G'day. Thank you for your kind (if somewhat misplaced) faith in me.
I read the content of that URL above, and it does sound extremely
complicated and academic for the average jeweller. I offer the
following suggestion, and that's all it really is;
I would have thought that converting the cyanide to the ferric salt
by simply adding plenty of strong ferric chloride solution, letting
it clear a little by standing and then adding a few more drops of
ferric chloride solution until no more precipitate forms. This
should produce ferric cyanide which is quite insoluble, and should
be harmless. Dry it off in a tray of sawdust in the sun, parcel it
in old newspaper and send to the tip. This only goes for small
quantities - less than 100 grams cyanide. For large amounts of
waste cyanide, seek advice from professional disposal companies.
Be assured, there will be far worse things in that rubbish tip than
a few grams of ferric cyanide. Now call me a vandal and 'ungreen'.
Cheers for now,
JohnB of Mapua, Nelson NZ