Making soluble salts

• Equipment for the first stage

  • beaker
  • gauze
  • tripod
  • heatproof mat
• Stage one


  • start with a fixed volume of a dilute acid
  • this is the limiting reactant
  • there should not be any acid remaining at the end
  • gently heat the acid until it is almost boiling
  • do not let it boil
• Stage 2

  • use a spatula to add small amounts of the oxide (reactant) to the acid
  • stir the solution using a glass rod
  • the oxide will react and seem to disappear
  • continue adding oxide if the solution continues to be clear
  • stop adding the powder once it starts to remain after being stirred
• Once the powder stops dissolving, all of the acid has reacted and the solution is now neutral
• Stage 3


  • remove the unreacted powder
  • it can be filtered out using filter paper as it is an insoluble solid
  • it is filtered using a filter funnel and filter paper
• Stage 4

  • the solution is placed in an evaporating basin
  • this is heated gently over a beaker of boiling water
  • leave this until about half the solution has evaporated and small crystals are visible
  • leave the solution in a cool place
• Stage 5


  • after 24 hours, once the crystals have formed, scrape them on a paper towel
  • gently pat them dry
  • what's left are pure, dry crystals of the salt