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topic 18723

Nickel titration or atomic absorption


I am Tom Holt from a computer circuit board manufacturer. Our E'LESS Nickel process uses an EDTA-murexide titration for g/Liter Nickel.

If a sample is diluted and tested by Atomic Absorption the results are many times lower. If digested with acid the results are nearly twice the titration method.Is the titration reported as Free (available) nickel in the complexed E'LESS bath? If so an A.A. method is not possible.

Thank you,

Tom Holt
- SL City, Utah


I would expect atomic adsorption to be more accurate than titration because AA works on the energy released by electrons changing energy levels when they are heated in the flame. Titration depends on the reactibility of the species being detected and if it is complexed, it may not behave itself properly. Titrations are also dependent on the ease at which the end point can be seen, so there is a built-in dilution effect here. The simple remedy is to make up a standardised known nickel solution and see which one gives the most accurate answer.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

First of two simultaneous responses--Dec ++

I can't really explain your AA problem. I would just advise that you stick with the titration method. All EN baths are set-up to be controlled by that method. It is certainly accurate and precise enough for that purpose. If your lab is setup for it, it is also faster than an AA determination. An AA method does not really have any advantage to offer in this particular case. Titration theory- The measurement by the titration method is total nickel, not free nickel. The addition of ammonia serves as a demasking agent so that the nickel is free to complex with the murexide indicator. When EDTA is added, the EDTA-nickel complex is favored over the murexide-nickel complex. Once all of the murexide has been "freed" by the EDTA, you see the color change from the free murexide ions.

Jon Barrows
Jon Barrows, MSF, EHSSC
Springfield, Missouri

Second of two simultaneous responses-- 2002

An electroless nickel bath is in a constant state of change, even when it is hot between loads. Using AA to control the bath is like measuring with a micrometer and cutting with a sledge hammer. Done properly, the EDTA analysis is more than accurate enough to control an EN tank. Ultra accuracy is unnecessary and has changed by the time the analysis is completed.

James Watts
- Navarre, Florida


Hi, James,

Do you have ideas that what others metal-indicator is suitable to substitute the Murexide? I'm asking this because as I know from my suppliers, Murexide is banned by Malaysia because of contain Narcotic. So, beside Murexide, what others indicators can be used? Any change of the procedure if substitute the indicator from Murexide to it?

Thank you very much!


Happy New Year to all !

Wymen Lee
- Penang, Malaysia


Wymen, Unfortunately, I sold most of my plating books. If memory serves me correctly, Erichrome Black T is a direct substitute for Murexide.The end point is a bit tricky, so play with it before you try to do it for real. It is an indicator that is from Kodak and you probably will have to find a supply house that carries Kodak material or will get it for you. Your EN supplier should be able to get you this as a substitute procedure.

James Watts
- Navarre, Florida

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