Qualitative analysis of unknown organic compound/s by lassaign tests (Sulphur).

 EXPERINMENT 04

Object

Qualitative analysis of unknown organic compound/s by lassaign tests (Sulphur).

Reference

1. Agarwal O.P., Practical Organic chemistry, published by Krishna educational publisher, Edition 2014, page no.26
2. Dr. Peesapati V., A comprehensive approach to practical orgaanic chemistry, published by PharmaMed Press, 2023, pg No 35

Requirement

Ignition tube, capillary tube, pipette, test tube, china dish, filter paper, funnel, unknown organic compound. (sod. nitro prusside, lead acetate)

Theory

The Lassaigne’s test, also known as the sodium fusion test, is a qualitative analysis technique used to detect the presence of nitrogen, sulfur, and halogens in an organic compound.

it utilizes the reactivity of sodium with the elements nitrogen, sulfur, and halogens in organic compounds. When heated with sodium, these elements form water-soluble salts, which are then extracted and tested using specific chemical reactions.

Procedure

Lassaigne’s  Extract)

1. Take a small piece of dry sodium metal in a fusion tube and heat it gently till the metal melts or fuses.
2. Add equal quantity of compound to this fused metal [ If he compound is a liquid then add two drops of it with a capillary]
3. Heat it gently then strongly till it becomes red hot.
4. Plung the red hot tube in 10 ml or ¾ of a test tube of distilled water taken in a porcelain dish,covering it immediately with an asbestos sheet crush the fusion tube completely.
5. Carry out more fusion in the similar way. Boil the extract for five minutes reduce the volume to about 5 ml and filter. Perform following test using this filtrate.

there are two methods for performing the test 

Test with sodium nitro prusside

1. Acidify the filtrate with few drops of dil acetic acid.
2. Add few drops of freshly prepared sodium nitro prusside 
3. Observe the color (Purple color shows the presence of sulphur)

Test with Lead acetate 

1. 1. Add few drops of lead acetate in solution.
   2. observe color (black color shows the presence of sulphur)

Observation

With Lead Acetate, If Black color is present —– Sulphur is present

With Sodium Nitro Prusside, If purple violet color is present —– Sulphur is present

Result:

Qualitative analysis of unknown organic compound/s by lassaign tests (Sulphur) was done successfully.