessel
cover 22 and rinse it several times with distilled water and
acetone. Dry the cover at 80 °C in a drying oven.
Reaction vessel covers which have not been dried properly
can falsify the results of the following determinations.
Prepare measuring vessels
The cleaned measuring vessels must always be prepared as follows
before the start of a determination (see Fig. 4):
1 Fill measuring vessels
• Fill each cleaned measuring vessel 44 with 60 mL distilled
water. For analysis times >24 h more than 60 mL distilled
water must be added to take the evaporation losses of ap-
prox. 7 mL/d into account and to ensure that the electrodes
remain adequately immersed.