Karl Fischer



The Water Determination Test (Karl Fischer Method) is designed to determine water content in substances, utilizing the quantitative reaction of water with iodine and sulfur dioxide in the presence of a lower alcohol such as methanol and an organic base such as pyridine, as shown in the following formula:

H2O + I2 + SO2 + CH3OH + 3 RN       [RNH]SO4CH3 + 2 [RNH]I

La reacción se desarrolla hasta que se ha consumido el agua en su totalidad


  In the volumetric titration method, iodine required for reaction with water is previously dissolved in water determination , and water content is determined by measuring the amount of iodine consumed as a result of reaction with water in a sample.

La valoración volumétrica Karl Fischer es apropiada para muestras que tengan un contenido en agua desde 100ppm al 100%.


Generally, the apparatus consists of an automatic burette, a backtitration flask, a stirrer, and an equipment for amperometric titration at constant voltage or potentiometric titration at constant current.

Because water determination  is extremely hygroscopic, the titration apparatus should be protected from atmospheric moisture. Silica gel or calcium chloride for water determination is usually used for moisture protection

Solución con un componente

El reactivo se compone de yodo, dióxido de azufre e imidazol. El solvente es metanol.

El reactivo con un componente se manipula fácilmente y tiene un precio económico. Sin embargo, no ofrece estabilidad en el título.

Solución con dos componentes

El reactivo es una solución de yodo con metanol. El solvente para la muestra contiene dióxido de azufre e imidazol disueltos en metanol.


In the coulometric titration method, first, iodine is produced by electrolysis of the reagent containing iodide ion, and then, the water content in a sample is determined by measuring the quantity of electricity which is required for the electrolysis (i.e., for the production of iodine), based on the quantitative reaction of the generated iodine with water.


Usually, the apparatus is comprised of an electrolytic cell for iodine production, a stirrer, a titration flask, and a potentiometric titration system at constant current. The iodine production device is composed of an anode and a cathode, separated by a diaphragm. The anode is immersed in the anolyte solution for water determination and the cathode is immersed in the catholyte solution for water determination. Both electrodes are usually made of platinum-mesh.

Bir cevap yazın

Başa dön tuşu