Qualitative Analysis Of Nitrogen, Halogen And Sulphur

Question 1

Lassaigne’s Test

Answer 1

A general test for the detection of nitrogen, sulfur, and halogens.
The organic compound is fused with metallic sodium to convert these elements into their respective sodium salts.

Question 2

Test for Nitrogen

Answer 2

Sodium fusion extract is treated with iron(II) sulfate and then acidified with sulfuric acid.
The formation of a Prussian blue color indicates the presence of nitrogen

Question 3

Test for Halogens

Answer 3

The sodium fusion extract is acidified with nitric acid and silver nitrate is added.
A white precipitate indicates chlorine, a pale yellow precipitate indicates bromine, and a yellow precipitate indicates iodine.

Question 4

Test for Sulfur

Answer 4

Sodium nitroprusside is added to the sodium fusion extract.
A violet color indicates the presence of sulfur.

Question 5

Beilstein Test:

Answer 5

A copper wire is heated and then exposed to the organic compound.
A green flame indicates the presence of halogens.

Question 6

Silver Nitrate Test

Answer 6

Used to confirm the presence of halogens.
A white to light yellow precipitate confirms the presence of halogens.

Question 7

Lead Acetate Test

Answer 7

Used to detect sulfur.
A black precipitate of lead sulfide indicates the presence of sulfur.

Question 8

Detection of Cysteine

Answer 8

The protein albumin contains the amino acid cysteine, which has a sulfhydryl group.
This can be detected by its reaction with lead acetate.