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Experiment 2- Notes.docx

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CHEM 235
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Experiment 2-Extraction (Notes) Introduction  Liquid-liquid extraction- used for separating mixture where components of mixture can be liquid or solid o Separation is based on difference in solubility of the two immiscible solvents  Liquid-Liquid extraction- 2 solvents selected must have these characteristics: a) 1 solvent preferably completely dissolve both compounds in the mixture (note: it may not work as well if one or more components was suspended in the solvent) b) 2 solvent is immiscible with 1 solvent nd c) 2 solvent preferentially dissolve only ONE component of original mixture  Mixture is dissolved or suspended in 1 solvent and then 2 solvent is introduced to solution  Using separatory funnel to shake solvent, one component of mixture will transfer to second solvent and using evaporation after, components would be separated  Partition coefficient of extraction- compound that is ndtempted to extracstwith second solvent, although it’s much more soluble in 2 solvent than in 1 , still has ability to dissolve in 1st solvent  Extraction step is repeated several times and each time removing “extracting medium” and then adding fresh portion of solvent into funnel containing original solution of mixture o This is called “successive” extractions and done to get best possible separation of components in mixture o  There must be unequal distribution of components of mixture between 2 distinct phases o With correct choice of phases, factional separation can be accomplished Operating Procedure  Separatory funnel has stopcock with 4 removable pieces (see page 2-3) o Use caution when cleaning these pieces of apparatus because extremely fragile  Suggestion of using separatory funnel 1. Always keep upright supported with ring clamp (never lay on side) 2. Stopcock grease is not required on Teflon Stopcock  Ensure assembled properly  First is white washer on stopcock plug  Then “O” ring  On the outside is lock nu  Do not sure funnel with plug tightened in stopcock o When using funnel, tighten stopcock assembly with snug o Plug will turn smoothly without sticking and will not leak when closed, if properly tightened 3. Solution is never more than 2/3 full when poured into funnel  Stopper is NEVER greased  Always rest on clean watchglass just until before use  Never keep closed separatory funnel on ring clamp 4. Stopper funnel, hold inverted, ensuring fingers of one hand is held onto closed stopcock and forefinger is on stopper  Point stem away from everyone surrounding you  Close stopcock and shake vigorously and release pressure  Repeat until no pressure develops further  Return to ring clamp and stopper removed immediately and layers are allowed to separate 5. Drain heavier bottom layer through stopcock once two layers have been separated  Top layer can be removed by decanting it through top funnel 6. Clean with plenty of hot soapy water  DOT NOT HIT stem against edge of sink  Funnel doesn’t have to be dry befor
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