Volhard-Harvey test: Estimation of chloride in urine

Chloride concentration of urine is dependent upon the amount of chloride present in the ingested food.

 Volhard-Harvey Method:

PRINCIPLE:

The chloride in the urine is precipitated as silver chloride with a measured excess of silver nitrate The excess of silver nitrate is treated With ammonium. presence of Ferric Ammonium Sulphate as an indicator.

  • 1 Concentrated HNO3,
  • 2 AgNO3 solution,
  • 3 Ammonium Thiocyanate,
  • 4 Ferric Ammonium Sulphate ( Ferric alum ).
  • 5 8% KMnO4 solution.Volhard-Harvey test

Procedure:

  • To 5ml urine in a 100ml Erlenmeyer flask add lml Conc. HN03 and few drops of Ferric Ammonium sulphate, an indicator.
  • If a red colour. is produced at this stage, add 800 KMnO4 solution drop by drOp with shaking until the colour disappears.
  • Now add slowly 10ml Silver Nitrate solution, with continuous shaking. A White precipitate of silver chloride will be formed.
  • Titrate the excess of silver nitrate left in the flask, with ammonium thiocyanate in the burette. The appearance of first permanent tinge of red brown indicates the end point.
  • Note the burette reading and calculate the amount of chloride in the urine sample.

CALCULATIONS:

  • Average volume of urine = 15OOml/day
  • Volume of urine used = 5ml
  • Volume of AgN03 used = 10ml
  • Volume of NH4CNS used =  ‘a’ ml Volume of AgNO3 used to precipitate the chloride in the urine = 10 -‘a = ‘b’ ml
  • Amount of chloride precipitated by lml AgN03 = 10mg
  • ‘b’ m1 AgNO3 Will precipitate = ‘b’ X 10 = ‘y’mg
  • Therefore, 5m1 urine contains = ‘y’ mg Cl _ as NaCl
  • 1ml urine will contain = ‘ y ’ mg Cl as NaCl/ 5
  • 1500 ml urine will contain = ‘ y’ X 1500 / 5
  • = ‘ C’ mg Cl as NaCl/day.

NORMAL RANGE:

Urinary Chloride = 7-10gm C1 as NaCl/ day.

Increased intake in diet. Drinking large volumes of water.

Decreased intake in diet. Due to excessive loss in vomiting, diarrhoea, and Profuse sweating.

During fasting. Nephritis associated with oedema.

 

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