September 30, 2023

Caffeine: Identification and test for purity: Pharmaceutical Chemistry Practical

Caffeine: Identification and test for purity: Pharmaceutical Chemistry Practical

Limit test Chlorides, Sulphate, Iron, Heavy metals * Identification tests for Anions and Cations * Prep. & std Sodium Hydroxide, Potassium Permanganate * Assay Ferrous sulphate, Calcium gluconate, Sodium chloride, Ascorbic acid, Ibuprofen * Determination of Melting point & Boiling point * Preparation Benzoic acid from Benzamide, Picric acid from Phenol * Identification & purity test Aspirin, Caffeine


To perform and report identification test on the given sample of Caffeine as per Indian Pharmacopoeia (I.P.)



Thiel’s tube, Test tubes, Capillary.


Hydrochloric acid, potassium chlorate, tannic acid, iodine solution.


Caffeine is 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione or its monohydrate. Caffeine is a natural stimulant most commonly found in tea, coffee, and cacao plants. It works by stimulating the brain and central nervous system, helping you stay alert and prevent the onset of tiredness.

Procedure for Description:

Observe the given drug critically for the following description. Silky white crystals, white glistening needles or a white crystalline powder; odourless; sublimes readily.

Procedure for Solubility:

Perform solubility test in the different solvents. The drug is Freely soluble in chlorofom and in boiling water; sparingly soluble in water and in ethanol (95 per cent); slightly soluble in ether.

Procedure for Identification Tests:

A. To 10 mg in a porcelain dish, add 1 ml of hydrochloric acid and 0.1 g of potassium chlorate and evaporate to dryness on a water-bath. Expose the residue to the vapours of dilute ammonia solution; a purple colour is produced which disappears on addition of a solution of a fixed alkali.

B. To a saturated solution add a few drops of tannic acid solution; a white precipitate is produced which is soluble in excess of the reagent.

C. To 5 ml of saturated solution add 1.5 ml of 0.05 M iodine, the solution remains clear. Add a few drops of dilute hydrochloric acid; a brown precipitate is formed which dissolves on neutralization with sodium hydroxide solution.

D. Determination of Melting Point: The drug melts at about 238°C

•Observation Table:

Report on Identification Tests on sample of caffeine

Results: The given sample is found to be of ________________

With melting point ______________________

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