[Mellitic]

I'm preforming a reaction with cyanoacrylates and I want to determine if cyanide is being liberated in the reaction (both for safety reasons and to check for side-reactions). 

I've found a couple of tests for cyanide, but I'm worried that the reagents and conditions will give me false positives/negatives.  Benzoquinone, Pyridine-barbituric acid, and copper+benzidine could all conceivably react with the cyanoacrylate SM or my product.  The prussian blue method requires strongly acidic conditions, which again might be an issue.  The precipitation of silver cyanide seems like a good test, but forming a white precipitate isn't a very distinctive readout.

The best I have so far is to add sodium thiosulfate to turn the cyanide into thiocyanate ions, then add a ferric salt to get red ferric thiocyanate.  I just can't find any procedure for this method, so I have no idea what pH, stoichiometry, or temp is needed.

[Arkcon]

A quick Google search for "cyanide spot test thiosulfate" brings up one Google books result: monsterous link{click}  which unfortunately isn't exactly what you're looking for..  It does however give a procedure, that may work in your case.  So at least you can narrow the search to practical methods with the term "spot test", eventually those lead to Feigl's spots tests, which are pretty comprehensive, and quick and easy to use.

[Mellitic]

Thanks for the suggestion Arkcon!  I wasn't familiar with Feigl's work.  Maybe this will help.  I've already search through many early 1900's texts hoping for one of those useful yet out-of-fashion qualitative tests.  I'm impressed by how many methods are out there, but also a little horrified at how many suggest tasting or smelling for the presence of HCN!  I found another possible candidate: a spot test of guaiac resin and copper sulfate from here.

More suggestions are certainly welcome.  If something works for me, I'll be sure to update here with my results.