Principle of Reaction The Bunsen reaction between iodine and sulfur dioxide in an aqueous system is the basis for the Karl Fischer Reagents reactions. When you titrate the KF reagents in a titration cell, the following reactions take place: The first reaction is that between iodine and sulphur dioxide in the presence of a neutralizing base to form an alkyl sulphite intermediate. The common base used in Karl Fischer titration is pyridine, primary amines such as imidazole can also be used.
In the Volumetric Titration, you use a KF Solution containing dissolved iodine as the titrant until the presence of a trace excess iodine is detected at the endpoint. You determine the amount of water by measuring the iodine required to react with the water content in your sample as read from the burette volume of the Karl Fischer solution.
In the Coulometric procedure, you add your sample to an electrolytic solution consisting of iodide ions and other KF reagents. You then observe the production of iodine from the electrolytic oxidation of iodide ions as you titrate.
The iodine produced in this reaction is proportional to the quantity of electricity required for the oxidative conversion of iodide ions into iodine up to the end point presence of a trace of excess iodine. Limitations and Precautions: You should not use the KF reagents for samples containing redox-active constituents such as dimethyl sulfoxide because the constituents may react with the reagents and give incorrect results.
Coulometric reagents do not need assessment. Another advantage is that they can be used repeatedly. A dehydrating solvent suitable for the sample is placed in a flask. Titrant is used to remove all moisture from the solvent. The sample is then added. Solvent methonal ,. Sulphur dioxide,. Buffer Imidazole. The experiment of Karl Fischer titration can be performed in two different methods. They are listed below.
This particular technique is suitable in determining water content down to 1 percent of water. Here, the endpoint is detected potentiometrically. Here, the endpoint is electrochemically detected in this experiment. Iodine needed for the KF reaction is obtained by anodic oxidation of iodide from the solution. It can be used in technical products such as plastics, oils, gases,. It is used in cosmetic products,.
It is used in pharmaceutical products,. It is used in the industry. Prepare a solution by mixing mL of methanol and mL of pyridine. Now, add g of iodine to the solution and cool it. Then, take a mL graduated cylinder and add mL of pyridine to it.
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