Hi,

When doing determinations using a rankin, you add mixed indicator to
the Hydrogen peroxide in the pear shaped flask. You then titrate until
an end point is reached (ie the colour changes). You then perform the
rest of the procedure and re-titrate back to the same end point to
work out your SO2 levels.

My question is once you have completed your determination, if wish to
perform a second determination, do you need to change the indicator /
hydrogen peroxide / NaOH solution in the pear flask?

I wonder because you are starting from the same point (ie having
titrated until an end point is found)...

Any info would be appreciated

AB1