Lab Manual- Appendix III for Microscale Recrystillization

Lab Manual- Appendix III for Microscale Recrystillization -...

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8/26/2010 APPENDIX III: MICROSCALE RECRYSTALLIZATION Dissolving the solute : Before you dissolve the solute, prepare a Pasteur pipette for filtering. Shorten the stem of the pipette to about 1/2", by etching the glass with a file, and snapping it while holding with a piece of cloth. Insert a tiny cotton plug into the pipette, and add a small amount of celite (~1/4" high). To a sample of the solute in a small test tube, carefully add dropwise via a pipette a small volume of hot solvent. Add a boiling chip, and maintain boiling of the solution while adding small portions of solvent. Swirl the test tube between additions to prevent bumping of the solution. Use a sand or water bath for heating. Remember the aim is to use the minimum volume of solvent to dissolve the solute . Decolorizing the Solution and Removing Suspended Solids : Remove the boiling solution from the heating bath, and after boiling has subsided, add gradually a small amount of decolorizing carbon, (Norite) (caution-frothing), and swirl the solution gently. Heat the solution to boiling, gently, for approximately 5 minutes. Record the weight of a second clean, dry, small test tube to the nearest 0.0001g. Flush the Pasteur pipette prepared above, with hot solvent, and quickly filter the hot solution into the test tube, (Fig 1). Use a small amount of hot water, to ensure complete transfer of the solution. It is important that the filtration equipment is as hot as possible, and filtration carried out quickly, otherwise, cooling of the solution may lead to crystallization and blockage of the plug in the pipette. Crystallizing the solute
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This note was uploaded on 10/27/2010 for the course CHEM 223 taught by Professor Hardin during the Fall '10 term at CUNY Hunter.

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Lab Manual- Appendix III for Microscale Recrystillization -...

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