Summary for ammonia concentration in brass bath Discussion
Ammonia concentration in a brass plating bath is discussed as a measurement problem with limited direct guidance. Jason Deible asked whether there is a way to test ammonia in the bath. Dave Wichern suggested that an ion-selective electrode (ISE) might work, but did not provide a detailed procedure. SK Cheah described running a 400-liter brass bath for barrel plating chain components and said he adds ammonia daily in fixed amounts rather than titrating for ammonia content; he reports no trouble maintaining the copper/zinc deposition ratio. Matina Tsolaki then asked about using a Kjeldahl-style analysis for ammonium in the bath, including whether the sample should be digested first with FeSO4 and then distilled with NaOH, or whether all reagents should be combined at the start. The thread does not show a definitive analytical method, but it suggests ISE as a possible test and also shows one practitioner relying on controlled additions instead of routine ammonia analysis.
Q. Is there any way of testing the ammonia
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Jason Deible
– Grand Rapids, Michigan
2003
A. Maybe ISE would work.
James Totter, CEF
– Tallahassee, Florida
2003
Analysis for ammonium in brass plating baths
Q. Hello, Could you please advise on analysis of ammonium in brass plating bath? I only found one application bulletin which says with Kjeldahl method. Is there another way to find out the concentration of ammonium in my solution so as to keep stable the ratio of Cu:Zn 70:30 in my deposit?
Thank you so much for your help
Matina
MATINA Tsolaki
– THESSALONIKI GREECE
November 2, 2015
A. Mr. Trotter is right on, as usual.
Do ISE via an ammonia selective electrode. It will be necessary to use the method of additions, if you want to avoid the distillation. The math is kind of complicated but it’s doable.
Or just go ahead and do the darn distillation. It is not so hard and you can then get to your answer via simple acid base titration.
Dave Wichern
Consultant – The Bronx, New York
November 6, 2015
A. Hi Matina.
I run a 400 liter brass plating bath using barrel to plate chain components. I use brass salts from chemical suppliers. ammonia is added daily about 100 ml per operation day. On longer shutdown…200 ml. I do not titrate for ammonia content. I have no problems keeping the Cu/zinc deposition ratio. Hope this helps
SK Cheah
– Penang Malaysia
December 1, 2015
Q. Hello, is there anyone that has done Kjeldahl analysis to determine ammonium in brass plating bath? I have found an analysis that says 5 ml sample with 4 mo FeSO4 and 15 ml NaOH 20% to the distillation flask and begin distillation immediately. The ammonia is distilled in a solution of H3BO3 2% and then titration with HCl 0.1M.
One question is: do we put all reagents together from the beginning? Shouldn’t we first do the digestion with sample and FeSO4? And then distillation with NaOH?
If someone knows an analysis please advise.
Thank you,
MATINA TSOLAKI [returning]
– THESSALONIKI GREECE
November 26, 2015