Chrominfo: Identification test for barium sulphate

Learn the identification tests for barium sulphate through a laboratory experiment or practical.

Aim:

To perform an identification test for barium sulphate.

Reference: Indian Pharmacopoeia (IP) 2010

Requirements:

Glasswares and miscellaneous:

Test tube, measuring cylinder, pipette, glass rod, volumetric flask, beaker, dropper, rubber stopper, test tube stand, test tube holder, litmus paper, balance, etc.

Chemicals:

Barium sulphate (BaSO4), barium chloride (BaCl2), sodium carbonate (Na2CO3), lead acetate (Pb (C2H3O2)2), sulphuric acid (H2SO4), and hydrochloric acid (HCl), etc.

Theory of identification test for barium sulfate:

This identification of BaSO4 is usually based on the reactions of ions and cations present in the sample, by which we can determine the quality of the drug. Barium sulfate/sulphate is an inorganic compound. It is a crystalline white solid that is odorless. In water, organic solvents, and dilute acid and alkali solutions, it is insoluble.

Procedure:

For five minutes, boil 0.2 g BaSO4 in a 50% Na2CO3 solution. The salt is not soluble. By fusing it with anhydrous sodium carbonate or anhydrous potassium carbonate, it is converted into a less soluble salt. Filter the resulting mass after treating it with hot water. Perform barium tests on the residue collected on filter paper and for sulphate in filtrate collected after filtration.

BaSO3 + Na2CO3 → Na2SO4 + BaCO3

Identification tests for barium ion:

Dissolve a portion of the residue in HCl and perform a flame test. The presence of barium ions is indicated by the yellowish-green color of the flame.
Wash off the remaining residue with a small amount of water continuously. Wash off the other part of the residue with a small amount of water continuously. Add 5 mL of dilute hydrochloric acid to the residue and filter. To the filtrate, add 0.3 ml of dil. HCl. A white barium sulfate precipitate is formed, which is insoluble in nitric acid (HNO3).

Identification tests for sulphate ion:

To a portion of the filtrate, add 01 ml of barium chloride solution. A white precipitate formed from the formation of barium sulfate.
To 01 ml of filtrate, add 01 ml of lead acetate solution. A white precipitate formed from the formation of barium sulfate lead sulphate. Ammonium acetate solution and sodium hydroxide dissolve the precipitate.