Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: lab123 on March 12, 2004, 03:56:31 AM
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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?
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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
Let me know if you need more info. :)
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Hi! Can you show me how 12.8 is derived?
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"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).
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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.
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Concentration of iodine and volume of wine are always needed - then this number can be explained (probably concentration of I2=0.1 M)