Sulfite Addition Measurements

[joea132]

This is something that's been bothering me for a while now and I have a feeling it's because I'm missing something very obvious. So at the risk of sounding stupid:

If you go to http://www.winemakermag.com/guide/sulfite, it wants to know sulfite additions in Mg/L. My resources all express sulfite levels in PPM. What is the conversion factor, or is it completely unrelated.

I am disappointed to say I tutored chemistry years ago and for the life of me I can't figure this out!

 

[ibglowin]

No conversion needed. ppm and mg/l are the same. If you convert one liter into ml (milliliter), you get 1000 ml. If you assume one ml weighs one gram (water), then one ml = one gram = 1000 mg. Therefore one lit = 1000 g = 1000 * 1000 mg = one million mg.

Therefore one mg/l = 1 mg / 1 million mg = 1 ppm

 

[joea132]

And there you have it. Thanks!

 

[hector]

I took a look at the Calculator which "joea132" mentioned and gave some Data as input to see the Result assuming that it is the first time of adding Sulfite . So , the current amount of free SO2 was 0 mg/lit .

As far as I know , it is assumed that by the first time of adding Sulfite , the half would be bound and the remaining half would be as free SO2 . So , if I would like to have for example 62 mg/lit free SO2 , I should add 124 mg/lit SO2 to the Must .

But , the Calcualtor recommended to add 62 mg/lit SO2 !

Is that right ?!

Hector

 

[BobF]

hector - Your thinking is correct about "immediate" binding. A lot of the lit recommends upping the initial calculated dose by 50%.

I do my early additions by rule of thumb, later testing and adjusting more accurately.

 

[ibglowin]

There is no immediate and automatic binding of SO2 that makes the addition only 57% free. Its just simple math.

The formula for K-Meta is K2S2O5. The molecular weight is 222. Upon dissolution in water or wine it will break down into 2 molecules of SO2 for each molecule of K2S2O5. The molecular weight of SO2 is 64. Since there are two molecules you have 64 x 2 =128.

128/222 = 57.7% by weight of free SO2.

 

[Lurker]

You guys are getting too deep for me. I add to get about 50 ppm until ready to bottle, then I add or not to achieve about 25-30 ppm. I say thank you to my SC 100 each time I check it.

 

[BobF]

There is no immediate and automatic binding of SO2 that makes the addition only 57% free. Its just simple math.

The formula for K-Meta is K2S2O5. The molecular weight is 222. Upon dissolution in water or wine it will break down into 2 molecules of SO2 for each molecule of K2S2O5. The molecular weight of SO2 is 64. Since there are two molecules you have 64 x 2 =128.

128/222 = 57.7% by weight of free SO2.

True, but a different subject

 

[ibglowin]

I guess I don't understand your reply at all.

Hector said "As far as I know , it is assumed that by the first time of adding Sulfite , the half would be bound and the remaining half would be as free SO2"

and you agreed with him and said "Your thinking is correct about "immediate" binding" as if you agree that you somehow lose 50% magically....

True, but a different subject

 

[hector]

There is no immediate and automatic binding of SO2 that makes the addition only 57% free. Its just simple math.

The formula for K-Meta is K2S2O5. The molecular weight is 222. Upon dissolution in water or wine it will break down into 2 molecules of SO2 for each molecule of K2S2O5. The molecular weight of SO2 is 64. Since there are two molecules you have 64 x 2 =128.

128/222 = 57.7% by weight of free SO2.

I've read about it in many Articles and Homepages and they all say that when small additions of sulfur dioxide are added to young wines that contain small or no amounts of sulfur dioxide , about half the added sulfur dioxide quickly becomes bound and is no longer available as free sulfur dioxide .

Please take a look at the Attachment which "Tom" has provided with the following Thread :

http://www.winemakingtalk.com/forum/showthread.php?t=4915

( See page no. 35 & 39 )

What you said about the dissociation of K-Meta is theoretically true , but in Practice the yield percentage of

SO2 has been always 30-50 % .

Hector

 

[BobF]

I guess I don't understand your reply at all.

Hector said "As far as I know , it is assumed that by the first time of adding Sulfite , the half would be bound and the remaining half would be as free SO2"

and you agreed with him and said "Your thinking is correct about "immediate" binding" as if you agree that you somehow lose 50% magically....

Magic has nothing to do with it. The initial SO2 addition is being added to a must/wine that is full of compounds that readily bind to SO2. The binding isn't exactly immediate, but it does happen quickly.

Future SO2 additions have less and less compounds that aren't already bound to SO2, so more of these additions are contributing to FREE SO2.

I find http://brsquared.org/wine/Articles/SO2/SO2.htm to be the best overall write-up on SO2 I've found yet.

The entire article is worth reading; 5.5 and 13.3 are specific to the subject at hand.

Note that additions discussed in the article have already accounted for the fact that k-meta powder (and other forms) aren't 100% SO2. The calculations and discussions are in the context of actual SO2 quantities being added.

 

[grapenutz]

# of gal x .0067 x desired ppm = grams of KMBS to add to batch.

- if it is the first addition, all kmbs will bind up within a day at most (quicker if full of lees or solids)

- never add during fermentation unless you are freezing the batch for residual sugar
• so2 will stress yeast and release H2S and your batch may smell like rotten eggs!

- always add based on p.h
• if no meter is available it will be tough (try hitting 75ppm right before bottling because 20-50 ppm may be lost within the first few weeks)

Hope this helps! Anyone please correct me if i'm wrong.
Cheers!

 

[whackfol]

I realize this thread goes back a year. I got confused reading it when it appeared the percentage SO2 in K2S2O5 seemed to morph into the discussion of free versus bound SO2 post addition. Grapezutz formula and all of the calculators I have seen for SO2 additions do not make an allowance for bound SO2 and I'm not sure there is any study based predictor of the amount which will or may bind. My experience tells me that a high percentage of SO2 binds in the initial addition. From then on, I find the storage container has more to do with my maintaining my FSO2 levels. Interestingly, my VCT's require greater additions than my barrels. I guess it means either, I'm not that good at sealing the VCT or they aren't as good as I'd like. I do flush with argon before I seal and do a pretty good job sealing and maintaining the lid on the wine.

 

[grapenutz]

I've read that the oxide layer of stainless steel can pop those kmbs molecules apart (same with esters and terpenes! Ever notice how great it smells after being sealed up for a few weeks?) I spend less kmbs on a topped off PVC tank (if done correctly) than a stainless.