Langmuir 1989,4539-539
539
Notes C8SC Folklore. 1. Whatever Happened to the Stern of t h e Stern Layer?'
Karol J. Mysels
Chemistry Department, Uniuersity of California, San Diego, La Jolla, Californio 92093-0317 Received September 29, 1.W Briefly thank you,he has always been doing very well, including a free trip to Stockholm.
The Article
Stem's seminal 1924 article' on the structure of the double layer is nine pagea long and still makes good reading (in German). I t begins by examining critically the condensed Helmholtz model and the diffuse Gouy-Chapman model and then proposes the new picture in which the counterions are in part adsorbed on the suface and in part free to form a diffuse charge. In a footnote he notes that a conversation revealed that Volmer and Cassel have independently come to the same concept of the double layer. Stern then develops some quantitative aspects of his model, particularly the relation between the electric capacity and the adsorption potentials of the ions. He includes the case of charge reversal by strongly adsorbed counterions. Finally, there is a brief discussion of electrokinetic potentials in which Stem argues, unfortunately, that they can be taken as equal to the Stem layer potentials. The emphasis of the whole article is on the mercury/ water interface with only brief reference to the glass surface. The surfaces are always assumed to be tlat, and there is no mention of the particles or colloids, where Stern's ideas found such a fertile field later. The article is very well written, with assumptions clearly stated, including those of smeared charges, of constancy of adsorption potentials, and of simplification in the choice of distances for the adsorbed and the diffuse layers. This seems to be the only article of Stern relating to the double-layer subject. His interests were mainly in the area of mo@cular beams. Otto Stern B p 101yeam ago in German Siesia, Stem was 36 years old when he wrote his article. He had just been appointed full (Ordinarius) professor of physical chemistry a t the University of Hamburg. This was 12 years, including war-time military service, since he received his Ph.D. a t 24 from the University of Breslau and became Einstein's assistant in Prague and then in Zurich. They published a joint paper on zero point ene1gies.l 'Editors comment. This short paper fills in a bit of interesting history. It seemed to me that it would add to the collegial atmcsphere of the Longmuir family of authors and readers.
0743-7463/89/2405-0539W1.50/0
Fgure 1. Otto Stern around 1930. Photo of her uncle courtesy of Liselotte Templeton.
He held teaching positions in theoretical physics in Zurich, Frankfurt, and Rostock before a 10-year stay a t Hamburg. He seems to have had an active school there, which included as postdoctorial students E. G.Segre and I. I. Rabi, both later Nobel Prize winnen. Forced to leave Germany in 1933, Stern became research professor of theoretical physics a t the Carnegie Institute in Pittsburgh, PA, until his retirement in 1945. He died in 1969 in Berkely, CA.
The Trip to Stockholm This came shortly before his retirement when he was awarded the 1943 Nobel Prize in physics for developing the famous Stern-Gerlach experiment, which showed, by the splitting of a beam of silver atoms in a divergent magnetic field, that their magnetic moment was quantized. The original concept of this experiment was described by Stern in 19213after he had already started the experimental work with Gerlach. This continued after Stern moved to Rostock (jointly during the Christmas vacation and then by Gerlach alone), and the first success was reported in 1922.' Thus, as the dates indicate, it was not the Stem of the Stern layer who did the Stern-Gerlach experiments but the Stem of Stem-Gerlach fame who thought of the Stem layer. (1) Stem. 0. Z. Efeklmchem. 1924, So. 508 (2) Einstein. A,; Stem,0. Ann. Phys. 191.?,40,551.
(3)Stern, 0. 2. Phys. 1921.7,249. (4) Gerlach. W.; Stem. 0. Z. Phys. 1922.9. 349.
0 1989 American Chemical Society
