The Karl Fischer titration principle relies on a chemical reaction where water reacts with iodine and sulfur dioxide in a buffered solution. T

 The Karl Fischer titration principle relies on a chemical reaction where water reacts with iodine and sulfur dioxide in a buffered solution. The reaction leads to the formation of hydrogen iodide and sulfur trioxide. The endpoint of the titration is reached when all the water in the sample has reacted with the titrant, and excess iodine is detected. 

Karl Fischer Titration: easy principle, 2 types, advantages ...

Here's a more detailed explanation:

Reaction:

The core of the method involves the reaction of water with iodine and sulfur dioxide, often in the presence of a base and a solvent like methanol. 

Titrant:

The Karl Fischer reagent contains iodine, sulfur dioxide, a base (like pyridine or imidazole), and a solvent. 

Volumetric vs. Coulometric:

Karl Fischer titrations can be performed in two ways:

Volumetric: Iodine is added to the sample from a burette. 

Coulometric: Iodine is electrochemically generated within the titration cell. 

Endpoint Detection:

The endpoint, indicating that all the water has reacted, is typically detected by a voltametric or amperometric method, which measures the excess iodine. 

Calculation:

The amount of water in the sample is calculated based on the amount of titrant (volume or charge) required to reach the endpoint.