In chemistry, pH is a measure of the activity of the (solvated) hydrogen ion p[H], which measures the hydrogen ion concentration. This is closely related to, and is often written as, pH Pure water which has a pH very close to 7 at 77 °F. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. Measurement of pH for aqueous solutions can be done with a glass electrode and a pH meter, or using indicators.
The term Acidity is often used as a sensory term to describe flavor profiles for coffee, tea, wine and many other culinary ingredients. This term shouldn’t be confused with Acid level measures in pH.
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