The halogens, nitrogen, and sulfur are covalently bonded to the organic compounds are converted to various sodium salts formed during the fusion. Typically proposed reactions are:
:Na + C + N → NaCN
:Na + C + N + S → NaSCN
:2Na + S → NaS
:Na + X → NaX
The fate of the hydrocarbon portion of the sample is disregarded.
The aqueous extract is called sodium fusion extract or Lassaigne's extract.