Karl Albert Hasselbalch was a physician and chemist. He was a pioneer in the use of pH measurement in medicine (with Christian Bohr

Christian Bohr

Christian Harald Lauritz Peter Emil Bohr was a Danish physician, father of the physicist and Nobel laureate Niels Bohr, as well as the mathematician Harald Bohr and grandfather of another physicist and nobel laureate Aage Bohr...

, father of Niels Bohr

Niels Bohr

Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

), and he described how the affinity of blood for oxygen was dependent on the concentration of carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

. He was also first to determine the pH of blood. In 1916, he converted the 1908 equation of Lawrence Joseph Henderson

Lawrence Joseph Henderson

Lawrence Joseph Henderson was a physiologist, chemist, biologist, philosopher, and sociologist. He became one of the leading biochemists of the first decades of the 20th century.Lawrence Henderson graduated from Harvard College in 1898 and from Harvard Medical School in 1902, receiving the M. D...

 to logarithmic form, which is now known as the Henderson-Hasselbalch equation

Henderson-Hasselbalch equation

In chemistry, the Henderson–Hasselbalch equation describes the derivation of pH as a measure of acidity in biological and chemical systems...

.