Sodium fusion test
The sodium fusion test is used in elemental analysis for the qualitative determination of the presence of halogens, nitrogen and sulphur in a sample. It was developed by J. L. Lassaigne.
The test involves heating the sample strongly with clean sodium metal, "fusing" it with the sample. A variety of techniques has been described. The "fused" sample is plunged into water, and the usual qualitative tests are performed on the resultant solution for the respective possible constituents.