A measure of the acidity of a solution, devised by the Danish chemist S. P. L. Sørenson in 1909.¹ It is the negative logarithm (base 10) of the hydrogen ion concentration expressed in moles per liter; the lower the number, the more acidic the solution is. By convention, pH's outside the range 0 — 14 are not used.
The concentration of an acid or base in a solution affects the solution's pH. Such concentrations are often expressed in terms of normality, which is the number of gram-equivalent weights of solute per liter of solution.
1. S. P. L Sørenson.
Enzyme Studies II. The Measurement and Meaning of Hydrogen Ion Concentration in Enzymatic Processes.
Biochemische Zeitschrift, volume 21, pages 131-200 (1909).
A lengthy excerpt is available online at www.chemteam.info/Chem-History/Sorenson-article.html
|hydrochloric acid (1N)||0.1|
|sulfuric acid (1N)||0.3|
|human gastric juice||1.3—3.0|
|baking soda in water (0.1N)||8.4|
|potassium hydroxide (1N)||14.0|
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Last revised: 21 May 2006.