Google's latest Doodle - on Tuesday - paid rich tributes to Danish biochemist Søren Peder Lauritz Sørensen who is credited to have been the first to introduce the concept of pH.
pH is a scale for measuring acidity and alkalinity of a substance, and stands for power of hydrogen.
While now it is commonly referred to in cosmetic products among other items, it was first introduced by Sørensen. Born in 1868, Sørensen first introduced the concept of pH in 1909 for simplifying the manner in which the acidity and alkalinity of products can be described.
In its doodle tribute to him, users can play a small quiz with random products to be placed according to their pH levels. A caricature of Sørensen provides 'mentoring' and either shows a thumbs up or shakes his head depending on whether the products are categorised right or now.
