Urinalysis - The Carter Center

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A. Ferric Chloride Test
Principle: FeCl 3 oxidizes the melanogen to melanin.
Procedure
• To 5 ml of freshly voided urine, add 1 ml 10% FeCl 3 drop by drop to
precipitate all the phosphates.
• Add drop by drop 10% HCl to dissolve all the precipitate and it forms
different color.
• Centrifuge and examine for black or gray precipitate of melanin.
If melanin is present, decant the supernatant fluid and add Na 2 CO 3 until
alkaline to litmus, melanin precipitates will dissolve again, and then add
10% HCl until acid to litmus; melanin precipitates again as gray or black
sediment when centrifuged.
Preparation of 10 % Hydrochloric Acid Solution (See Reagent Number
10).
B. Thormahlel Test
Principle
Sodium Nitroprusside is reduced to ferocyanide (prussian blue) by
reducing action of melanogen.