Fractional Crystallization

1
Fractional Crystallization
General Chemistry 101/102Laboratory
ManualUniversity of North Carolina at Wilmington
2
Fractional Crystallization

• Purpose

• Use the technique of vacuum filtration to
  separate a heterogeneous mixture into its
  components.
• Use the technique of fractional crystallization
  to separate a homogeneous mixture into its
  components.

• Safety Considerations
• Exercise care not to burn yourself on hot
  ringstands, rings, and beakers.
• Dispose of all waste materials in the
  appropriately labeled containers in the hood.

3
Fractional Crystallization

• Procedure

• Add about 25 g of one of the unknown mixtures to
  a pre-weighed 250 mL beaker. Weigh the beaker
  and mixture to determine the mass of the mixture.

• Add 60 mL of DI water to the beaker and heat the
  mixture to 85 ºC (do not allow it to boil) while
  stirring. Keep the mixture near 85 ºC for 5
  minutes with stirring.

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Fractional Crystallization

• Procedure

5
Fractional Crystallization

• Procedure

• Pour the filtrate into a clean 250 mL beaker and
  save it for the recrystallization.

• Transfer the sand and filter paper to a
  pre-weighed watch glass and allow the sand to
  finish drying.

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Fractional Crystallization

• Procedure

7
Fractional Crystallization

• Procedure

• Wash the borax crystals with a 10 mL portion of
  ice water. Continue the suction for 3-4 minutes
  to help dry the crystals.

• Transfer the borax crystals and filter paper to a
  pre-weighed watch glass. Determine the mass of
  the borax crystals.

8
Fermentation and Distillation

• Procedure