How to Detect Anions in Salt Samples

Detecting anions in salt requires mixing ionic compounds and using your sense of sight and smell. An anion is a negatively charged ion. An ion is an atom with a positive or negative charge. Some examples of anions are nitrate, phosphate and carbonate. Table salt is made of positively charged sodium ions and negatively charged chlorine ions. You can detect the presence of anions by adding ionic compounds like sulfuric acid and barium chloride to a salt solution.

Things You'll Need

  • Test tube
  • Beaker
  • Sulfuric acid
  • Salt
  • Lime water
  • Iron sulfate
  • Chemical paper
  • Starch paper
  • Blue litmus paper
  • Barium chloride
  • Nitric acid
  • Ammonium molybdate
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Instructions

  1. Find Anions in Salt

    • 1

      Add sulfuric acid to salt. Note the presence of carbon dioxide if a colorless gas turns lime water milky. Note the presence of nitrogen dioxide if reddish brown fumes turn iron sulfate black. Sulfur trioxide is present if a colorless gas turns potassium dichromate chemical paper green. Sulfur is present if the combination smells like rotten eggs.

    • 2

      Add sulfuric acid to salt. Carbon is present if a colorless white gas produces white fumes when a glass rod is dipped in ammonia and bought to the mouth of the test tube. Bromine is present if reddish brown vapors turn starch paper yellow. Iodine is present if deep violet vapors turn starch paper blue. Acetate is present if colorless vapors with a vinegar smell turn blue litmus paper red. Nitrate is present if reddish brown gas turns an iron sulfate solution black.

    • 3

      Add barium chloride to a salt solution. Sulfate is present if sulfates give a white precipitate that is insoluble in any acid or base. To the salt extract add ammonium molybdate. The presence of phospate gives an ammonia crystalline precipitate upon adding nitric acid and ammonium molybdate.

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