Measuring pH: From Litmus to Glass Electrodes

Soren Sorensen invented the pH scale in 1909 at the Carlsberg brewery to control beer fermentation. Litmus paper offers a rough rainbow estimate, while a glass electrode reads hydrogen activity to two decimals. Blood sits near 7.4, and a shift of a few tenths is a medical emergency. Soil, wine, and pools all have their target windows..

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