Page 13 - Grapevine JanFeb 2022

In The Winery
acid to 666.33 milliliters water to make one
liter. Transfer a portion of this mixture to the
preset squeeze bottle, set at 10 milliliter deliv-
ery, so it is ready for use.
• Purchase the dye indictor because making it is
much too daunting.
• Purchase 30% Hydrogen Peroxide and mix 3.0
milliliters into 97.0 milliliters of distilled water
(this should be ample to cover very high free
SO2’s). Add about 2 drops of 0.01 Normal
Sodium Hydroxide to this fresh stock mix to shift
the pH slightly to the basic side. This will help
the indictor solution to give a vivid “seawater”
green at the beginning of each test and after
the titration is complete. Do not use store pur-
chased hydrogen peroxide from a local pharma-
cy.
Procedure
1. Make sure your apparatus is clean, set up
properly and in good working condition. After
cleaning, rinse all of the lab ware with distilled
water to remove any minerals and residues.
Allow to dry.
2. Make sure the chemicals are readily available
and mixed to the proper concentrations.
3. Fill the 10 ml volumetric burette with 0.01 N.
NaOH and make sure all air bubbles are out of
the stopcock and delivery tip area. Inspect.
4.Standardize the 0.01 N NaOH if not already done
above. This is crucial for good measurement.
5. Rinse the reaction flask with a small amount
(5 milliliters) of the premixed 0.3% (or greater)
hydrogen peroxide (H2O2).
6. To the Hydrogen peroxide reaction flask add the
amount of 0.3% H2O2 (approximately 10 mils)
and 5-6 drops of dye indicator.
7. Attach the reaction flask into the clamp holder
and place the glass bubbler portion back into
the reaction flask.
877-892-5332 The Grapevine • January - February 2022
Grapevine Main Pages GV111221_Layout 1-1 copy.indd 11
8. Select a fresh representative sample of the wine
to be tested that was already collected and
placed in the lab. Using the 20 milliliter volu-
metric pipette transfer exactly 20 milliliters of
wine into the lower boiling flask.
9. Be ready to place the wine sample boiling flask
onto the remaining glassware to complete the
set up.
10. Add 10 milliliters of the 25% phosphoric acid
to the wine sample in the lower boiling flask.
[Be careful with this phosphoric acid since it
may splash onto you or into unwanted areas of
the apparatus. Perhaps hold it away from the
Aeration-Oxidation set up and over a sink.
11. Immediately place the rubber stopper onto the
wine sample boiling flask making the assembly
complete and a “closed system”.
12. Now turn on the vacuum source to vacuum air
through the complete set up. You should see a
“boiling” action in both the wine sample boiling
flask and the reaction flask. This should be vig-
orous but not so vigorous that effluent is being
transferred from one reaction vessel to the next
– only air should be moving through the tubing.
13. Time the operation of the units vacuum for 10
minutes – note the reaction flask should have
turned purple in color in the first minute – if
any Free Sulfur Dioxide is present. Continue to
monitor the test during the timed 10 minute
interval making adjustments to the vacuum
source, if necessary.
14. Turn off the vacuum source after the desired 10
minutes.
15. Disconnect the reaction flask (the one that
turned purple) – from the rest of the lab set up
assembly. This will be done by removing the
bubbler assembly from the unit and rinsing off
any remaining solution on the bubbler tip with a
small amount of distilled water.
16. Turn to your pre-prepared and standardized
0.01 Normal Sodium Hydroxide burette and
Page 11
12/16/21 3:29 PM