[znaes97]

Hello all,
I have a titration to determine the sodium carbonate content in a zinc plating solution. After performing the titration, the specified color changes were not seen. The procedure is as follows:

1. Pipette a 5ml sample of operating solution into a 250ml Erlenmeyer flask.
2. Add 100ml DI water
3. Add 0.5g indigo carmine indicator
4. Titrate with 0.94N sulfuric acid to a yellow-green endpoint.
5. Rezero the burette.
6. Add 5 drops of methyl orange indicator.
7. Titrate with 0.94N sulfuric acid to a gray-purple endpoint.
8. Add ~0.5g of indigo carmine indicator.
9. Titrate with 0.94N sulfuric acid to a blue endpoint.

When performing the titration, I never saw the yellow-green color shift. The solution went from orange-brown to a blue. If anyone has any advice or recommendations, they would be greatly appreciated. Thank you in advance.

[Borek]

The procedure is definitely incorrect.

It asks you to add the same indicator twice.

It asks you to titrate to pH well below neutral (gray-purple for methyl orange means pH around 3), then it asks you to titrate with an acid to endpoint that is around pH 12 (color change of the indigo carmine).

Not going to work.