Filter circles - quantitative. Slow ashless filter paper. Equivalent to blue ribbon. Retention of very fine particles. Standard paper for critical gravimetric analysis of fine precipitates like barium sulfate or metastannic acid. - Filtration speed acc. to DIN 53237: 140 s. - Thickness: 0.17 mm. - Weight: 85 g / m². - Ash-content: < 0.01 %. Filter circles - quantitative. Slow ashless filter paper. Equivalent to blue ribbon. Retention of very fine particles. Standard paper for critical gravimetric analysis of fine precipitates like barium sulfate or metastannic acid. - Filtration speed acc. to DIN 53237: 140 s. - Thickness: 0.17 mm. - Weight: 85 g / m². - Ash-content: < 0.01 %.