0.22 97 60 s 75% 14.3 9.5 cm 41 No. 5b Fast flow rate, high purity. Ashless. General gravimetric analysis, retention of SrSO 4, BaSO 4, HgCrO 4, and collodial dispersions. 5-10 µm 0.21 108 195 s 90% 19.4 7.0 cm 40 No. 5c Medium flow rate, high purity <5 µm