G’day. There are many ways of destroying cyanides or rendering them
to an innocuous condition. However, some of the most effective
methods (such as treatment with sulphur dioxide, etc) can be ruled out
for most jewellers whose use of cyanide is fairly minimal - compared
with professional platers and gold recovery plants. The simplest and
cheapest way of detoxifying cyanides in solution is to add ferrous
sulphate solution in excess; that is, to add a little more of a
fairly strong solution after no more precipitate is formed.
For instance, to detoxify a bombing solution, say, one would make up
a very strong solution of ferrous sulphate (Exact amounts are
unimportant) and add it to the cyanide preferably in a transparent
vessel with constant and turbulent stirring. The liquid will
immediately become more or less opaque with the precipitation of
ferrous cyanide, which is quite insoluble. Allow to settle, then add
a little more ferrous sulphate to determine that there is no further
precipitation, but to be certain, add a further few mls. Mix this
liquid with plenty of sawdust; that is, enough to make a heap which
seems fairly dry. Spread this mix onto plastic trays or polythene
sheets, weighted to avoid wind dispersal, and leave in the sun. When
quite dry, bundle and take to the usual waste disposal area, where it
can be scattered. It will not produce a poisonous leachate.
Incidentally ferrous sulphate solution is given to persons who have
taken cyanide internally, so as to act as an antidote to the poison -
only the administration of it has to be very quick indeed - VERY
quick!! – Cheers now,
John Burgess; @John_Burgess2 of Mapua Nelson NZ