Recrystallization

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

1. Preparation of the LaboratoryExpand

   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.