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,
Thioglycolic acid also used in so-called "fallout remover" or "wheel cleaner" to remove iron oxide residue from rims. Ferrous iron combines with thioglycolate to form red-violet ferric thioglycolate. Thioglycolic acid is prepared by reaction of sodium or potassium chloracetate with alkali metal hydrosulfide in aqueous medium. It can be also prepared via the Bunte salt obtained by reaction of sodium thiosulfate with chloroacetic acid: Thioglycolic acid is about 100 times stronger acid than acetic acid with a pKa of 3.83: The second ionization has a pKa of 9.3: Thioglycolic acid is a reducing agent, especially at higher pH. It oxidizes to the