Inventors: Duncan MacInnes, Malcolm Dole, and Otto Hopf (glassblower)
How it began: During studies by W.J.V. Osterhout on electrical properties of cells, and by Alexis Carrel on growing tissue cultures, there was a need to determine a precise measurement of acidity and alkalinity in living tissues.
What it does: The novel change from existing electrodes was determining the proper composition of a Corning glass that gave the best hydrogen probe and the most precise readings. The fragile electrode was positioned in a stand that incorporated dials to read pH directly for the first time.
Impact on medical science: This electrode was the standard laboratory instrument for measuring pH until the era of the commercial pH meter. The Beckman instrument in 1936 was based on the MacInnes-Dole glass electrode apparatus and a delicate electrometer vacuum tube to amplify the voltage from the very high resistance glass electrode.
References: MacInnes, D.A. and Dole, M. Tests of a new type of glass electrode. Industrial and Engineering Chemistry 1929, 1:57-59.
MacInnes, D.A., and Dole, M. A glass electrode apparatus for measuring the pH values of very small volumes of solution. Journal of General Physiology 1919, 12:805-811.
Photo by Lubosh Stepanek
Duncan MacInnes, Malcolm Dole, Otto Hopf, glass electrode