Experiment # 3B
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.
Safety Data & Physical Constants
Chemical Name: 95% Ethyl Alcohol
Melting Point: -130C
Boiling Point: 78C
Solubility: Miscible with water and many organic solvents
• 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.
• 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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