Drop-wise addition of NaOH in the vicinity of the equivalence point is essential to
create a satisfactory plot. Make sure that you calculate ΔpH/ΔmL as you go. This
permits precise determination of the end points.
4. Once you have passed through the first end point ΔpH / ΔV will fall off in magnitude. Have the
supervisor check your results at this point, then proceed to ascertain the second endpoint using
the same approach in step 3. The volume of NaOH may again be increased in the initial stages
(~5 mL) until you approach the second end point. The volume of NaOH added between the 1st and
2nd endpoints (V2) will be about the same as that observed for the first equivalence point (V1).
5. When the second inflection point has been reached, turn the magnetic stirrer off, remove the
pH electrode from the solution, wipe carefully with a clean tissue and place in the original flask
of distilled water. Leaving pH electrodes in solutions of high pH can damage them.
6. The titrated solution can be discarded down the sink.
DO NOT THROW THE BUG OUT WITH THE SOLUTION!
Replace it on the magnetic stirrer.