Total acid content of grape juice to be made into wine (expressed as grams of tartaric acid equivalent per 100ml). My uncle makes his own wine and has to rely on a wine school to do the testing of the grape juice for him, which is sometimes an inconvienance. The idea is that the acid content of grapes varies (varying mixes of mostly tartaric, some malic, and some citric acid, which makes an endpoint a pain in the ass to find) and there is an ideal acidity for each type of wine. After seeing that the wine shcool gives acid adjustments in 100ml of Tartaric acid portions (yes, I said ml...the lack of accuracy scares me), I was very much compelled to do the testing myself. So, NaOH solution at 0.05M and titrated 10ml samples a few times, screwing up the endpoint because the grape juice messes with the phenolphthalein. If you dilute the sample and use a hefty number of phenolphthalein drops, there is an definite endpoint although it is not too sharp (for these purposes, a few drops either way doesn't really mean much). So I have Molarity of the hydronium ion concentration and I need something they call total acid content. It took me a few hours to decipher that this meant "Pretend all the hydronium ions come from tartaric acid and convert to grams/100ml" I got 0.55 which is quite low for making any wine and justified the addition of tartaric acid (although I doubt that the prescribed addition was anything close to what it should have been). I've done several other, but this was the most interesting (and citizen chemistry)
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Topic: What titrations have you tried? (Read 132773 times)