The encyclopedia · R&D & Science · Technical decision · 1909–1920s
Carlsberg's pH scale turned acidity into one number every chemist could read
Søren Sørensen's 1909 pH scale expressed hydrogen-ion concentration as a single logarithmic number, and it became chemistry's universal acidity scale.
Carlsberg Laboratory
The solution
In 1909 there was no widely accepted way to express hydrogen-ion concentration. Danish chemist Søren Sørensen, director of the chemical department at the Carlsberg Laboratory — funded by the brewery — introduced pH as a convenient way of expressing acidity: the negative logarithm of hydrogen ion concentration.
The move from color-change tests to electrical measurement was underway, but readings were hard to state and compare. The logarithmic scale compressed enormous concentration ranges into a compact number: neutral is around pH 7, and a change of one unit means a tenfold change in acidity or alkalinity.
Born from protein research inside a beer company's laboratory, pH became a staple of school chemistry and a universal scientific standard, used everywhere from medicine to agriculture to food science.
Why it worked
- A single number replaced awkward concentration values.
- The logarithmic scale fits the huge range of real acidities.
- Defined in an industrial lab, it solved a practical problem users actually had.
- It was simple enough to teach and use anywhere.
What can be applied
When a quantity spans orders of magnitude, a logarithmic scale turns it into one comparable number; the simplification itself is what makes the standard spread.
Aftermath
pH remains a staple of chemistry classrooms and laboratories worldwide, and its origin inside a brewery's research lab is still cited as a classic example of industry research producing fundamental science.
Sources
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