Google on Tuesday celebrated Danish chemist Soren Peder Lauritz Sorensen, who introduced the pH scale to the world, with an interactive Doodle.

The Google Doodle allows users to see for themselves the pH value of different food items, including tomatoes and eggs in a scale of 1 to 14.

Google Doodle, Soren Peder Lauritz Sorensen, pH scale
Soren Peder Lauritz Sorensen Google Doodle (Photo: Google)

In agriculture, the pH value can indicate the moisture associated with a soil, which can reveal what crops are suitable for the soil and what adjustments farmers must make to adapt it for growing any other crops.

Sorensen’s method of expressing acidity — the negative logarithm of hydrogen ion concentration (pH) — still has a wide range of real-world uses.

What is pH scale?

It is a measure of acidity or alkalinity of water soluble substances (pH stands for ‘potential of Hydrogen’).

The pH value is a number from 1 to 14, with 7 as the middle (neutral) point.

Values below 7 indicate acidity which increases as the number decreases, 1 being the most acidic. Values above 7 indicate alkalinity which increases as the number increases, 14 being the most alkaline.

This scale, however, is not a linear scale like a centimeter or inch scale (in which two adjacent values have the same difference). It is a logarithmic scale in which two adjacent values increase or decrease by a factor of 10.


Born in Haurebjerg in 1868, Sorensen was initially interested in studying medicine at University of Copenhagen. But he eventually spent more time studying chemistry and obtained his PhD in 1899.

Sorensen did most of his research in Carlsberg Laboratories. He became the director of its chemical section in 1901. While at Carlsberg, Sorensen started to study amino acids, proteins and enzymes.

As hydrogen ion concentration played a key role in enzymatic reactions he devised a simple way of expressing it, according to EuCheMS, the European Association for Chemical and Molecular Sciences.

He found that by taking a negative logarithm of hydrogen ion concentration a convenient scale can be established. This is the well-known pH value.

He also developed buffer solutions to maintain constant pH of solutions (Sorensen buffers), EuCheMS noted in a short biography of the scientist in its website.

Sorensen retired from his post at Carlsberg in 1938. He died in Copenhagen in 1939.

(With agency inputs)