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Problems with silver cyanide bath


I am a lab supervisor at a barrel electroplating shop currently having problems with a cyanide silver plate bath. The bath is leaving a very dull, white finish on small parts of nearly every metal. The most difficult thing about this is that another silver bath with same potassium cyanide/potassium silver cyanide concentrations is working fine. Temperature in each bath is lower than normal (about 10 degrees F less) but this doesn't explain why only one will not plate. I suspect it may be high carbonate concentrations in the problem bath but I do not know how to test for this or what to do to correct it. Any help would be appreciated.

Dom Sideri
Laboratory supervisor - Lawrence, Massachusetts


Do you have Hull cell test equipment and have you tried it?

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


Dear Mr Sideri,

To analyse for Carbonate content: Pipette accurately a 10ml sample of plating solution into a 600ml squat form beaker. Add 300 mls of de-ionised water and heat on a hot-plate with a boiling rod in the beaker.*DO NOT BOIL** Add 10% Barium Chloride solution until no more precipitate forms in the beaker then filter through a Whatman number 40 filter paper. Wash the filter paper and beaker thoroughly with hot de-ionised water until the final washings no longer turn pH indicator paper blue. Transfer the filter paper back to the original beaker, pulp up and add 200ml of de-ionised water and a few drops of Methyl Orange indicator solution. Titrate with 1.0N Hydrochloric Acid while stirring the pulped filter paper with the boiling rod. End-point is; Orange to Red.


Titre mls x 5.3 = g/l Sodium Carbonate
Titre mls x 6.91 = g/l Potassium Carbonate

- Blantyre, Glasgow, Scotland

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