Precipitates

Georgia Louise Williams

Precipitates

If you mix two solutions of soluble salts, the ions in the mixture can combine to form new salts. If one of the new combinations produces an insoluble salt, it will appear as a precipitate. You can use the solubility rules to work out if a precipitate will form.
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Preparing Salts

Pure samples of insoluble salts can be prepared using precipitation reactions.

  • Mix solutions of two substances that will form the insoluble salt


  • Filter the mixture. The insoluble salt will be trapped in the filter paper.


  • Wash the salt with pure water.


  • Allow the salt to dry on the filter paper. It could be dried in an oven to save time.

Barium sulfate

Barium sulfate is an insoluble salt. It is given as a 'barium meal' to patients who are going to have their stomachs or intestines X-rayed because:


  • barium sulfate is opaque to X-rays, therefore it shows up well on the X-ray picture
  • it is safe to use.
Most barium salts are toxic, but because barium sulfate is insoluble barium does not get into the blood of the patient.
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