I have to do soap titration but I have a problem with my IPA. It's acidic when I add bromophenol blue it turns to yellow. How can I adjust pH to 7.0?? I tried to adjust pH by using phenophthalein in IPA as an indicator and add 0.1M NaOH in IPA. It turn to pink color but when I stir it just disappear and pH still be acidic.Then How much NaOH do I need to neutralize IPA??
I have another questions about soap titration. My experiment is use adsorbent instead of using water wash so I need to determine amount of soap. When I vary the percentage of adsorbent, soap should be decrease right?? So do I have to weigh biodiesel with the same weight for every portion?? or the more adsorbent I use, the more biodiesel's weight I have to weigh??
Thanks for answering my question....

Tuckky,
After adding your Bromo and IPA (if it turns yellow), add your .1M NaOH until the bromo turns back to blue (while stirring). This is called a blank. It's not bringing your IPA back to PH7.
Then proceede with your titration using your .__ M acid of choice.

Same weight for every portion. If I'm interpreting correctly.

Thanks so much Double D.
I've read the experiment that suggest to use neutralized isopropanol as a solvent but my IPA isn't neutral. Do I need to neutralize it before using?? Because when I added unwashed bidiesel in IPA and added 1%phenophthalein/IPA, the solution didn't turn to pink although it has a lot of base in there. I'm curious it's because of my IPA is acidic.

Tuckky,
A blank should be performed before the titration to negate the acidity of the IPA.