Hydrochloric acid is the compound with the formula HCl and is widely used as a chemical reagent. This is a strong acid that completely dissociates in water solutions forming H+ and Cl- ions. Testing the presence of hydrochloric acid is a common laboratory assignment in chemistry. Use pH paper to determine the acidity of the test solution. The common test reaction for chloride ions is the interaction with silver nitrate (AgNO3) that follows the equation HCl + AgNO3 = AgCl (precipitate) + HNO3.
Dip the piece of the pH paper into the test solution of the and quickly remove it.
Check the color of the pH paper and compare it to the color pH scale enclosed with the paper pack to assign pH of the acid solution. The paper's red color that corresponds to pH of 2 or below is indicative for hydrochloric acid.
Fill a pipette with the silver nitrate (AgNO3) solution .
Add four to five drops of the silver nitrate (ArNO3) solution from the pipette to the test solution.
Check the solution in the beaker. If a white precipitate forms, it is indicative for the hydrochloric acid solution.
Wear protective gloves and goggles when working with acid solutions.