LECTURE 4 Recrystallization 2011 SPRING - white bkg

LECTURE 4 Recrystallization 2011 SPRING - white bkg -...

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Unformatted text preview: 4/27/11 1 Announcements An extension was granted on the deadline for the Safety Quiz. Please complete your Prelab Quizzes in a timely manner, and submit them fully. No further deadlines will be extended. Announcements The midterm exam is at 7:00 PM on March 9. Locations are TBA- check Compass If you have a conflict with the exam, email me now The weeks of Feb 28 and March 7 we will not meet in the lab space. Check Compass for TBA locations Remember to finish the recrystallization quiz The recrystallization lab will take 2 weeks The lab report for TLC is due the week of Feb 8 Hot glass looks like cold glass 4/27/11 2 Recrystallization Laboratory 1 What is recrystallization? General principles: Compounds dissolve more easily in hot solvents When crystals form, they tend to exclude impurities Purification technique for solids 4/27/11 3 How to recrystallize 1. An impure solid is dissolved in an appropriate hot solvent 2. Solution is cooled causing crystals to form and impurities to stay in the solvent Solutions can become Supersaturated To induce crystallization Scratch the inside of flask with a glass stir rod Further concentrate solution (evaporate solvent) Cool solution in ice Add a seed crystal Be patient 4/27/11 4 Finding the right solvent A good solvent will: 1. Not react with desired compound 2. When hot, dissolve a large amount of desired compound 3. When cold, dissolve as little of desired compound as possible 4. Be volatile What kinds of impurities exist?...
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This note was uploaded on 04/27/2011 for the course CHEM 233 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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LECTURE 4 Recrystallization 2011 SPRING - white bkg -...

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