ASTM E203 Test Method for Water Using Volumetric Karl Fischer Titration Scope:

ASTM E203 test provides a general guide to determine free water and water of hydration in most liquid or solid organic and inorganic compounds using volumetric Karl Fischer (KF) titration. This test uses automatic titration for determining the KF titration end-point potentiometrically.  This test method is applicable for both pyridine and pyridine-free KF reagents to determine water using volumetric titration. ASTM E203 is useful for the estimation of water over a wide concentration range i.e., parts per million (ppm) to pure water. 

Test Procedure:

For ASTM E203, the sample, containing 100 mg of water, is dissolved in an appropriate liquid. Then, it is titrated with a KF reagent that consists of sulfur dioxide, organic base, iodine, and a solvent that may be methanol, ethylene glycol, or 2-methoxy ethanol. The end-point of the titration is done amperometrically using a platinum electrode. A sharp change is noticed in the cell resistance when the iodine is reduced by sulfur dioxide in the presence of water.

Sample size:

The samples should be used as specified by ASTM E203. 

Data:

Water equivalent, E, of the KF reagent, in milligrams per milliliter

The water content of the sample, weight %

Conclusion:

ASTM E203 test provides a general guide to determine free water and water of hydration in most solid or liquid organic and inorganic compounds using volumetric Karl Fischer (KF) titration.