01-09 Søren Sørensen and the pH scale

"Today in chemistry history" graphic for 9th January, marking Danish chemist Søren Sørensen's birthday in 1868 and his invention of the pH scale. Sørensen came up with the pH scale to measure hydrogen ion concentrations in solutions while working at the Carlsberg research lab in Copenhagen. The pH scale runs from 0 to 14 and is a way of measuring how acidic or alkaline a solution is. It’s a logarithmic scale, so a change of one represents a ten times increase or decrease in acidity or alkalinity. A neutral solution has an equal concentration of hydrogen and hydroxide ions; this is usually at pH 7, but can vary slightly depending on temperature.