From the Leiden jar to the discovery of the glass electrode by Max Cremer

The discovery of the glass electrode by Max Cremer was possible because of the advances made in the nineteenth century in understanding the electrical properties of glass, and because of the studies of electrical potential drops at the interface of phases. The discovery of the Leiden jar by E. G. von Kleist and the follow-up studies of the properties of that capacitor disclosed that glass is a dielectric. Much later, the ionic conductivity of glass was noticed and studied by J. H. Buff, W. von Beetz, W. Thomson (Baron Kelvin of Largs), W. Giese, H. L. F. von Helmholtz, E. Warburg, etc. It needed also the discovery of electromotive forces due to the partition of mobile ions (charge separation) by W. Nernst and E. H. Riesenfeld to pave the way for the idea that ion partition also occurs at solid–solution interfaces producing electromotive forces (emf). At the beginning of the twentieth century, the ground was laid to expect that a very thin glass membrane may produce an electromotive force because the glass has a finite ionic conductivity and ion partition may cause an emf. It obviously needed a physiologist like Max Cremer who desired to mimic a cell membrane (a semipermeable membrane), to use a glass membrane for that purpose. Cremer’s congenial choice of a thin glass bulb was rooted in a thorough understanding of the origin of electromotive forces, and it was not initiated directly by the Giese-Helmholtz cell, as some later reviews suggested. Later Cremer realized that an emf builds up when aqueous solutions are separated by a thin glass membrane. Cremer’s discovery was picked up by F. Haber who developed the glass electrode together with his PhD student Z. Klemensiewicz as an analytical tool. The following decades have brought improvements of the glasses and measuring techniques, and a deeper insight into the functioning of the glass electrode. Here, it will be shown that full credit for the discovery of the glass electrode effect must be given to Max Cremer. Unfortunately, his role has not been adequately described so far, mainly because Haber dominated the literature.