2013: Advent Chemistry: Filtration

by on December 2, 2013
An open box of round filter papers

Filter paper

You all know what a filter is. It’s that thing you make coffee with. It’s a way of seperating solid particles from liquids. A sieve is a filter, if not a very fine one. A teabag is a filter with leaves inside.

It is one of the most basic bits of laboratory equipment. Half the things you make are crystals (white ones), floating around in liquids (clear, colourless). You’ve got to get the crystals out of there somehow, and by far the simplest way is to pour the whole lot through a filter.

Traditional filtration uses a circle of filter paper, folded into a cone, and sat in a conical glass funnel. You pour your mixture into the funnel and the particles are trapped, leaving the liquid to drip slowly out of the bottom.

Very, very slowly.

It’s a tedious process, but it works. You split off one part of the mixture from the other, so that you can do things to your useful crystals and discard your waste solution. Or you can do things to your useful solution and discard your waste crystals. It’s usually the former, but it is very important to be certain before you throw anything away. Trust me. Having to start over because you poured all your products down the drain is rubbish.

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