What is Volhard method?
The volhard method is an indirect or back titration method in which an excess of a standard solution of silver nitrate is added to a chloride containing sample solution. The excess silver is then back titrated using a standardized solution of potassium or ammonium thiocyanate with ferric ion as an indicator.
What is modified Volhard method?
Modified volhard method :- 1. When chloride are analysed the volhard method has to slightly modified. 2. During Titration the solution is contact with two precipitation stimuantaneously silver chloride and ammonium thiocyanate which has different solubility.
Why is the Volhard method performed in an acidic system?
The titration must be carried out in an acidic solution to prevent the precipitation of Fe3+ as Fe(OH)3. The Volhard method was first published in 1874 by Jacob Volhard. The third type of end point uses a species that changes color when it adsorbs to the precipitate.
What is fajans method?
The precipitation titration in which silver ion is titrated with Halide or thiocyanate ions in presence of adsorption indicator is called as fajan’s method. This method is generally used for the quantitative analysis of halide ions or thiocyanate ions.
What is the main difference between Mohr method and Volhard method?
The key difference between Mohr Volhard and Fajans method is that Mohr method refers to the reaction between silver ion and halide ion in the presence of chromate indicator, but Volhard method refers to the reaction between excess silver ions and halide ions.
What is the role of nitrobenzene in assay of sodium chloride?
Explanation: The nitro benzene or dibutyl phthalate is added to coagulate the silver chloride precipitate so that it will not interfere with the titration of excess of silver nitrate by forming a layer over silver chloride and this avoids the need for filtration.
Which indicator is used in modified Volhard method?
The method of Volhard uses iron ions as indicators. An oxidizing agent such as AgNO3 (or any anionic solution) is used to titrate the acidic first analyte (halide ion solution). Titration is carried out with KSCN standard solution using iron ion (Fe+3) as an indicator.
Why nitrobenzene is used in Volhard method?
➡️ In the Volhard method chlorides are first precipitated with excess silver nitrate, then excess silver is titrated with potassium (or sodium) thiocyanate. Before titration we add some small volume of a heavy organic liquid that is not miscible with water (like nitrobenzene, chloroform or carbon tetrachloride).
What is the basis of complexometric titration?
Complexometric titration are those reactions where a simple ion is transformed into a complex ion and the equivalence point is determined by using metal indicators or electrometrically.
What is the difference between Volhard and Fajans method?
Mohr method is the reaction between silver ion and halide ion in the presence of chromate indicator, while Volhard method refers to the reaction between excess silver ions and halide ions. Fajans method, on the other hand, refers to the adsorption reaction between silver halide and fluorescein.
Why it is called Argentometric method?
It is a type of precipitation titration which involves the use of silver ion which is taken from its Latin name argentum. So, the word argentometric is also taken from Latin word argentum. The titrations with silver nitrate are known as argentometric titration.
What is Mohr’s method?
This method determines the chloride ion concentration of a solution by titration with silver nitrate. As the silver nitrate solution is slowly added, a precipitate of silver chloride forms. Ag+(aq) + Cl–(aq) → AgCl(s) The end point of the titration occurs when all the chloride ions are precipitated.