These Pyrex® fritted disc funnels are very useful in preparative work, or in making separations where it is necessary to wash the precipitate and redissolve with chemicals which would attack filter paper. The angle of the funnel body facilitates the removal of precipitates. These funnels are available in three different porosities of fritted ware so that precipitates varying in size can be filtered at maximum speed with no sacrifice of retention. Porosity is controlled in manufacture, and discs are individually tested and graded into these classifications: coarse porosity (40 to 60µm), medium porosity (10 to 15µm) and fine porosity (4 to 5.5µm). The porosity for the pore diameter of the filter is determined in the same manner as specified in ASTM E-128 "Maximum Pore Diameter and Permeability of Rigid Porous Filters for Laboratory Use."