Specification Point 2.39:
Describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an insoluble reactant

Preparation of  Soluble Salts

Using Dilute Acid and Insoluble Base:

Preparation of soluble salts, CIE IGCSE Chemistry

The filtration of the mixture to remove the excess base


  • Add dilute acid into a beaker and heat using a bunsen burner flame
  • Add the insoluble base, a little at a time, to the warm dilute acid and stir until the base is in excess (i.e. until the base stops disappearing and a suspension of the base forms in the acid)
  • Filter the mixture into an evaporating basin to remove the excess base
  • Heat the solution to evaporate water and to make the solution saturated. Check the solution is saturated by dipping a cold, glass rod to the solution and seeing if crystals form on the end.
  • Leave the filtrate in a warm place to dry and crystallise
  • Decant excess solution
  • Blot crystals dry

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.