Extraction
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Learning Objectives
What property is liquid-liquid extraction based on?
Liquid-liquid extraction is a separation technique based on the difference in solubility of a solute in two immiscible liquids.
What is immiscibility?
Immiscibility means that two liquids do not form a homogenous solution when mixed and partition into different phases.
In general, which phase will non-polar and polar solutes partition to?
Non-polar solutes generally partition into the organic phase, while polar solutes partition into the aqueous phase.
What is the partition coefficient?
The partition coefficient is the ratio of solute concentration in the organic layer to the solute concentration in the aqueous layer.
What property does acid-base extraction harness?
Acid-base extraction is used to extract organic compounds from an organic solvent to an aqueous phase by transforming the solute to its ionic salt phase. This makes the solute more soluble in the aqueous phase than in the organic phase.
List of Materials
Lab Prep
Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA
- Preparation of the Laboratory
Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.
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Put on a lab coat, splash-proof safety glasses, and nitrile gloves.
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Place labeled containers for halogenated waste and solid reagent waste in a satellite waste hood. Place a glass waste container nearby.
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Label a 20-mL vial as ‘unknown mixture’.
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Measure out 0.5 g of cellulose and add it to the labeled vial. Measure out 4.75 g each of benzoic acid and caffeine and add them to the vial. Stir the solids well with a glass rod.
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Tightly cap the vial and place it by the balances. Set a box of 90-mm circular filter paper by the balances. Make sure that the area has enough weighing boats, laboratory wipes, and clean spatulas.
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Set out the following glassware and equipment at each student lab station (we suggest that students work in pairs):
1 Lab stand with ring fixture 1 Hotplate 1 Vacuum pump (or house vacuum) 1 Medium 3-prong clamp 1 125-mL separatory funnel with a stopper 1 125-mL Erlenmeyer flask 3 10-mL glass graduated cylinders 2 50-mL glass graduated cylinders 2 50-mL beakers 3 100-mL beakers 1 600-mL beaker 1 250-mL filter flask 1 Büchner funnel 2 60-mL glass funnels 2 100-mm watch glasses 2 Glass stirring rods 2 24/40 rubber adapters 2 Pasteur pipette bulbs 2 Small spatulas 1 Package of pH paper 1 Roll of lab tape and pen -
Distribute boxes of lab wipes and Pasteur pipettes around the lab so that each workstation has them nearby.
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Set out anhydrous magnesium sulfate, sodium bicarbonate, vacuum grease, and several spatulas on a common bench.
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Shortly before the lab, place labeled bottles of dichloromethane and 1 M NaOH in a fume hood.
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Put a bottle of 3 M HCl in a separate fume hood to avoid inadvertent contact between acids and bases.
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