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Metric: pH

Range: 0-14 (no units)

Measures: Degree of acidity or alkalinity. It is a logarithmic scale expressing the concentration of Hydrogen ions in solution.

pH = -log10 [H+]

A solution is “acidic” if pH is less than 7 (Hydrogen ion concentration is greater than 10−7 M), “neutral” if pH equals 7 (Hydrogen ion concentration equals 10−7 M), and “alkaline” if pH greater than 7 (Hydrogen ion concentration is less than 10−7 M). As was pointed out here, pH measures intensity and not capacity. This is similar to temperature, which is actually a measure of how hot something is and not the amount of heat carried by a given material. Or, as another example, People Magazine’s “Sexiest” issue measures a given star’s allure and not his or her sexual prowess (Richard Gere – handsome man, requires gerbil-related stimulation).

History: The pH scale was originally described in 1909 by Soren Sörenson, also known for his position near the end of the line when names were being handed out. Demonstrating the niceties of chemistry to his young son (Soren II), Sörenson spilled concentrated ammonia on his hand. He started to scream “Fff–” but stopped short, remembering that his impressionable child was standing next to him. When asked what was wrong, Sörenson told his son through clenched teeth that the liquid daddy spilled on himself was high on the “Ffff” meter. The recent invention of the telephone (where “ph” first could be pronounced “Fff”) gave rise to the name we currently use. The pH scale has seen widespread application over the years. It is a subject of obsession at various skin care conglomerates and at your friendly neighbourhood grow-op.

Planning for 2009’s “pH Centennial Celebration” is well underway.

Related quote:
“Tune in, turn on, drop out” – Timothy Leary (on acid)

Use of “pH” in a sentence:
“In the hip hop lexicon, ‘phat’ is spelled with a pH.”