Standard Test Method for Water Using Volumetric Karl Fischer TitrationTranslate name
STANDARD published on 1.4.2016
Designation standards: ASTM E203-16
Publication date standards: 1.4.2016
The number of pages: 9
Approximate weight : 27 g (0.06 lbs)
Country: American technical standard
Category: Technical standards ASTM
free water, Karl Fischer reagent, pyridine-free, volumetric, water, water of hydration,, ICS Number Code 71.040.40 (Chemical analysis)
|Significance and Use|
4.1 Titration techniques using KF reagent are one of the most widely used for the determination of water.
4.2 Although the volumetric KF titration can determine low levels of water, it is generally accepted that coulometric KF titrations (see Test Method ) are more accurate for routine determination of very low levels of water. As a general rule, if samples routinely contain water concentrations of 500 mg/kg or less, the coulometric technique should be considered.
4.3 Applications can be subdivided into two sections: (4.4 Water can be determined directly in the presence of the following types of compounds:
Note 1: Some acids, such as formic, acetic, and adipic acid, are slowly esterified. For high accuracy with pyridine-based reagents, use 30 to 50 % pyridine in methanol as the solvent. When using pyridine-free reagents, commercially available buffer solutions can be added to the sample prior to titration. With formic acid, it may be necessary to use methanol-free solvents and titrants Note 2: Examples of stable aldehydes are formaldehyde, sugars, chloral, etc. Formaldehyde polymers contain water as methylol groups. This combined water is not titrated. Addition of an excess of NaOCHNote 3: Weak amines are considered to be those with Note 4: Examples of stable ketones are diisopropyl ketone, camphor, benzophenone, benzil, dibenzolacetone, etc.
Note 5: Sulfuric acid up to a concentration of 92 % may be titrated directly; for higher concentrations see .
Note 6: Compounds subject to oxidation-reduction reactions in an iodine-iodide system interfere.
1.1 This test method is intended as a general guide for the application of the volumetric Karl Fischer (KF) titration for determining free water and water of hydration in most solid or liquid organic and inorganic compounds. This test method is designed for use with automatic titration systems capable of determining the KF titration end point potentiometrically; however, a manual titration method for determining the end point visually is included as . Samples that are gaseous at room temperature are not covered (see ). This test method covers the use of both pyridine and pyridine-free KF reagents for determining water by the volumetric titration. Determination of water using KF coulometric titration is not discussed. By proper choice of the sample size, KF reagent concentration and apparatus, this test method is suitable for measurement of water over a wide concentration range, that is, parts per million to pure water.
1.2 The values stated in SI units are to be regarded as standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific warnings are given in and .
1.4 Review the current Safety Data Sheets (SDS) for detailed information concerning toxicity, first aid procedures, and safety precautions for chemicals used in this test procedure.
|2. Referenced Documents|
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