Question

How does ripper method work to determine SO2 levels in wine?

What is the redox reaction occuring between SO2 and I2 with the use of starch in the ripper method? How does this method chemically work to find the amount of free and total SO2 in wine?

Answer 1

Here's what I get.

Explanation:

`"SO"_2` in Winemaking

Winemakers add `"SO"_2` to their product to keep it stable.

Some of the `"SO"_2` binds to the various compounds in the wine, and the rest remains unbound (i.e., "free").

The sum of the bound and free `"SO"_2` is the total `"SO"_2`.

The Ripper method is a titration technique for analyzing both the free and total `"SO"_2` in wine.

(a) Determination of free `"SO"_2`

In the titration, a standard solution of iodine reacts with the `"SO"_2`.

`"SO"_2 +"I"_2 + 2"H"_2"O" → "H"_2"SO"_4 + "2HI"`

At the equivalence point, the addition of one more drop of iodine solution causes the starch indicator to form a blue-black complex (you can also use an electrode to detect the equivalence point).

(b) Determination of total `"SO"_2`

The method is the same as above except that you pretreat the sample with a solution of sodium hydroxide.

The `"NaOH"` releases the bound `"SO"_2` as the hydrogen sulfite ion.

The sulfite ion is in equilibrium with the dissolved `"SO"_2`.

`"HSO"_3^"-" ⇌ "H"_2"SO"_3 ⇌ "SO"_2`

Then you perform the titration in the usual way.