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Bromothymol Blue
Posted: 06 Jun 2008, 14:19
by joness
HELP!! I am having trouble making a solution of Bromothymol Blue. When i make it, it only goes blue for about a minute, then begins to turn green. I add the sodium hydroxide, drop by drop, but still goes green. Can anyone help?
Susie
Re: Bromothymol Blue
Posted: 06 Jun 2008, 14:35
by dime
Maybe try stronger NaOH - 1M?
Re: Bromothymol Blue
Posted: 06 Jun 2008, 14:39
by RosalieM
did you dissolve it in ethanol before making it up with distilled water? Maybe your water is a bit acidic? I agree with dime - maybe try stronger NaOH?
Re: Bromothymol Blue
Posted: 06 Jun 2008, 16:24
by Robb
Hi All,
The Bromothymol Blue needs to be GREEN. If you keep adding the NaOH you will eventually reach the pH that will cause the colour change. This is why your green colour is being changed to blue then back again.
Bromothymol Blue is called that, because the GREEN solution changes to a prominent BLUE colour in the required pH region.
When you make this solution up just make sure that it is a prominent GREEN colour.
This will put you on the right track. --Good try though in problem solving the solution problem--
Cheers,
Robb.....