PH the Hammett acidity function, "H", has been developed in connection with superacids. The concept of "unified pH scale" has been developed on the basis of the absolute chemical potential of the proton. This model uses the Lewis acid–base definition. This scale applies to liquids, gases and even solids. In 2010, a new "unified absolute pH scale" has been proposed that would allow various pH ranges across different solutions to use a common proton reference standard. Pure water is neutral. When an acid is dissolved in water, the pH will be less than 7 (25 °C). When a base, or alkali,
Dry ice color show is mixed together with the alkali present in the solution, the solution, overall, becomes neutral. HCO + H + NH + OH NH + HCO + HO (addition of ammonia) HCO + H + Na + OH Na + HCO + HO (addition of sodium hydroxide) The color of the solution changes due to the universal indicator, a pH detector. Once the alkali-to-acid universal indicator is incorporated into the solution, the color of the solution changes corresponding to the acidic color of the universal indicator. The color of ammonia and water only is green. However, once the dry ice is