One of the first things you learn in Chemistry at school is the pH scale, which measures acidity and alkalinity.

On Tuesday, Google celebrates the scale's creator, S.P.L. Sorensen.

The Danish chemist was born in Havrebjerg, Denmark, on Jan. 9, 1868. He became the head of Copenhagen's prestigious Carlsberg Laboratory in 1901, a lab created by the founder of the Carlsberg brewery mainly to advance biochemical knowledge relating to brewing.

Instead, Sorensen made a significant contribution to the field of chemistry, introducing the pH scale in 1909 as a simple way of showing the effect of ion concentration on proteins.

For those who don't remember back to Chem 101, the pH scale is the negative of the base 10 logarithm of the activity of the hydrogen ion. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic.

With his great achievement for chemistry, Sorensen died Feb. 12, 1939, aged 71.