- WHAT IS THE PURPOSE OF RECRYSTALLISATION?
- WHAT IS THE PROCEDURE OF RECRYSTALLISATION?
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Purpose: Purify an impure solid
- Dissolve the impure solid in a MINIMUM volume of an appropriate solvent
- Allow to cool and recrystallise
- Collect crystals by vacuum filteration using a buchner funnel
- Rinse with cold solvent
- Allow to dry
Check purity by melting point test
Solid must be SOLUBLE in solvent BUT insoluble when cold
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- WHAT IS THE PROCEDURE OF COLORIMETRY?
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- Choose a suitable filter (complementary colour)
- Zero/ reference with pure solvent
- Dilute 'known solution' to range of known concentrations and measure the absorbance
- Plot a calibration curve: concentration vs. absorbance
- Measure absorbance of unknown concentration solution and use calibration curve to work out the concentration
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- WHAT IS THE PROCEDURE OF USING PAPER CHROMATOGRAPHY?
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- Draw line near bottom of paper.
- Pure amino acid samples are placed on line.
- Paper is placed in a solvent in a container, making sure that the line is above the solvent.
- Place lid on top of container.
- Wait for solvent to rise and mark where it rises to.
- Spray the chromatogram with ninhydrin and heat.
- Compare Rf values.
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