How to Identify the Two Elements Combined to Form Table Salt

Table salt, also known as a rock salt or the mineral halite, consists of chloride and sodium ions. The compound has the chemical name "sodium chloride" with the formula NaCl. The classic way to identify chloride ion (Cl-) is the reaction with silver nitrate that leads to the white precipitation of silver chloride. The flame test allows you to identify the presence of sodium. Before testing, you need to dissolve the salt sample in water.

Things You'll Need

• Two beakers, 15 ml each
• Distilled water
• Spoon (optional)
• Silver nitrate (AgNO3), 0.1 molar solution
• Pipette
• Wooden splint
• Source of gas flame

Instructions

1. Pour about 10 ml of the distilled water into a beaker.

2. Add about 1 gram of the salt sample to the beaker.

3. Swirl the beaker or mix the solution with the spoon until the salt is dissolved.

4. Pour half of the solution (about 5 ml) into the second beaker.

5. Fill out a pipette with the silver nitrate solution.

6. Add 1 to 2 ml of the solution from the pipette to the first beaker. The formation of the white precipitant is indicative for chloride ions. The chemical reaction is NaCl + AgNO3 = AgCl (precipitant) + NaNO3.

7. Dip one end of the wooden splint into the solution in the second beaker for one to three seconds.

8. Wave the splint through the flame. If the color of the flame becomes bright yellow, it indicates the presence of sodium ions.

Tips & Warnings

• Use a new splint for each test.

References

• "Chemistry;" K.W. Whitten, R.E. Davis, L. Peck and G.G. Stanley; 2009
• Chemguide.co.uk: Testing For Halide Ions