Metal finishing Q&As since 1989

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Cyanide anlaysis

2002

I am doing experiment with Iron addition to 30ppm CN solution. And then I want to measure the free cyanide that is left in the solution, (not complexed with the Iron).

Can anyone tell me if I can use the Hach Method 8027 to do this? That's the Pyridine-Pyrazalone Method. I am only interested in the free cyanide concentration and not the ferro- or ferric- cyanide concentration. Does the Hach method measures free cyanide or cyanide total?

Thank you!

Susanna Li
- Warren, Michigan, USA

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2002

You really should be seeking help from Hach. This method analyzes free cyanide in the range 0.001 to 0.240 mg/L CN¯ (may require sample dilution on your part) so it appears suitable for your purpose; it is more difficult to analyze total CN:

"The Pyridine-Pyrazalone method used for measuring cyanide gives an intense blue color with free cyanide. A sample distillation is required to determine cyanide from transition and heavy metal cyanide complexes." --- Hach Method 8027.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.