Determination of Water Content in Hexachlorobenzene Using Karl Fischer Titration

Product Group

Halogenated hydrocarbons

General Information concerning the product group

Halogenated hydrocarbons

Halogenated hydrocarbons can in most cases be titrated by the Karl Fischer method without any problems as is the case for hydrocarbons. No interferences are to be expected from the chemical structure. To overcome solubility problems of unpolar or weakly polar substances, the addition of a solubiliser to the solvent is necessary. In the case of long-chain and cyclic hydrocarbons, long-chain alcohols (e.g. decyl alcohol) or chloroform are thus recommended. Toluene, xylene or chloroform improve the solubility of aromatic compounds. Recommended methods are both the volumetric titration with one or two component reagents, as well as the coulometric analysis. The latter is predominantly applied for low water concentrations (< 0.1 %). If chlorinated hydrocarbons contain free chlorine it is necessary to reduce it prior to KF analysis. This is best achieved through attachment to unsaturated compounds, e.g. through conversion with tetradecene.

Special Information concerning the sample and the methods

This substance is hardly soluble in methanol. Titration should thus be carried out in the presence of toluene, xylene or chloroform as solubilisers, or rather with specific KF solvents for non-polar substances.

Titration one component system

Reagents:

Titrant
188002 Aquastar™ - CombiTitrant 2 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 2 mg water

Solvent
50 mL 188020 Aquastar™ - CombiSolvent oils - Solvent for volumetric Karl Fischer titration with one component reagents for oils

Titration Parameters:
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
2 g

Procedure:
The titration medium is first placed into the titration cell and titrated dry by means of the titrant. Then the sample is added from a weighing boat (exact sample weight determination by weighing of weighing boat before and after addition) and tthe itration is started.

Titration two component system

Reagents:

Titrant
188011 Aquastar™ - Titrant 2 - Titrant for volumetric titration with two component reagents, 1 mL = approx. 2 mg water

Solvent
30 mL 188015 Aquastar™ - Solvent - Solvent for volumetric titration with two component reagents
and
10 mL 108661 Xylene - null

Titration Parameters:
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
2 g

Procedure:
The titration medium is first placed into the titration cell and titrated dry by means of the titrant. Then the sample is added from a weighing boat (exact sample weight determination by weighing of weighing boat before and after addition) and the titration is started.

Materials

     
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