Metrohm 797 VA Computrace - Manual (Page 31)

2.3 Multi-Mode Electrode (MME)
797 VA Computrace / Hardware-Manual 8.797.8001EN
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2 Draw up mercury
• Attach needle 90 to syringe 89.
• Draw up 6 mL ultra pure mercury slowly and carefully using syringe.
3 Add mercury to MME
• Lower syringe needle 90 into the top opening of the MME 21 between
sealing ring 84 and sealing needle 75.
• Expel mercury slowly and carefully from the syringe to allow it to flow into
the Hg reservoir 81.
The Hg reservoir 81 must never be filled more than 2 / 3 full with mercu-
ry.
2.3.3 Mounting the capillary
The glass capillaries 87 for the Multi-Mode Electrode 21 are supplied separately in a
protective plastic package. After they have been unpacked, avoid any contact whatso-
ever with the sensitive capillary tip. The capillary is mounted in the MME filled with
mercury (as described in section 2.3.2) as follows:
1 Insert retaining nut
• Screw retaining nut 86 into screw thread 82 until a slight resistance is noti-
ceable (on no account screw in retaining nut fully!).
2 Insert capillary
• Cut open plastic package containing the glass capillary 87 on the side of
the large capillary opening using scissors (do not tear open), leave capillary
in the package.
• Insert glass capillary directly from its protective plastic package through the
retaining nut 86 into the sealing ring 84 and push in as far as it will go.
3 Tighten retaining nut
• Firmly tighten retaining nut 86 by hand (do not use a tool). The glass
capillary should then be centered in the opening of the retaining nut.
• If this is not the case, undo retaining nut by one full turn and then retighten
by hand. When tightening, move glass capillary in a circle so that it is cen-
tered in the feed-through of the retaining nut.
2.3.4 Filling capillary without vacuum
The glass capillary 87 can normally be filled with mercury by the method described
here without vacuum. However, if difficulties regarding stability or reproducibility arise
with a capillary filled in this manner, try to fill the capillaries by the alternative method
with vacuum (section 2.3.5). To fill the mounted glass capillary (section 2.3.3) with Hg
without vacuum, proceed as follows: