To determine the mass of potassium carbonate and potassium bicarbonate in a solution separately, what indicator should be used in the titration method?
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I want to titrate potassium carbonate and potassium bicarbonate in a solution using hydrochloric acid. What kind of indicator should I use, and what are the steps for the procedure? This post was last edited by keaidexujie on 2009-3-13 20:54.]
Check the determination of the mixed alkali; it should be roughly the same. Use phenolphthalein as an indicator first, and then methyl orange.
I think it is mixed-base analysis; methyl orange should be used first, followed by phenolphthalein. !
It was reflected incorrectly; the one above is correct.
1. Determination of mixed bases http://www.it68.net/new_view.asp?id=6884 2. Determination of mixed bases (dual-indicator method) http://www.17baba.com/infor/show_document_detail.asp?id=14678
A pH meter can also be used; the first one is adjusted to 8.3 and the second one to 4.0. That’s what we did, and it seems to be a bit more accurate than using indicators. The color change when methyl orange goes from yellow to red isn’t very noticeable, so it’s better to use a pH meter!
The original poster is correct; the pH of a 0.1 mol/L solution of sodium bicarbonate (or potassium bicarbonate) is around 8.3, while the pH of a saturated carbonic acid solution is around 3.9. Therefore, it is better to use a pH meter as an endpoint indicator.
Measure the phenolphthalein alkalinity, and then measure the methyl orange alkalinity.