ASTM D6304 Karl Fischer Water Determination

ASTM D6304 is the coulometric Karl Fischer method for water in petroleum products, lubricating oils, and additives. Laboratories use it when they need a specific water number — usually in mg/kg — rather than a generic “moisture” loss on heating.

The method allows more than one way to get the water into the titration cell. Direct introduction works for many hydrocarbons. Other procedures heat the sample and sweep the released moisture into the cell with dry inert gas, which is the evaporator path used on oils that would foul a direct injection. Sulfur species such as mercaptans and sulfides can interfere, so a D6304 result is not automatically valid for every chemistry.

This page is original prose and is not a reproduction of the standard. Buy the official text from the ASTM store.

ASTM Standard at a Glance

Related Products

Recommended equipment for ASTM D6304:

Choosing the right equipment for ASTM D6304

Coulometric Karl Fischer work is sensitive to cell condition, reagent quality, and how the water actually reaches the titrator. Oils that coat the electrode need the evaporator path, not a hopeful direct injection.

The Vero Scientific oil moisture analyzer (VeroDry) is the instrument linked to this method.