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Chemical Analysis - Tin in Zinc

2004

Hi,

I am looking for a method of analysing a sample of Zinc with approx. 28% Tin content. It is the Tin content I am interested in. I dissolve in HCL, cool and titrate using Iodine, with starch as an indicator. The Iodide "goes off" quickly and I would like to know if there is a better method.

Thank you.

John Marshall
Wire manufacture and plating - Sheffield, South Yorkshire, England

John,

I am assuming you are trying to analyse a Zinc/Tin alloy as you stated that you dissolve it in HCl first. The problem you are facing with your method is that tin is not stripped with HCl and hence you are getting little if any tin into solution and seeing an immediate endpoint.

Dissolving the sample with nitric acid might help, although the nitric acid will interfere in the titration and must be removed first, perhaps you could try a nitric/sulfuric 30/70 mixture and then boil the sample to heavy white fumes, although I would suggest also doing a blank with no metal to ensure you have removed all the nitric. Better still, if you have access to a nitrous oxide AAS, you should be able to strip in nitric and analyse directly.

Peter Van de Luecht
- Melbourne, Victoria, Australia
2004