Object:
To test the urine for urea, proteins, ketones and Sugar.
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Requirements:
Test-tubes, soybeans flour, litmus solution, acetic acid, phenolphthalein, sodium hydrate, copper sulphate, sulpho- salicylic acid, ammonium sulphate, ammonia, sodium nitroprusside, Benedict’s reagent and samples of urine.
Procedure:
The following procedure is adopted for the test of urea, protein, ketone and sugar from the samples of urine.
1. Urea test:
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Normal urine contains 2 to 3 per cent urea. Take 2 cc of urine in a test-tube, add a pinch of soyabean flour, a little litmus solution, and a few drops of 1% acetic acid.
In a few minutes the mixture becomes alkaline and turns blue because of decomposition of urea into ammonium carbonate.
Alternatively, take 5 cc of urine in a test tube, add 2 or 3 drops of phenolphthalein, and 0-1 gm soyabean flour.
Mix the contents and place test tube in a water bath at 50°C. The contents will turn pink showing urea.
2. Protein test:
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A. Normal urine is free from proteins, but at times it may contain albumin, globulin, and other proteins.
Heat urine to almost dryness by evaporation. Then heat this in a dry test- tube, fumes of ammonia are given off.
Remove from flame and cool, add a few drops of sodium hydrate and a drop of copper sulphate solution. A pink colour appears showing the presence of proteins.
A. Filter urine to remove any turbidity and to make it clear. Take this clear urine in a test tube and boil only the upper part for two minutes holding the test tube by the bottom end.
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If the upper part becomes turbid and cloudy, then it may be due to albumin or phosphates. To find out add 3 to 5 drops of 5% acetic acid, if turbidity appears or persists, then it is due to the presence of albumin in urines.
B. Take some urine in a test tube and boil the upper part only, add several drops of strong nitric acid slowly.
If a flocculent precipitate appears and perists in the upper part of the tube, then it shows the presence of albumin.
D. Filter urine to remove any turbidity. Take 5 ml of filtered urine in a test tube, add 6 drops of 20 per cent sulphosalicylic acid, if a cloud is formed it shows the presence of protein.
3. Ketone test:
In metabolism fats and some amino acids are broken down into ketone bodies. The ketone bodies comprise acetone, aceto acetic acid, and beta hydroxybutyric acid.
In a test- tube take 20 ml of urine and saturate it with ammonium sulphate crystals. Add 2 or 3 drops of ammonia and a few crystals of sodium nitroprusside, shake the tube well.
If ketone bodies are present a reddish-purple colour appears in a few minutes; if, however, a brown colour appears, it shows the absence of ketones.
4. Sugar test:
A. Normally there is no sugar (glucose) in urine. If there is any albumin in urine, then it is removed by adding a few drops of 5% acetic acid, then boil and filter to make the urine clear and protein free.
Take 8 drops of this urine, add 5 ml of Benedict’s reagent, boil the mixture and allow to cool.
If the solution is a clear greenish-blue then it shows absence of glucose. Boil a bluish-green colour with some yellow precipitate shows 0 2% glucose.
A deep yellow to orange precipitate shows 0-5% glucose. A heavy orange brown to red precipitate shows 1 to 3% glucose.
B. Make urine clear and protein-free as before. Take some of this urine in a test-tube. In another test-tube take an equal volume of Fehling’s solution.
But the two test-tubes separately and when boiling mix them together; a yellow to brick-red precipitate shows presence of glucose.