In this volhard method of chloride determination post we have briefly explained about principle, requirements, reagent preparation, volhard titration method procedure, calculation.
What is Volhard Method?
A chloride blood test measures the amount of chloride in your blood. Chloride is a type of electrolyte. Electrolytes are minerals that are electrically charged that help control fluid quantity and the acid and body balance.
Often chloride is used to diagnose or monitor conditions such as renal disease, insecurity of the heart, liver disease and higher blood pressure, together with other electrolytes.
Volhard Method Principle
Volhard titration method uses the Volhard chloride estimation, protein being oxidized by the open Carius method using a solution of silver nitrate in concentrated nitric acid. The organic matter is destroyed and the chloride precipitated at the same the excess silver nitrate in then titrated with standard thiocyanate using ferric alum as the indicator.
1. Test tube
2. Test tube stand
3. Glass burette
4. Conical Flasks
5. White tiles
1. Silver Nitrate
2. Nitric Acid
3. Ammonium Thiocyanate
4. Ammonium Ferric Sulfate
1. 0.05 N Silver nitrate: Dissolve 0.895g of silver nitrate in about 2 ml of water and then make up to 100 ml with concentrated nitric acid. The solution keeps in a brown bottle for volhard titration method.
2. 0.02 N Thiyocyanate: 15.6 gm of Ammonium thiocyanate (NH4SCN) to a flask add 100 ml of water, and swirl to dissolve the NH4SCN. When solution is complete, filter through a hardened filter paper, or other suitable medium. Dilute the clear filtrate to 1 L with water and mix. Store the solution in a tightly stoppered glass bottle.
3. 5% Ferric alum: Dissolve 5gm of ammonium ferric sulfate in about 20 ml of water and then make up to 100 ml with double distilled water for volhard titration method.
Volhard Method Procedure
1. Pipette a sample in to clean dry conical flask and run it slowly with constant shaking, 3ml of silver nitrate solution.
2. Add 2 ml of concentrated nitric acid and heat over a Bunsen flame until digestion has occurred and the solution is pale Yellow in colour.
3. If the colour is deep yellow it can be discharged by adding a few drops of saturated potassium permanganate solution and warming again.
4. This should not be necessary with plasma. The digestion usually requires only one to two minutes.
5. When the digestion is completed, cool and add 6 ml of 5% ferric alum. Then titrated with 0.02N thiocyanate until a reddish brown colour persisting for ten to fifteen seconds is obtained.
6. To determine the standard add 2 ml of nitric acid and 6 ml of ferric alum solution to 3 ml of the silver nitrate solution, cool and titrate with 0.02N thiocyanate.
7. The difference between the two titration gives a measure of the amount of chloride in 1 ml serum and urine in terms of a 0.02 N solution in volhard titration method.
Volhard Method Calculation
Titration value of standard: ———– ml, B: Titre value of serum: ——————- ml
The amount of chloride in 100 ml of serum: (A –B) x 20 = ————- mg of chloride.
Titration value of standard: ———– ml, B: Titre value of urine: ——————- ml
The amount of chloride in 100 ml of urine: (A –B) x 20 = ————- mg of chloride.
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