[chickapow]

Hi all,

I'm following http://www.titrations.info/EDTA-titration-zinc this method for a zinc titration I'm doing in the analysis of brass.

The starting solution is brass metal dissolved in nitric acid then diluted with water. Some potassium iodate is then added which precipitates the Cu²⁺ ions which are filtered off.

This leaves a solution with just zinc, which would mean I could titrate using the linked method.

However, for the zinc solution is a deep brown because of the iodine, making the indicator useless.

Is there any alternative method for removing the Cu²⁺ ions?

I'm open to any suggestion, however I must use a titrative method using the EBT indicator as that has been bought (at great expense specifically for this method).

Thanks in advance : )

[kriggy]

Could you get the amount of Cu in your sample and then do the titration by EDTA without removing Cu ions and then substract the amount of Cu you know is in solution?

[Borek]

Some potassium iodate is then added

Iodate or iodide?

1. Why don't you reduce the iodine to iodide?

2. Why don't you precipitate CuSCN? (Requires NaHSO₃ and NH₄SCN, this is a basis of a gravimetric Cu determination).

[chickapow]

Could you get the amount of Cu in your sample and then do the titration by EDTA without removing Cu ions and then substract the amount of Cu you know is in solution?

The added complication is that it is a zinc titration as part of my investigation. I have already carried out a Cu quantitative analysis, and now I need to do a Zn titration.

[chickapow]

Some potassium iodate is then added

Iodate or iodide?

1. Why don't you reduce the iodine to iodide?

2. Why don't you precipitate CuSCN? (Requires NaHSO₃ and NH₄SCN, this is a basis of a gravimetric Cu determination).

Does the CuSCN method produce a final colourless solution? Additionally, can KSCN be used to provide the SCN?

[Borek]

Does the CuSCN method produce a final colourless solution? Additionally, can KSCN be used to provide the SCN?

Nothing colored here so I guess yes, and no idea about KSCN - the recipe I have here call for NH₄SCN, whether it is because it was cheaper or there are some side reactions involving potassium I don't know.