STEM Education Poetry

Funnel Analysis

“To isolate via filtration,
Consider the process notation:
Whether vacuum or gravity 
Will the product compatibly 
Obtain, through work-up situation.”

The 10 April 2021 limerick discussed two additional work-up techniques useful in the organic chemistry laboratory: vacuum filtration and gravity filtration. Each is accomplished via the use of a specific type of set-up requiring a specific type of funnel, a fact which provides this essay’s title.    

“To isolate via filtration, /
Consider the process notation…”

This poem notes the distinction between two different techniques with confusingly similar names (both involving filtration).  To complete an organic chemistry work-up and isolate a target compound, one must first decide which type of filtration is most useful, or “[c]onsider the process notation.”    

“Whether vacuum or gravity /
Will the product compatibly /
Obtain, through work-up situation.”

Often in organic chemistry lab, a chemist seeks to separate a liquid from a solid via some kind of filtration, a relatively simple task accomplished by using glassware and filter paper.  

If the target compound (the compound that the chemist wants to further analyze or use) is the solid, vacuum filtration is the work-up technique of interest.  By using (typically) a Büchner funnel covered with filter paper and creating a vacuum, the solid is isolated and thoroughly dried on that paper.  If the target compound is in the liquid phase, instead, then gravity filtration is used, with a glass stem funnel.  Here, the filter paper catches any unwanted solid byproducts, and the liquid that passes through the paper and funnel continues into the next step of analysis or synthesis.

The goal with either type of filtration is to “compatibly / [o]btain” the target product while avoiding any additional impurities: to remove as much “extra” material as possible.  If the product is a solid, then the vacuum set-up ensures that as much liquid as possible is removed.  If the product is a liquid, then the slower gravity filtration ensures that no extra solid material is accidentally carried along.  Common objectives in the lab involve learning both techniques and discerning between their optimal uses.