Flash link:  https://vlab.amrita.edu/repo/CHE/ORG/Detection-of-elements-LassaignesTest/Detectionofelements.swf

 

Procedure:

 

• Preparation of Lassaigne’s Extract:

 

A small pellet of metallic sodium together with a little of the substance is heated to red hot in an ignition tube. It is then suddenly plunged into about 10ml of distilled water in a china dish. The mixture is boiled well and filtered. The filtrate is used for doing the following tests.

 

1. Detection of Nitrogen:

 

To a little of the filtrate add equal volume of freshly prepared FeSO₄ solution that is boiled and cooled. Then add few drops of FeCl₃ solution and acidify with dil HCl.  Blue colour precipitate indicates the presence of nitrogen.

 

 

2. Detection of Chlorine:

 

To a little of the filtrate add few drops of dil HNO₃ that is boiled and cooled.  Then add AgNO₃ solution to it. A white precipitate soluble in ammonium hydroxide confirms the presence of chlorine.

 

 

3. Detection of Sulphur:

 

To a little of the filtrate add few drops of freshly prepared sodium nitroprusside solution. Appearance of brilliant violet colour indicates the presence of sulphur.