Lassaigne’s test is used to detect the halogens, nitrogen and sulphur present in an organic compound. Except for fluorine, all halogens are detected by Lassaigne’s test. In Lassaigne’s test, an organic compound is fused with metallic sodium to convert these elements into water–soluble sodium salt. Lassaigne’s test for halogens involves treating the sodium extract with silver nitrate. A precipitate of silver chloride, bromide and iodide indicates the presence of halogens. Silver fluoride is soluble in water and does not precipitate and, thus, this method cannot be used for the detection of fluorine. Lassaigne’s test was developed by a French Chemist, J.L. Lassaigne.