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,
Casein paint or varnished for a gloss finish. The binder for casein paint is made by dissolving casein in an alkali, usually lime, ammonium carbonate, or borax. Casein itself is precipitated from milk by the action of an acid or the enzyme rennet. Lime casein works well on porous surfaces, even outdoors, though it has a short shelf-life and must be used with pigments that are balanced against the binder's low pH. Ammonium carbonate casein has similar strengths and weaknesses. Borax casein has a shelf-life of several weeks, is pH neutral, and can be used outdoors through the addition of linseed oil.