Experimental Techniques

Experimental Techniques

1. SEDIMENTATION AND DECANTATION

   • To separate an insoluble solid from a liquid

2. FILTERATION

   • To separate insoluble solid from a liquid
   • Solid remains in the filter paper and is called residue
   • The liquid which passes through the filter paper is called filterate

3. EVAPORATION

   • Heat the mixture in an evaporation dish and the liquid evaporates leaving the solid behind

4. CRYSTALIZATION

   • This works because a solvent can dissolve less and less as its temperature rises
   • At crystalization point a solvent can dissolve no more solute
   • 1.Heat the solution to evaporate some solvent
   • 2.Test the hot solution using a glass rod
   • 3.If crystals form on the rod you know the solution is saturated
   • 4.Stop heating and leave it to cool.As it cools crystals form
   • 5.Filter crystals
   • 6.Wash them with little distilled water.Rinse and dry them with filter paper

5. SIMPLE DISTILLATION

   • The solvent boils off as a gas at its boiling point.The gas condenses back to a liquid in the condenser

6. FRACTIONAL DISTILLATION

   • Vapours of the lower boiling point liquid pass into the condenser first
   • Collect this liquid in a beaker.Stop collecting when temperature rises
   • Keep heating until vapours of the other liquid pass through the condenser
   • Collect this liquid in another beaker

7. PAPER CHROMATOGRAPHY

   • Mixtures have different substances that have different solubility and attraction to the paper they travel over
   • 1.Mark a base line on the paper with a pencil
   • The most soluble substance in the mixture travels the furthest
   • 2.Place a spot of the mixture on it
   • 3.Stand the paper upright in a beaker containing a little of a suitable solvent(water)
   • 4.Allow the solvent to rise up the paper. when it near the top remove the paper and dry it
   • 5.In case of colourless substances after drying, spray the paper with a locating agent like ninhydrin