-->

Organic Chemistry – Some Basic Principles And Techniques

Question
CBSEENCH11007622

How will you detect the presence of sulphur in an organic compound by oxidation test?

Solution

Oxidation test (for volatile compounds): The organic compound is fused with a mixture of potassium nitrate and sodium carbonate. Sulphur present gets oxidised to sodium sulphate. 
3 KNO subscript 3 space space rightwards arrow space space space 3 KNO subscript 2 space plus space 3 straight O
Na subscript 2 CO subscript 3 space plus space straight S space plus space 3 space left square bracket straight O right square bracket space rightwards arrow space space space Na subscript 2 SO subscript 4 space plus space CO subscript 2

The fused mass is extracted with water and filtered. The filtrate is acidified with hydrochloric acid and then a solution of barium chloride is added. Formation of white precipitate indicates the presence of sulphur in the organic compound. 
Na subscript 2 SO subscript 4 space plus space BaCl subscript 2 space space rightwards arrow space space space stack BaSO subscript 4 with White space ppt. space below downwards arrow space space plus space 2 NaCl