A classmate of yours, an inexperienced Winemaker in a small but very friendly la

Question

A classmate of yours, an inexperienced Winemaker in a small but very friendly landlocked Balkan country asks for your advice on SO2. She has a Vranec with the characteristics below. It is from the 2016 vintage and is finished MLF. She knows that to protect the wine from microbial assault she should maintain a MSO2 of at least 0.80 mg/L.

Volume

3,648

L

pH

3.24

SO2 free

26

mg/L

SO2 total

89

mg/L

Ethanol

12.6

%

She has access to high pressure, 95% pure SO2 liquid that has a density of 1.46 g/ml. How many mL of the SO2 do you advise her to add? Show all work, units and assumptions

Volume

3,648

L

pH

3.24

SO2 free

26

mg/L

SO2 total

89

mg/L

Ethanol

12.6

%

Explanation / Answer

Given-

Density of 95% pure SO2 = 1.46 g/ml.

To protect the wine from microbial assault she should maintain a MSO2 of at least 0.80 mg/L

Step1-Calculate the g of pure SO2 in 1 ml of SO2 -

The SO2 is 95% pure and has a density of 1.46 g/mL

So in one mL there is 0.95 x 1.46 g/ mL = 1.387 g/mL of 100% SO2

To protect the wine from microbial assault she should maintain a MSO2 of at least 0.80 mg/L

Step 2- Convert   0.80 mg/L into g /ml

0.80 mg/L x 1g/1000mg = 0.0008 g/L

Step3- Calculate pure SO2 in 0.0008 g/L SO2

Pure SO2 = 0.0008 g / 1.387 g /ml = 0.000577 ml.

For 1 L of wine, 0.000577 ml of SO2 needed

So, for 3,648 L wine 3,648 x 0.000577ml = 2.105 ml of SO2 needed

We should advise her to add 2.1 ml of SO2 to make 3,648 L wine.

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