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Abstract

Protocol

Representative Results

Materials

Chemistry

Recrystallization

Published: Not Published

  1. Preparation of the Laboratory

    Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.

    • To set up for this lab experiment, wear the appropriate personal protective equipment, including a lab coat, chemical splash goggles, and gloves.
    • Confirm that the lab has a glass waste container and a container for solid acetanilide and trans-cinnamic acid waste.
    • Prepare 40 mL of a 95% by volume ethanol solution. Measure 38 mL of absolute ethanol and pour it into a 50-mL glass bottle using a funnel.
    • Then, add 2 mL of deionized water to the bottle. Mix the solution with a glass rod or by shaking the closed bottle until it appears homogeneous.
    • Label the bottle and place it in a fume hood for solvents. Store the absolute ethanol in a cabinet for flammable materials.
    • Set aside high-purity acetanilide and trans-cinnamic acid to be used as seed crystals.
    • Bring reagent-grade acetanilide and trans-cinnamic acid to the balances for students to use. Confirm that there are enough lab wipes, spatulas, and weighing boats.
    • Set out the following glassware and equipment at each student lab station:
       1    Lab stand
       1    3-prong clamp
       1    Stirring hotplate
       1    Pair of flask tongs
       1    Vacuum pump (or house vacuum)
       1    125- or 250-mL filter flask
       2    Büchner funnels
       1    Filter adapter
       2    600-mL beakers
       1    250-mL beaker
       2    5-mL graduated cylinders
       1    10-mL graduated cylinder
       1    125-mL Erlenmeyer flask*
       1    25-mL Erlenmeyer flask
       2    Glass stirring rods
       1    Medium stir bar
       1    Pair of tweezers
       2    Pipette bulbs
      *Note: Try to use older flasks with scratches on the inside for this lab.
    • Keep extra 125-mL Erlenmeyer flasks, stemless or wide-stem glass funnels, large filter papers, small beakers, and boiling chips available in case students need to hot filter their acetanilide solutions.
    • Place boxes of laboratory wipes, medium filter papers, and Pasteur pipettes in a central area for the students.
    • Set up the melting point analyzer and place a container of capillaries next to it.
    • Just before the lab, fill an insulated cooler with about 8 L of crushed ice. Place the cooler and an ice scoop on the central bench in the lab.

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What is recrystallization used for?

Recrystallization is a method to purify solid compounds based on the differences in solubility in a solvent.

What are the steps of recrystallization?

1-Choosing the solvent or solvent pairs, 2-dissolving the sample in the minimum volume of the hot solvent, 3-cooling the saturated solution, 4-collecting and washing the crystals, and 5-drying.

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  • Lab stand
    5
  • 3-prong clamp
    5
  • Stirring hotplate
    5
  • Flask tongs
    5
  • Vacuum pump or house vacuum wih tubing
    5
  • 125- or 250-mL glass filter flask
    5
  • Büchner funnel
    10
  • Filter adapter
    5
  • 600-mL glass beaker
    10
  • 250-mL glass beaker
    5
  • 5- or 10-mL glass graduated cylinder
    10
  • 10-mL glass graduated cylinder
    5
  • 125-mL Erlenmeyer flask
    10
  • 25-mL Erlenmeyer flask
    5
  • Glass stirring rod
    10
  • Medium stir bar
    5
  • Metal tweezers
    5
  • Pasteur pipette bulb
    10
  • Melting point capillary tube
    20
  • Glass funnel with small stem
    5
  • Boiling chips
    10
  • 50-mL glass beaker
    5
  • Acetanilide (99% purity)
    20 mg
  • Acetanilide (>99% purity)
    20 mg
  • trans-cinnamic acid (98% purity)
    20 mg
  • trans-cinnamic acid (>99% purity)
    20 mg
  • Ethanol, absolute
    100 mL
  • 50-mL glass bottle with solvent-resistant cap
    1
  • 50-mL glass graduated cylinder
    1
  • Glass funnel
    1
  • Pasteur pipettes
    -1 Dependent on lab size
  • 70-mm filter paper
    1 box
  • 110-mm filter paper
    1 box
  • Analytical balance (at least 1)
    -1 Dependent on lab size
  • Weighing boats
    -1 Dependent on lab size
  • Spatulas
    -1 Dependent on lab size
  • Melting point analyzer (at least 1)
    -1 Dependent on lab size
  • Deionized water
    -1 Dependent on lab size
  • Crushed ice
    -1 Dependent on lab size
  • Ice container
    -1 Dependent on lab size
  • Ice scoop (minimum 1)
    -1 Dependent on lab size
  • Lab wipes
    -1 Dependent on lab size

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