Hanna Instruments HI 84100 - Manual (Page 5)

5
Wine makers add sulphur dioxide to wine in order to inhibit bacteria and wild yeast, and to serve as
an antioxidant to prevent browning.
A small portion of the free sulphur dioxide, known as molecular SO
2
, is active and responsible for
protecting wine.
The relationship between the amount of SO
2
added and the amount of free SO
2
in wine is complex.
It is clear, however, that the relationship is largely governed by the total SO
2
content of the wine.
The exact relationship between free and bound (total - free) SO
2
will vary from wine to wine.
When SO
2
is added to wine some immediately becomes bound.
The remaining unbound SO
2
is called “free” and is divided in two parts.
The larger, and relatively ineffective free portion is called “bisulphite” (HSO
3
¯).
The smaller portion of the free sulphur dioxide, known as molecular SO
2
, is active and resposible for
protecting wine.
The amount of molecular SO
2
in wine depends on both the level of free SO
2
present as well as the pH.
For instance, at pH 3.2, the amount of free SO
2
for 0.8 ppm molecular SO
2
is 22 ppm. At pH 3.5,
you will need 43 ppm free - essentially double.
Free SO
2
concentration (ppm) for 0.8 ppm molecular SO
2
:
In most bulk storage and at bottling situation 0.8 ppm molecular SO
2
provides adequate protection
from oxidation and bacterial action (including malolactic).
It is important to remember that the amount of free SO
2
in the wine depends on three things: how
much is added, how much was present before the addition and how much of your addition promptly
becomes bound.
The level at which molecular SO
2
can be detected by the human senses is about 2.0 ppm.
This is also the level which is needed for maximum protection of wine.
This is particularly true in the case of sweet, and most notably, botrytised wines.
The HI 84100 makes it possible to test free or total SO
2
in all the wines including the red, which are
difficult to test with manual methods due to the indistinct color changes associated with traditional
endpoint indication.
SIGNIFICANCE OF USE
H p 0. 3 1. 3 2. 3 3. 3 4. 3 5. 3 6. 3 7. 3 8. 3 9. 3
O S e e r F
2
4 1 8 1 2 2 8 2 5 3 4 4 5 5 9 6 7 8 9 0 1
20
STORAGE PROCEDURE
To minimize clogging and assure a quick response time, the glass bulb and the junction of the
electrode should be kept moist and not allowed to dry out.
Replace the solution in the protective cap with a few drops of HI 70300 Storage Solution or, in its
absence, Filling Solution (HI 7082). Follow the Preparation Procedure before taking measurements.
Note: NEVER STORE THE ELECTRODE IN DISTILLED OR DEIONIZED WATER.
PERIODIC MAINTENANCE
Inspect the electrode and the cable. The cable used for connection to the instrument must be
intact and there must be no points of broken insulation on the cable or cracks on the electrode
stem or bulb. Connectors must be perfectly clean and dry. If any scratches or cracks are present,
replace the electrode. Rinse off any salt deposits with water.
Probe Maintenance
Refill the reference chamber with fresh electrolyte (HI 7082). Allow the electrode to stand
upright for 1 hour. Follow the Storage Procedure above.
CLEANING PROCEDURE
•
Wine deposits Soak in Hanna HI 70635 cleaning solution for 15 minutes
• Wine stains Soak in Hanna HI 70636 cleaning solution for 15 minutes
IMPORTANT: After performing any of the cleaning procedures, rinse the electrode thoroughly
with distilled water, refill the reference chamber with fresh electrolyte and soak the electrode in
HI 70300 Storage Solution for at least 1 hour before taking measurements.
For faster response, unscrew the fill hole screw during measurements.