[eprigge]

I'm working on a old silver plating bath recipe that uses potassium ferrocyanide instead of cyanide BUT I think it may actually decompose into potassium and/or silver  cyanide in solution.  The bath is made up of potassium ferrocyanide, potassium carbonate and silver chloride.  There is a reaction and precipitate formed once the components are mixed, I think iron hydroxide or carbonate.

Naturally, the safety considerations are very different if you've got silver complexed by cyanide instead of ferrocyanide which is pretty harmless.  SO... how can I test for the presence of either silver cyanide or potassium silver cyanide (or free cyanide).  Of course I don't want the test to indicate the ferrocyanide complex.

Thanks!
Eric

[Alpha-Omega]

You can use ion chromatography with UV detection to determine the presence of metal cyanides.

Please see the attached Dionex Application Update 147 and Dionex Application Note 161.  Thie information at this link may be of interest to you: 

http://www1.dionex.com/en-us/lp44306.html

Additionally, if you go to the Dionex website:  www.dionex.com and type in your species of interest in the search field you will obtain a number fo hits.

The AS7/AG7 Column set will give you cyanide. Pdf attached.

You will also find a wealth of information on the EPA

http://www.epa.gov/


and ASTM (journals and publications) websites:


http://www.astm.org/cgi-bin/SoftCart.exe/index.shtml?E+mystore

http://www.astmpubs.com/

http://www.techstreet.com/info/astm.tmpl

[hmx9123]

Depending on the concentrations in question, you may be able to use generic qualitative analysis wet chemistry techniques to detect for the presence of cyanide vs. ferrocyanide. 

Of course, the other option is simply to drink it and see if you die.   If you do, then there was cyanide present. (This paragraph is a joke, just in case there was any doubt; never drink your chemistry).

[eprigge]

Thanks for the ideas.  Can you outline the generic qualitative tests one would use?  Ion chromatography would be great but I don't have access to a machine.

[Alpha-Omega]

Try this Link: 

http://en.wikipedia.org/wiki/Chemical_test_for_cyanide

I am also attaching a word document with a spot test for silver cyanide through conversion into silver chromate.

WATER ENVIRONMENT FEDERATION (WEF)

4500-CN-  CYANIDE  Standard Methods for the Examination of Water and Wastewater. 19th Edition. 1995. Andrew D. Eaton, Lenore S. Clesceri, Arnold E. Greenberg,  Eds. pages 4-18-4-35. (approved by Standard Methods Committee, 1990)

4500-CN-   A.   Introduction

4500-CN-   B.   Preliminary Treatment of Samples

4500-CN-  C.  Total Cyanide After Distillation

4500-CN-  D.  Titrimetric Method

4500-CN-  E.  Colorimetric Method

4500-CN-  F.  Cyanide-Selective Electrode Method

4500-CN-  G.  Cyanides Amenable to Chlorination after Distillation

4500-CN-   H.  Cyanides Amenable to Chlorination without Distillation (Short-Cut Method)

4500-CN-  I.  Weak Acid Dissociable Cyanide

4500-CN-  J.  Cyanogen Chloride

4500-CN-  K.  Spot Test for Sample Screening

4500-CN-  L.  Cyanates

4500-CN-  M.  Thiocyanate