Water determination in basic chemicals – solids, liquids and gases

Solids – salts, hydroxides, carbonates

Salts contain adherent or enclosed moisture. Adherent water can be easily determined as long as it is ensured that the salt does not dissolve. The working medium is a 1:3 (v/v) methanol–chloroform mixture. For the determination of the total water content, there are two methods available: the first using a solvent mixture in which the salt completely dissolves, e.g., in a 2:1 methanol–formamide mixture, and the second using the heating (oven) method, in which a dry gas stream transfers the water released to the titration cell.

During the Karl Fischer titration of inorganic hydroxides and carbonates, the weak acids methyl sulfuric acid and hydrogen iodide form in the titration cell and react with the alkaline hydroxides and carbonates, thus forming additional water. Therefore, the water content in hydroxides and carbonates has to be determined via the heating (oven) method.

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Liquids – inorganic acids, solvents, organic liquids

Sample bottles containing samples

Before water determination, inorganic acids such as HCl, HNO3, H2SO4, and H3PO4 must first be neutralized. HBr and HF are first absorbed in pyridine or in a solution of imidazole in dioxane before titration. HF attacks glass, which is why Karl Fischer titration is performed in plastic vessels with visual or photometric endpoint detection.

To learn more about the water determination in organic solvents and liquids, check out the dedicated web page and download the Karl Fischer monograph below.

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Gases – butane, propane, chloromethane, carbon dioxide, and hydrogen gas

Besides being used as a fuel in residential heating appliances, liquefied petroleum gas (LPG) is widely used as starting material in the chemical industry for the production of precursor products and derivatives. LPG is extracted from crude oil and natural gas and is the basis for the production of numerous organic compounds. Similarly, ammonia, hydrogen, and carbon dioxide are important gases in organic synthesis.

The presence of water in these gases is undesirable, as it can hamper the synthesis reaction and promote corrosion of the plant’s metal piping. Making sure that the LPG's water content is within the specifications can therefore help to keep maintenance costs low and improve the quality of the product.

Metrohm offers a dedicated system for the analysis of water in LPG, natural gas, and inorganic gases: the 875 KF Gas Analyzer. The system applies coulometric Karl Fischer titration, allowing you to obtain quick and accurate results within less than 5 minutes.

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Water in butane and propane

Butane and propane are the starting materials for the production of a vast variety of products. For instance, butane is used to synthesize 1,3-butadiene, which, in turn, is used as a monomer in the manufacture of synthetic rubbers. Another important use of butadiene is in the production of ABS, a plastic that finds many applications in the automotive and electronics industries.

Download the applications below to see how you can determine the water content in butane and propane using the 875 KF Gas Analyzer.

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Water in chloromethane

Chloromethane is a major compound in the production of silicone polymers and is used in the etherification of alcohols and phenols. The 875 KF Gas Analyzer is capable of analyzing the water content in chloromethane.

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Water in carbon dioxide and hydrogen gas

Hydrogen is used in the manufacture of important chemical compounds: ammonia and methanol. Additionally, it is an essential gas in refinery processes.

Carbon dioxide, too, is an indispensable compound in the chemical industry and is mainly used to produce urea and, in smaller quantities, methanol.

The applications below show how you can determine the water content in these gases using an 875 KF Gas Analyzer.

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