May 29 (UPI) -- Google is honoring Danish chemist Soren Peder Lauritz Sorensen with an interactive Doodle that quizzes users using the pH scale.
The pH scale, invented by Sorensen in 1909, is used to test how acidic or alkaline a substance is. The pH represents the concentration of positively-charged hydrogen ions in a solution.
Google's homepage, which features an illustration of Sorensen, tasks users with deciding if everyday food items such as tomatoes, lemons, eggs and broccoli would be classified as acidic or alkaline.
An acid is any chemical that releases positively-charged hydrogen when mixed with mater and is corrosive to some metals while alkalis release negatively-charged ions called hydroxyls, which are made up of a hydrogen and an oxygen atom and can dissolve some organic substances.
The scale is important in helping to treat soil, reduce tooth decay and in monitoring the acidity of water.
Sorensen studied at the University of Copenhagen where he wanted to study medicine before switching over to chemistry. He ran the Carlsberg Laboratory in Copenhagen until 1938, a year before his death in 1939.