“Assembling set-up, distillation,
Can lead to a bit of frustration.
Be sure to securely
Clamp glassware so surely
Experiment defies ruination!”
The 9 April 2021 Twitter limerick highlighted distillation, a lab technique used in organic chemistry laboratories to purify liquid samples. The poem highlights one of the ways in which such a lab technique might go awry… and encourages students to avoid it!
“Assembling set-up, distillation, /
Can lead to a bit of frustration…”
The first semester of organic chemistry lab introduces techniques and tools one at a time, building to increasingly complex experiments in which their uses can be combined. One such technique is distillation: separating a liquid mixture into its component parts, based on differences in their boiling points.
A “simple distillation” is typically one wherein two components of a liquid mixture have boiling points distinct from one another. This mixture is placed in a round-bottomed flask, which is connected to a condenser, which is connected to a receiving flask. The mixture is heated until it reaches the boiling point of the first component; at this point, the first component vaporizes, travels as a gas into the condenser, and is condensed into the first receiving flask. (The condenser circulates cooling water through an outer jacket: within the complex set-up of the laboratory fume hood, one condenser tube connects to a faucet and the other to a drain.) Once this first component is separated out, a second receiving flask is used to collect the second component, as its own boiling point is reached.
Typically, these steps are all new for students; although they will become well-practiced with the distillation set-up, assembling it can be frustrating initially.
“Be sure to securely /
Clamp glassware so surely /
Experiment defies ruination!”
This set-up is often one of the first to involve multiple pieces of glassware– including, most notably, the condenser. To avoid “ruination” (the watery collapse of the endeavor!), it is important to clamp the pieces of glassware together and, further, to clamp everything securely within the hood itself.
Chemphasis 