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Karl Fischer

The Karl Fischer Titration Method You Should Know!

Created By: Hyprowira | Published Date: 21 December 2020 | Last Modified: 21 December 2020

In 1935, a scientist from Germany named Karl Fischer concluded a discovery that provided a new point of view in the scientific calculations of the time. He found that sulfur dioxide added to a reaction would determine the water content in the titration. This discovery became known today as the Karl Fischer titration method.


What is Karl Fischer Titration?

Karl Fischer titration is a scientific method used to determine the water content in various samples. This concept refers to the titrimetric method in the Bunsen reaction involving sulfur dioxide, iodine, and aqueous solutions.

In its calculation, Karl Fischer titration involves three main components, namely an analytical balance with a minimum resolution of 0.1 mg, a long syringe with a small needle, and a Karl Fischer reagent which is used to determine the water content.

All components in the instrument must always be placed in an area with a constant room temperature and humidity level. That way, external factors such as temperature and humidity will not affect the accuracy of the moisture calculation.


Principles of Karl Fischer Titration

The oxidation of sulfur dioxide by iodine is the main principle used in the Karl Fischer titration. In a buffer solution, the combination of the two types of solutions can determine the water consumption in the solution which helps calculate the water content as the final product. In other words, the Karl Fischer titration will reach the final stage when the iodine and the water titrating agent are in balance.

If there is excess iodine, the double-platinum electrode, which acts as an indicator, will change color. When this happens, the titration must be stopped immediately. The water content can then be determined by the amount of reagent that has been added to the solution.


Karl Fischer Titration Method

Basically, the Karl Fischer titration method is categorized into two methods, namely the volumetric and coulometric methods. However, as the application develops, the two methods can also be combined into a combined or hybrid method.

The following is a brief explanation of the three methods used in the Karl Fischer titration process.


1. Volumetric Method

Volumetry is a great way to calculate the lowest water content, for example in the range 0.005-0.01% (50-110 ppm). This method is carried out by adding Karl Fischer reagent consisting of a methanol solution with the addition of a mixture of sulfur dioxide, iodine, and pyridine. The solution is titrated into the sample using an electric burette. Determination of the water content can be done by involving the volume of the solution added.


2. Coulometric Method

The next method of Karl Fischer titration is coulometry. This calculation is carried out in an electrochemical process and involves only one iodine solution. The amount of iodine solution added will be calculated during the electrochemical process. The solution is reduced when it reacts with water, resulting in a colorless endpoint.


3. Hybrid Method

The third method called the hybrid method is a combination of the two previous methods, namely volumetry and coulometry. As the name suggests, this method combines the two working principles above. The iodine solution produced in the electrochemical process will be calculated until the water content exceeds a predetermined level. Once known, additional solutions will be added at the same time.


That is information about the meaning, principles, and Karl Fischer titration method that you need to understand. In order to make the procedure for determining the water content of the sample easier and more accurate, you need to choose the most appropriate device.

The Karl Fischer titrator from Toledo can be one of the main solutions. This superior device provides real functions for testing water content in turbine oil, hydraulic control oil, and various other samples.