oz82 Posted March 1, 2007 Share Posted March 1, 2007 Lets say you collected a sample and you knew it had Aluminium Sulphate and Sulphuric Acid in it. You try to determine the amount of Sulphuric Acid and get a surprisingly high result. The results could be overstated because the barium perchlorate titration you used is specific to sulfate and cannot differentiate between H2SO4 or aluminium sulfate. Does anybody know of an analysis that would show the difference?? Ta Link to comment Share on other sites More sharing options...
woelen Posted March 1, 2007 Share Posted March 1, 2007 Measure the pH, e.g. by titrating with a solution of NaOH of known concentration. Especially if the concentration of acid is high, this gives a good and accurate result. Use an indicator, which changes color, when pH goes from 4 to 5 or somewhere around that. Using such an indicator, you take into account the somewhat acidic properties of Al(3+)-ions. Link to comment Share on other sites More sharing options...
John Cuthber Posted March 1, 2007 Share Posted March 1, 2007 You could measure the aluminium and work out how much sulphate the aluminium sulphate contributed. A titration using a pH meter as the "indicator" would, I think, give breakpoints corresponding to the titre of H2SO4, HSO4 and Al+++ so that would give quite a lot of information. Link to comment Share on other sites More sharing options...
Crooked Mick Posted May 11, 2007 Share Posted May 11, 2007 One of the standard methods is to titrate with borax, sodium tetraborate decahydrate. This is a "secondary" standard and a sufficiently accurate solution for most purposes can be made by dissolving a weighed amount in water after GENTLE drying. However I do not know whether the presence of a lot of Al2(SO4)3 would affect the end point a great deal. Indicator was, if memory serves methyl red in presence of methylene blue. Colour change was purple -green, more or less. See standard methods for determination of sulphur in coal by the high temperature tube furnace method. Can't be more specific, it's 18 years since I've done this. Link to comment Share on other sites More sharing options...
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