ISO 6656:1984

Specifies the reference method. Below 50 mg of polymers per kilogram the presicion of the method is insufficient. The method consists in dissolving of a test portion in chloroform, after acid treatment, then filtrating through a sintered filter crucible, washing the crucible and its content, drying and weighing, followed by extraction of the polymers from the insoluble matter by boiling tetrachloroethylene, drying the crucible with its content and weighing again.