A cotton swab is dipped into concentrated hydrochloric acid (producing hydrogen chloride gas) while a second on is dipped into concentrated aqueous ammonia (producing ammonia gas). Both cotton swabs ...

This allows it to exhibit a wide range of colors at different pH values. To Conduct Demonstration: (approx. 5 min) Show the students that the HCl solution in the Erlenmeyer is colorless. Add 10 mls of ...