Whatman 1442-125 Ashless Quantitative Filter Paper, 12.5cm Diameter, 2.5 Micron, Grade 42 (Pack of 100) Diameter: 12.5cm Retention: 2.5m A world standard for critical gravimetric analysis A Whatman cellulose filter is manufactured from high quality cotton linters treated to achieve a minimum alpha cellulose content of 98% Typical analytical precipitates include barium sulphate, metastannic acid and finely precipitated calcium carbonate