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### Topic: How to do a ppm calculation for sulphur dioxide in wine  (Read 24776 times)

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#### lab123

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##### How to do a ppm calculation for sulphur dioxide in wine
« on: March 12, 2004, 03:56:31 AM »
I've recently read an article called 'sulphur dioxide and tanin' by G.W.A Fowles. it talks about a titration between iodine and wine to determine the sulphur dioxide content. It gives this equation to work out the sulphur dioxide content in parts per million(ppm):

sulphur dioxide in ppm = 12.8* volume of iodine added(in cm3).

Does anyone know where does the value 12.8 come from?
« Last Edit: March 12, 2004, 06:55:53 AM by Mitch »

#### Mitch

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##### Re:ppm
« Reply #1 on: March 12, 2004, 04:06:22 AM »
This is the general formula for parts per million, but....

ppm = mass of the solute/ mass of the solution *10^6 parts per million

...If your density is approximately 1.0g/ml  you can just use this nifty trick
1ppm = 1mg/liter

« Last Edit: March 12, 2004, 04:07:17 AM by Mitch »
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#### lab123

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##### Re:How to do a ppm calculation for sulphur dioxide in wine
« Reply #2 on: March 12, 2004, 11:03:34 AM »
Hi! Can you show me how 12.8 is derived?

#### Bystander

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##### Re:How to do a ppm calculation for sulphur dioxide in wine
« Reply #3 on: March 13, 2004, 03:48:45 PM »
"12.8" is a meaningless number without information on the volume being titrated, the reaction, and the strength of the titrant (I doubt very much that the analysis is being done with elemental iodine).

#### hmx9123

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##### Re:How to do a ppm calculation for sulphur dioxide in wine
« Reply #4 on: April 15, 2004, 04:02:31 PM »
I used to TA a lab that actually calculted several things based on titration, including alcohol concentration and SO2 concentration.  There were no 12.8 figures in there.  I'm sure that number came from the concentration & volume of the iodine solution used.  If you're interested, I can post the part of that lab that dealt with the sulfur dioxide concentration.

#### AWK

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##### Re:How to do a ppm calculation for sulphur dioxide in wine
« Reply #5 on: April 16, 2004, 02:08:22 AM »
Concentration of iodine and volume of wine are always needed - then this number can be explained (probably concentration of I2=0.1 M)
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