October 19, 2005

Common Laboratory Methods

Below are definitions of common laboratory methods for purifying, separating, and transferring chemicals.

Cannulation

  • Transferring liquids or dispersed solids in solution with a tube from one flask to another, so that the materials are not exposed to air, oxygen, or moisture.

Decantation

  • Pouring the liquid off of a solution where solids have settled to the bottom, being careful not to transfer any of the solids.

Distillation

  • Using a distillation apparatus under ambient pressure or under vacuum to cause the desired product from a crude mixture to go from liquid to gas and then from gas to liquid on a cooled portion of the apparatus.

Drying

  • Removing solvents under vacuum.
  • Removing water using drying agents.

Extraction

  • Using a separatory funnel to clean a mixture by pulling impurities into either aqueous or organic phases.
  • Using a Soxhlet extraction apparatus to clean polymers or solids with a solvent that has moderate to good solubility for the impurity, but low to no solubility for the product.

Filtration

  • Using a filter to isolate solids from liquids, by pouring the mixture through it.

Lyophilization

  • Freeze drying or subliming the water out of a frozen water solution of a water soluble material.

Sublimation

  • Using a sublimation apparatus under vacuum to cause the desired product from a crude mixture to go from solid to gas and then from gas to solid on a cooled portion of the apparatus.

Trituration

  • Combination of extraction and decantation, where one scrapes and/or scratches with a stirring rod or spatula, a solid mixture in a flask that has a solvent with moderate to good solubility for the product, but low to no solublity for the impurity, or vice versa. When the solid has settled after being agitated, the solvent in decanted off and then evaporated to obtain the product, if the product was in solution. If the product was the solid, then it is dried by removing the solvent under vacuum.


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