Metal finishing Q&As since 1989

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Need to determine carbonates in cadmium plating solution using autotitration

I am an Environmental Chemist and work for an aviation company who carrys out electroplating as one of their accessory services. We have recently decided to start doing all the analysis of our solutions in-house using an auto-titrator. This equipment works very well for many of the tests which need to be carried out but I have a problem with determining sodium carbonates in a cadmium solution. Does anyone else have success with auto-titration for determining cadmium carbonates?

Samantha Mackins
- Kent, United Kingdom
2005

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There are a number of ways that it could be done. Most of them will be indirect methods and you will need to verify the accuracy of your method. One indirect method is to use a barium ISE and titrate with barium chloride. Barium carbonate will precipitate as long as there is carbonate in the sample. When the carbonate has all reacted, the ISE will start detecting the barium ions from the titrant. The success that you will have with this will depend a good deal on your software, instrumentation, and your knowledge about the proper use of ISE's. If your titrator allows for thermometric detection, a simple direct method is possible with barium chloride.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

2005

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Do you have an analysis for troubleshooting carbonates in a Cadmium plating tank?

Diane Brady
Plating /Analysis Tech - Baltimore, Maryland, USA
September 17, 2008

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September 19, 2008

Diane,
pipette [pipettes on eBay or Amazon] a 10ml sample into a 600ml squat form beaker [beakers on eBay or Amazon], add 300 mls of de-ionised water and heat on a hot-plate with a boiling rod XX DO NOT BOIL XX.
Add 10% Barium Chloride solution until no more precipitate forms then filter through a Whatman 40 filter paper. Wash the filter paper and beaker thoroughly with hot de-ionised water until the final washing no longer turns pH indicator paper blue. Transfer the filter paper back to the original beaker, pulp up the filter paper and add 200 mls of de-ionised water and a few drops of methyl orange [on eBay or Amazon] indicator.
Titrate with 1.0N Hydrochloric Acid while stirring the pulped paper with the boiling rod.
End-point is Orange TO red
Calculation is Titre mls 1.0N Hydrochloric Acid x 5.3 = g/l Sodium Carbonate

Good luck and hope this helps!

Nigel Gill, BSc MIMF MRSC
- Glasgow, Scotland