Hanna Instruments HI 84100 - Manual (Page 7)

7
PRINCIPLE OF OPERATION
The HI 84100 determines the free and total sulphur dioxide concentration in wine using the Ripper
method. Execees iodide added to the wine sample reacts with iodate introduced by the titrant to
produce iodine in situ.
IO
3
- + 5I- + 6H
+ → 3I
2
+ 3H
2
O
The iodine produced in the sample then reacts with sulphur dioxide in the wine according to the redox
reaction below:
H
2
SO
3
+ I
2
→ H
2
SO
4
+ 2HI
The HI 84100 utilizes an ORP electrode to monitor the above redox titration. The integrated
algorithm detects the equivalence point associated with reaction completion. The volume of titrant
required to reach the equivalence point is used, along with the titrant concentration, to calculate the
sulphur dioxide concentration in the wine sample.
18
FUSE REPLACEMENT
To change the fuse follow next steps:
• Disconnect the power cord from the rear panel of
the instrument.
• Pull out the fuse holder located near the power cord
connector.
• Replace the fuse with a similar one.
• Push the fuse holder with the fuse in the appropriate
place.
PUMP TUBE REPLACEMENT
Follow the step below to safely remove the paristaltic pump tubing:
• Detach the old tube system from the reagent bottle.
• Purge the pump to remove any residual titrant from the
tubing.
• Grasp one fixing ring of the peristaltic pump tube.
• Detach tubing from pump housing.
• Remove the other side of the tube.
Follow the step below to mount new peristaltic pump tubing:
• Position one peristaltic pump fixing ring on its location.
• Stretch the tube over the peristaltic pump cylinders.
• Fix the second pump fixing ring on its location.
• Attach the tube to the reagent bottle.
Note: Purge the peristaltic pump until drops of reagent appears on the dosing tip by pressing the
PURGE button.