[SinkingTako]

For EDTA titration we are provided with xylenol orange and ET black indicator both in the solid form. (1% in KCl). For a standard titration of maybe 25ml of unknown how much indicator should we put? Anyone has a reference to the intensity of the colour of the solution that we should get? How much indicator will be "too much" that it affects the reading? Thanks!

[Borek]

For a standard titration of maybe 25ml of unknown

What unknown?

I have never used xylenol orange. ET black - just till the solution has a visible tint.

[Arkcon]

Sorry, the only answer I can give is "don't us too much."  Too much will affect the titration, you will have to read the protocol, or try it and see.  Sometimes the method calls for one "drop" as arbitrary as that is, or I'm required to add 0.5 ml of phenopthalein, as an example.  But I know if I add 20 drops, the endpoint won't be sharp and reproducible.

[SinkingTako]

What unknown?

I have never used xylenol orange. ET black - just till the solution has a visible tint.

Unknown is zinc or magnesium ions.

The problem is more of, "how much is too much". Actually I'm having a bit of trouble with EDTA titration: I can't seem to find the end point. Most of the time the solution is pink even after adding excess EDTA, then upon standing for 3 minutes or so the solution turns blue. Tried gently heating the solution but not much luck either. Maybe really just need more patience...

[Borek]

What is the procedure you follow? Have you adjusted pH before titration?