GFS Chemicals manufacturers the WatermarkÂ® brand of Karl Fischer Reagents. These high quality Karl Fischer Reagents are made fresh in the U.S. and are available to ship the same day or next day. The line includes reagents for volumetric and coulometric applications. Materials are available in pyridine and pyridine free solutions. GFS WatermarkÂ® Karl Fischer Reagents are designed for use with most titrators on the market. Coulometric Reagents have an extremely high water capacity. This capacity is in excess of 1000 mg of water/100 ml charge. To our knowledge, this is the highest water capacity available.