Metrohm 757 VA Computrace - Manual (Page 34)

3 Installation
757 VA Computrace – Hardware
30
3.3.6 Storing the MME
On completion of the measurements, the MME is stored in the 757 VA Computrace
Stand so that the tip of the glass capillary 88 is immersed in pure water (or in the
solvent used). This prevents blockage of the capillary by crystallized salts.
An electrode treated in this manner can be taken out of the 757 VA Computrace
Stand after a few hours and stored in air for a lengthy period without suffering any
damage. Always store the MME so that the glass capillary 88 is horizontal (see Fig.
11-3).
3.3.7 Replenishing the mercury (without changing capillary)
The multi-mode electrode 17 can also be refilled with mercury without having to re-
move the glass capillary 88.
1 Dismantle multi-mode electrode
• Unscrew FEP tubing 30 and 38 from the MME. Disconnect electrode
cable 16 from the MME.
• Take multi-mode electrode 17 out of the measuring head 20 and tap the
MME gently to knock off any mercury drops on the glass capillary into the
measuring vessel.
• Place multi-mode electrode 17 horizontally in the electrode holder 93
(see Fig. 11-3). The slotted screw 80 is now at the top.
2 Replenish mercury
• Unscrew slotted screw 80 using a suitable coin. If the slotted screw 80
can not be loosened by hand, screw on locking ring 74 and pull out of
the MME.
• Draw up mercury using the syringe 90 with attached needle 91 and expel
into the Hg reservoir 82.
The Hg reservoir 82 must never be filled more than 2 /
3
full with mer-
cury.
• Reinsert slotted screw 80 into screw thread 79 and screw flush to surface
using a suitable coin (this action may expel a few drops of mercury from
glass capillary 88).
Do not turn so tightly that the cemented-in steel threaded ring 79
becomes loose and hence jeopardizes the tightness and safety of the
MME!