Qualitative Filter Papers-Grade 5: 2.5μm

Whatman gridded filters have clearly defined grid lines spaced at 3.1 or 5 mm intervals.

The special ink used is nontoxic and completely
free from bacterial growth inhibitors.

Whatman black mixed cellulose esters are available plain for automatic colony
counting applications, as well as gridded to assist in manual counting procedures.

Black membranes provide contrast between residue or cell colors and the filter
without having to counter-stain the membrane.

Slightly more retentive than Grade 1 with a corresponding increase in filtration time (i.e., slightly slower filtration speed).

More absorbent than Grade 1. In addition to general filtration in the 8 μm particle size range, the extra absorbency is utilized, for example, to hold soil nutrient in plant growth trials.

Also used for monitoring specific contaminants in the atmosphere and in soil testing.