Qualitative tests for Uric acid in given sample [CCF-SEMV-DSCC-11-P]

 [ Test Solution: 0.2% Uric acid solution in 1% Na₂CO₃ or dilute NaOH ]

[How to get Uric acid?

Horbaczewski Synthesis (Urea + Glycine)

This is one of the simplest methods, where uric acid is formed by heating urea with the amino acid glycine.

The Reaction:

H₂N-CH₂-COOH + 3(NH₂)₂CO   ➡️ 🔺 ➡️  C₅H₄N₄O₃ + 3NH₃+2H₂O

Procedure:

1. Mix dry Urea and Glycine in a 3:1 molar ratio.

2. Heat the mixture in a flask to approximately 180 degree C- 200 degree C.

3. The mixture will melt and then solidify as ammonia gas is evolved.

4. The resulting solid is then dissolved in a dilute alkali (like KOH) and precipitated back out using a dilute acid (like HCl) to obtain purified uric acid crystals.]

Experiment	Observation	Inference
Litmus Test:A piece of red litmus paper is dipped into the test solution.	Red paper turns blue.	Uric acid may be present.
Reduction test:             Schiffs Test: Few drops of test solution  upon a filter paper moistenes with silver nitrate solution.	Black coloration occurs.	Presence of Uric acid is confirmed.
Black colouration is due to reduction of AgNo3 to colloidal silver.
Folin’s Test: 2 drops of Folin’s phosphotungstic acid reagent to about 3 ml of the test solution.	Blue color is obtained.	Presence of Uric acid is confirmed.
[Chemical reaction: In alkaline solution, uric acid is oxidized to allantoin & it reduces alkaline phosphotungstic acid to tungsten blue. Thus the blue coloration is due to reduction of  phosphotungstate  by uric acid in alkaline solution.]
Murexide Test:[Confirmatory Test] 5 ml of sample solution is heated to concentrate it to about 1 ml. Transfer the solution into a porcelain dish. Add 3 drops of concentrated HNO3 & evaporate carefully over a low flame. Instead of solution, a small quantity of solid  sample is taken   ·         A drop of dilute ammonia  is added to the small amount of residue.   ·         A drop of NaOH solution  is added to the small amount of residue.	Yellow red residue left.    Residue turns purple.     Residue turns blue violet.	Uric acid is present in the sample.
[Chemical reason: Purple colour is ammonium purpurate & blue violet is sodium purpurate. Concentrated Nitric acid oxidizes uric acid to dialuric acid & alloxan. They condense to form alloxantin, which under the action of ammonia ,is converted first to purpuric acid & subsequently to its ammonium salt. Uric acid ➡️ concentrated nitric acid➡ Dialuric acid + alloxan  ➡ condensation ➡Alloxantin. Alloxantin ➡ ammonia ➡  Purpuric acid➡  Ammonium purpurate.]

Qualitative Test for  Urea :https://biomassfootprints.blogspot.com/2025/12/qualitative-tests-for-urea-in-given.html

Qualitative Test for Ammonia: https://biomassfootprints.blogspot.com/2025/12/qualitaive-test-for-ammonia.html