Nomenclature and General Principles: Detection of Other Elements (For CBSE, ICSE, IAS, NET, NRA 2022)

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Detection of Other Elements

Test for Sulphur

  • The sodium fusion extract or L. E: is treated with sodium nitroprusside.
  • The appearance of violet colour indicates the presence of S.

Violet Colour

Test for Halogen

  • L. E. is acidified with and then treated with .
  • A white precipitate soluble in indicates the presence of .
  • A pale-yellow precipitate partially soluble in indicates the presence of .
  • A yellow precipitate insoluble in shows the presence of .

white ppt. soluble in

Pale-yellow ppt. Partially soluble in

Dark-yellow ppt Insoluble in

Test for Phosphorous

  • The organic compound is heated with an oxidizing agent (sodium peroxide) .
  • Phosphorus is oxidized to phosphate.
  • The solution is then boiled with cone. and treated with ammonium molybdate.
  • A yellow precipitate confirms the presence of phosphorous.

Quantitative Analysis

Estimation of C and H

Liebig՚s Combustion Method

  • A known mass of compound is heated with .
  • The carbon present is oxidized to and hydrogen to .
  • The is absorbed in solution, while vapours are absorbed in anhydrous and weighted. (Fig)
Liebig՚s Combustion Method

Percentage of

Percentage of

Estimation of Halogen

Carious Method

A known mass of compound is heated with cone. in the presence of contained in a hard glass tube known as Carious tube (fig) in a furnace.

Carious Method
  • C and H are oxidized to and .
  • The halogen forms the corresponding . It is filtered, dried, and weighed.

Percentage of

Percentage of

Percentage of

Percentage of

Estimation of Sulphur

  • A known mass of compound is heated with fuming or sodium peroxide in the presence of solution in carious tube.
  • Sulphur is oxidized to and precipitated as .
  • It is filtered, dried, and weighed.

Percentage of

Estimation of Phosphorus

A known mass of compound is heated with fuming in Carious tube which converts phosphorus to (phosphoric acid) .

It is precipitated as ammonium phosphomolybdate by adding NH3 and ammonium molybdate .

It is filtered, dried, and weighted.

Percentage of

Developed by: