A Separation and Purification Scheme Essay

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Abstract: Experiment 55 consists of devising a separation and purification scheme for a three component mixture. The overall objective is to isolate in pure form two of the three compounds. This was done using extraction, solubility, crystallization and vacuum filtration. The experiment was carried out two times, both of which were successful.

Background Information: This experiment combined all the knowledge of the previous labs performed throughout the semester. An unknown mixture containing an organic acid or base and an organic neutral compound in nearly equal amounts needs to be separated to its separate components. An understanding of solubility, extraction, crystallization and vacuum filtration is necessary in order to
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re and reweigh to determine amount of solid solute (Neutral compound)
• Obtain melting point
Selecting Solvent for Crystallization
• Perform the following with three 0.05g samples of unknown and the following solvents: methanol, water and toluene
• Place 0.05g unknown in a test tube
• Add .5mL solvent at room temperature to mixture o If all solid dissolves at room temp, then solid is too soluble
• If none of the solid dissolves at room temp, heat test tube and stir o Add solvent dropwise while heating and stirring until solid dissolves o If all solid dissolves, go to next step o If not, this is not a good solvent
• Remove test tube from heat and stopper it o Allow to cool to room temp o Place on ice bath o If a lot of crystals form, this is a good solvent
• Place 0.3g unknown in a 10mL Erlenmeyer flask
• Add 6mL solvent (chosen above) and a boiling stone to a 2nd Erlenmeyer flask
• Heat solvent on warm hot plat until boiling
• Add several drops of solvent, heat flask, and swirl
• Continue above step until all solid dissolves
• Remove flask and cool slowly to room temp
• Induce crystal formation by scratching inside surface of flask with glass rod
• Once room temp crystallization ceases, place flask in ice water bath
Vacuum Filtration
• Vacuum filter the crystals using a Hirsh funnel
• Moisten filter paper with a few drops of solvent and turn on water vacuum to fullest extent
• Use spatula to get crystals from bottom of flask before
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