10% so2

[homer]

I must be doing something wrong, how do you make a 10% solution of SO2? bk

 

[Runningwolf]

The solution is made by adding sufficient water to 100 grams of Potassium Metabisulphite to bring the total volume to precisely 1 Liter. Store this solution in a tightly sealed clean glass container.

I personally do not do this and I goggled the information to get this.

 

[whackfol]

What's suggested is a 10% solution of K2S2O5. The SO2 percentage is 5.7%. The answer is probably what you were seeking. I only point it out to caution against loose terminology. Either can be used. Just like NaOH strengths for titrations. You just need the correct formula.

 

[homer]

This is were things get fuzzy to me;
To make a solution of 10% So2 you would have to know how much So2 in you NaSo2 your starting with. Why do the mix Potassium or Sodium with So2?

Why are there always two numbers on the charts for So2 additions... 5 PPM and 8 PPM? Do some wines takes 5 PPM and others take 8 PPM? bk

 

[GreginND]

There is no such thing as NaSO2.

Metabisulfite is S2O5(-2) . . . it has a -2 negative charge. Thus it has to have a cation to balance the charge. That there are either two K(+) or Na(+) ions are associated with it.

S2O5(-2) reacts with water under acidic conditions to form SO2.

The amount of free SO2 depends on the concentration of metabisulfite and the pH of the solution.

Generally 5 ppm SO2 is what is desired for red wines and 8 ppm SO2 for white wines. White wines are more delicate and oxidation prone and they need more protection.

 

[homer]

Maybe that's were I'm going wrong, I didn't know you could buy Metabisulfite without Potassium or Sodium added to it. The info about the differance of PPM in white's verses red's clears up one of my mysteries, thank you. bk

 

[sour_grapes]

Maybe that's were I'm going wrong, I didn't know you could buy Metabisulfite without Potassium or Sodium added to it.

You can't. He was just explaining why there are two K (or Na) atoms in each potassium (or sodium) metabisulfite molecule, as opposed to the formula you wrote. I.e., It is only K2S2O5 you can only buy. Metabisulfite by itself would not be a stable molecule.

 

[whackfol]

I think this thread is clouding the topic. My suggestion is to read Ben Rotter's article on SO2 on his web site: brsquared.org.

For instance the 5 ppm and 8 ppm red/white suggestion sounds like the .5 and .8 ppm of molecular SO2 mentioned in his article and other charts. Once you settle on your required level you can calculate, or look up, the amount of free SO2 needed to protect your wine for every pH. I think the table is required because molecular SO2 is not easily measurable. You can measure FSO2 and TSO2.