For researchers who made solutions a quarter-century ago, filtration involved deftly folding a round piece of filter paper into a triangular shape so that it would fit inside the inverted cone of a funnel. Once the paper was fitted inside the funnel, they could filter practically any solution, even those thick with solute--providing they had hours of time to spend watching the clear liquid drip into a flask as the particulate material in the funnel grew thicker and thicker.

If they were in a real hurry, they could add a vacuum pump to the filter and flask, to pull the particle-free solution through the filter faster. There were limitations to such filtration systems, though, such as trying to remove the rubber stopper holding the funnel from the flask, after the vacuum had pulled it tightly into the neck.

While filter paper and funnels will always have a place in chemistry...

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