Chem

Microscale Crystallization – Craig Tube

Experiment # 3B

Purpose

The purpose of this experiment is to introduce the technique of crystallization the most common produce used to purify crude solids in the organic laboratory.

Reaction

Safety Data & Physical Constants

      Chemical Name: 95% Ethyl Alcohol
      Formula: C2H5OH
      Melting Point: -130C
      Boiling Point: 78C
      Solubility: Miscible with water and many organic solvents

Procedure

Preparations
        • Weight 0.10g of impure sulfanilamide
        • Then transfer to a Craig tube
        • Add 2-3 mL of 95% ethyl alcohol to a small test tube with a boiling stone
        • Heat the solvent on a hot plate with an aluminum block till boils

      Dissolving the Sulfanilamide
        • Before heating Craig tube with sulfanilamide, add enough hot solvent with Pasteur pipet to barely cover the crystal
        • Then heat Craig tube with sulfanilamide until solvent is boiling
        • Add one or two drops of solvents and continue to heat Craig tube
        • Stir mixture by rapidly twirling a microspatula (10-15 sec)
        • If hasn’t dissolved add another small portion of solvent
        • Heat again with stirring until solvent boils
        • Then stir tube for 10-15 sec.
        • Continue repeating process until solid dissolved completely
        • 1st addition until the solid dissolve completely shouldn’t be longer than 10-15 min.

      Crystallization
        • Remove the Craig tube from heat
        • Insert inner plug into opening
        • Cool down Craig tube slowly by placing it into 10mL Erl. Flask
        • Gently scratch inside surface of tube with glass rod
        • Place Craig tube in an ice-water bath using beaker
        • Water and ice should be present

      Isolation of Crystals
        • Place the Craig tube in centrifuge tube
        • Decolorization Pg.663
        • Pull Craig tube out of... [continues]

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