Lecture 2 - Recrystallization - Before next week’s lab...

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Unformatted text preview: Before next week’s lab you should… Before next week’s lab you should… • Complete Melting Points pre-lab quiz • Write up Pre-Lab report in your notebook: – Melting Points – Recrystallization • Use Lab Notebook handouts available online • Bound manuals available mid-week next week • Reminder: We are unable to re-open quizzes • Computer issues, etc., are your responsibility • Lab goggles must be worn AT ALL TIMES! Three samples of the same compound... How can you determine which is the most pure? 1) Take the melting point . 2) Compare the color . 3) Compare the crystal size . brown white grey medium large small Can anyone guess the identity of this compound? What is rock candy? • Rock candy is the purest form of sugar available. • A hot, supersaturated solution of cane sugar and water is poured into large tanks. • This heating process busts apart the molecular crystal lattice of the sugar (sucrose), freeing any impurities. • Under carefully controlled conditions, the molecules of sucrose rejoin during the cooling process , this time, excluding the impurities . • This allows the formation of larger, purer crystals which are subsequently (and deliciously) harvested as Rock Candy. Information and photographs courtesy of Dryden & Palmer Rock Candy, http://www.rockcandy.com “Rock candy is recrystallized cane sugar.” Recrystallization • The process of recrystallization involves (1) Dissolution of the solid in an appropriate solvent at an elevated temperature , followed by (2) subsequent re-formation...
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This note was uploaded on 09/14/2009 for the course CHEM 233 taught by Professor Miller during the Winter '08 term at University of Illinois at Urbana–Champaign.

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Lecture 2 - Recrystallization - Before next week’s lab...

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