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Name: Ron
Status: other
Grade: other
Location: WI
Country: USA
Date: N/A 

This is more a procedure question! I am preparing samples for some soil tests. The procedure is to mix a soil sample with an extraction solution which is 3% acetic acid and 10% sodium acetate then filter out the solids.

The procedure calls for the use of a filter funnel and gravity. Is there any significant downside to using a B├╝chner funnel (same filter paper)with an aspirator or even using a centrifuge to reduce process time?

A vacuum filter with a Buchner funnel is probably the preferred method, with the possible exception of the centrifuge if you have one available. Your intuition that minimizing time is on target.

Vince Calder


I do not know of any data that says your analysis will be any different if you use a Buchner funnel with an aspirator as opposed to a gravity filtration. There are, of course, certain techniques (wetting the Buchner filter, applying vacuum before filtering, disconnecting the aspirator before turning it off, etc) that make Buchner filtration more effective, and there are issues that are of concern with Buchner filtration (doing a rinse before the cake cracks, clogging of the filter paper, etc.), but keeping all these in mind, I think the technique should work equally well and be faster to boot.

Greg (Roberto Gregorius)
Canisius College

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