Karl Fischer titration modified

For efficiency of desiccants in drying acetone see Burfield and Smithers [7 Org Chem 43 3966 1978]. The water content of acetone can be determined by a modified Karl Fischer titration [Koupparis and Malmstadt A/w/ Chem 54 1914 1982]. 

Although the DL 40 was capable of performing Karl Fischer water titrations and Mettler developed a separate microprocessor-controlled push-button operated DL 18 KF titrator, they also introduced as an all-purpose apparatus the improved DL 40 RC (see Fig. 5.11) with a dual titration head and with a modified software program to handle the new two-component titrants for Karl Fischer titration (see pp. 204-205). The instrument can also be expanded into an automatic series titrator by connecting the RT 40 sample transport for 16 samples and storage of 50 sample weights from a connected balance this series routine can be interrupted at any time after completion of the titration in progress. 

In their Progress Report No 20-310 (Ref 20) are given descriptions and evaluations of the following methods of moisture detn a)Abder-halden Drying Procedure (by loss of wt) b)New Procedure for Determination of Moisture by Loss of Weight c)Oven-Drying at 130° d)Modified Karl Fischer Titration Apparatus for Use with AN Coated with ZnO e)Q-Metry Method (attempts to use this method were unsuccessful)... 

The condensable part of a sample is separated from carbon dioxide by an expansion through cold traps. The condensate in the cold traps is weighed and analyzed with Karl-Fischer titration (water) and HPLC (carbohydrates). The modifier mass is calculated by weight difference. 

In the coulometric version of the instrument, the iodine necessary for reaction is generated electrochemically by applying electrical pulses to the electrode. In this case, a modified Karl Fischer reagent is used which contains iodide instead of iodine. An iodide solution is in contact with the anode in one compartment of the electrolytic cell, which has a diaphragm between the anodic and cathodic regions (Fig. 19.11). Thus, the volume of reagent, which is the indicator in the classical titration method, is replaced by a more precise quantity of current, obtained coulometrieally. 

It would be desirable to have a standard method for determining VOC. However, there is little agreement as to what that standard method should be. Methods for determination of VOC are available in Reference 210. Methods for determining VOC of waterborne coatings is made difficult because of the need to determine water content. A modified Karl Fischer method in which the water in a coating is azeotropically distilled before titration is most accurate and convenient (217). 

In joint researches carried out by Eurisotop, this method was used in a somewhat modified form as a macro method weight of sample 85 g, temperature 700 C, the water formed is carried by the hydrogen stream, is absorbed in Karl Fischer solution and titrated (76). 

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