In the Lassaigne's test for the detection of sulfur,which substance is responsible for the formation of black precipitates?

Name the methods used for determining the molecular mass of organic compounds.

In $Lassaigne's$ test,the organic compound is fused with $Na$ metal followed by extraction with distilled water. Which of the following is not a possible product of this fusion reaction?

Which one of the following reactions does $NOT$ belong to "Lassaigne's test"?

In which of the following compounds will nitrogen not be detected by the Lassaigne test?

Three students,Manish,Ramesh,and Rajni were determining the extra elements present in an organic compound given by their teacher. They prepared the Lassaigne's extract $(L.E.)$ independently by the fusion of the compound with sodium metal. Then they added solid $FeSO_4$ and dilute sulphuric acid to a part of the Lassaigne's extract. Manish and Rajni obtained prussian blue colour,but Ramesh got red colour.
Ramesh repeated the test with the same Lassaigne's extract,but again got red colour only. They were surprised and went to their teacher and told him about their observation. Teacher asked them to think over the reason for this. Can you help them by giving the reason for this observation? Also,write the chemical equations to explain the formation of compounds of different colours.