# Sulfite Calculator Formula (w/curr SO2, pH, Temp, etc)?



## we5inelgr (Sep 9, 2017)

Hi all,

Does anyone know what the formula (the actual calculation) is behind this:

Sulfite Calculator

I'm looking for the actual formula for use offline.

I have the one where you plug in the desired SO2 level, and gallons of must/wine...but I'm looking for this more complete formula that takes into consideration the current SO2 level, pH and temp, etc.

Thanks.


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## NorCal (Sep 10, 2017)

Here is the formula I derived. It shows the calculation at the bottom; gallons x ppm / 156.25 = grams of SO2. The target ppm needed is based on the chart to the right.


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## we5inelgr (Sep 11, 2017)

Thanks for this info NorCal!

Regarding 156.25. Is that a constant? If so, what's it in relation to or what does it represent?

Also, what if (for example) the starting must/wine has say...10 ppm SO2. How do you work that (existing SO2) into the equation? Simply subtract it from your target of 50 ppm needed? So in this example, it would be 5 x 40 / 156.25 = 1.28 g. Is that how it would work?


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## GreenEnvy22 (Sep 11, 2017)

I have different formulas I use:

Imperial (gallons): =(B5*3.785*(B3-B2))/(1000*0.576)

Metric (Liters): =(E5*(E3-E2))/(1000*0.576)

Where:
B2/E2 = current free SO2 number
B3/E3 = desired free SO2 number
B5/E5 = volume of wine/juice

Yields a similar number to Norcals formula, but not exactly the same. Mine yields 1.64g, his 1.60. Neither of these take into account acidity which can affect the numbers but so little I don't bother.


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## we5inelgr (Sep 12, 2017)

Ok, I found the formula they use _(assuming Gallons and not Liters and using Sulfite Powder)_:

((NetSO2 difference * volume must_wine / 0.57 / 1000) * 3.79 * 0.035) * 28.3495

Now, what shows up down in the "Notes" section is the recommended level of free SO2 based on the type of wine, molecular SO2, pH, and adjustment factor the user entered...is based on this equation _(assuming F and not C for temp)_:

((percentAdjust / 100) + 1) * (desiredMolSO2 * (1 + (10^(WinepH - (1.92 + ((OHbyVolume - 10) * 0.02) + (((WineTemp - 32) * 5 / 9) - 20) * 0.031)))))

_If no Alcohol by Volume is given, then 13.8 is assumed.
If no Percent Adjust is given, then 0 (zero) is assumed.
If no desired molecular SO2 is given, then 0.5 is assumed for Red's and 0.8 for Whites._


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