Filter Papers, Litmus & pH Strips

A coarser grade filters faster but catches only larger particles, while a fine grade filters slower but traps finer solids.

Choose a filter paper pore size fine enough to catch the particles in your sample without clogging too quickly.

Litmus paper gives a quick red-or-blue acid-base answer, while a full pH strip gives a more precise reading across a wider range.

Choose chromatography-grade paper specifically when separating mixed pigments or compounds, since ordinary filter paper isn't designed for this.

Litmus paper only shows whether a solution is acidic or alkaline through a red or blue colour change, while pH paper gives a more precise reading across a numbered scale.

No, filter papers are designed for single use, since trapped particles clog the pores and affect the next filtration.

This usually means too much sample was applied to the starting spot, or the solvent level was too high and touched the sample directly.

A medium-grade general-purpose filter paper suits most classroom filtration, unless your experiment specifically calls for a finer or coarser grade.

Keep strips in their original container away from moisture and light, and they'll stay accurate for the manufacturer's stated shelf life, usually a year or more unopened.