0 Copyright 1985 American Chemical Society
SEPTEMBER/OCTOBER 1985 VOLUME 1, NUMBER 5
Editorial A brief editorial comment is indicated as we approach the end of our first year of publication. Langmuir is now a going operation and is following closely the objectives described in the first issue editorial, with respect both to content and to quality. We owe thanks to the good authors who have submitted papers; we are very grateful for the effective effort of reviewers who, in general, have been cooperative and prompt in their duties. As an indication of general organizational effectiveness, the median publication time of papers is about four months (from receipt of a final manuscript); that for letters is about three months. Subscriptions, both member and institutional, have exceeded the forecast. The Editorial Advisory Board has provided valuable advice and much active participation. We have continued the practice of having a get-together of those members attending national ACS and other relevant meetings and
symposia. There has been much exchange of information and of opinion. Key ACS publications staff join us and an excellent liaison between editorial and production aspects has been maintained. The first issue contained an Appreciation of the scientist Langmuir, after whom the journal is named. We have followed the suggestion of some Editorial Advisory Board members that similar critical biographies be published of other persons who have made notable contributions to surface/colloid chemistry. Following this editorial is an interesting account of another great man, Einstein. The author of this contribution has devoted much time and thought both to Einstein the man and to Einstein the scientist; his Appreciation is very perceptive. Arthur Adamson
Editor
Why Not “Einstein”! When Arthur Adamson asked for a follow-up to Karol Mysels’ essay,’ “Why “Langmuir”?”, which would treat Einstein’s connections to colloid science, I realized that the question raised above must be punctuated so as to be rhetorical. Even so, the question is not far-fetched. Indeed I’ve often twitted my friends in physics by observing that Einstein really was a colloid chemist since his Ph.D. thesis dealt with a fundamental problem of colloid science. Einstein came to colloid science from his early interest in statistical thermodynamics, which resulted in 40 papers published during the first quarter of this century. There is a general acquaintance with the broad outlines of Einstein’s life so that a biographical review is superfluous. The recent biography by Pais2 has been acclaimed to be most perceptive, and its definitive treatment of Einstein’s scientific work, including that on colloids, is quite detailed. I will borrow from it heavily. The issue of the reality of atoms and molecules was far from resolved at the turn of this century with physicists like E. Mach and chemists like Wilhelm Ostwald and J. H. van’t Hoff among the most determined sceptic^.^ (1)Mysels, Karol J. Langmuir 1985,1, 2. (2)Pais, A. “‘Subtle is the Lord ...’ The Science and the Life of Albert Einstein”; Oxford University Press: New York, 1982.
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Einstein himself wrote2“...I developed statistical mechanics and the molecular-kinetic theory of thermodynamics based upon it. My main purpose for doing this was to find facts which would attest to the existence of atoms of definite size.” In one sense the quest for a manifestation of atomic and molecular reality can be reduced to a determination of Avogadro’s number N since this provides a measure of the mass of an atom. Einstein’s statistical analysis, in a series of papers starting in 1905, that the Brownian movement of a colloidal particle was a manifestation of bombardment by the fluid molecules permitted estimation of N by three techniques-translational Brownian movement, rotational Brownian movement, and sedimentation equilibrium. Subsequent experimental studies that led to accurate estimations of N were recognized by the awards in 1926 of the Nobel Prize in Physics to Jean Perrin4 and that in Chemistry to The S ~ e d b e r g . ~ (3) Kerker, M. J. Chem. Educ. 1974,51, 764. Among the many references cited here, particular attention is drawn to the collection: Fiirth, R. “Investigations on the Brownian Movement”; Cowper, A. D., Translator; Methuen: London, 1926 (reprinted by Dover Publications: New Vork). - ___,_ (4)Nye, M. J. “Molecular Reality”; Elsevier: New York, 1972. (5) Kerker, M. Isis 1976,67,190.
0 1985 American Chemical Society
532 Langmuir, Vol. I , No. 5, 1985
Although the Brownian movement work was published first, Einstein’s Ph.D. thesis and the 1906 paper based on it were prior. Indeed Pais feela that the first 1905 Brownian movement paper is a sequel to the thesis. Pais exults over it; “Quite apart from the fundamental nature of some results obtained in the thesis, there is another reason why the paper is of uncommon interest: it has led to more widespread practical applications than any other paper Einstein ever wrote... Of the eleven scientific articles published by any author before 1912 and cited most frequently between 1961 and 1975, four are by Einstein. Among these four, the thesis (or, rather, the 1906 paper) ranks fmt; then follows a sequel to it-..written in 1911. The Brownian movement paper ranks third, the paper on critical opalescence fourth.” In his thesis Einstein utilized conventional bydrodynamics to derive an equation for the viscosity of a fluid containing the volume fraction 4 of spheres dispersed in a fluid of viscosity 9
.
1)’
= ?(I + 0)
which in 1911 he corrected to the now famous 9’ = ~ ( l2.54)
+
By assuming that the system obeys van’t Hoffs law and utilizing Stoke’s law for the fictional mistance of a sphere moving through an incompressible fluid, Einstein derived an expression for the diffusion constant 1 D = -RT N 6mp which permitted him, using data on sugar solutions, to estimate that N = 6.6 X loa. Einstein invented still a fifth technique for determining N from light scattering hy both pure liquids and solutions. He attributed light scattering to density fluctuations on the molecular level and thus a manifestation of the thermodynamic properties. This has led to the recent techniques promoted by Peter Debye for the absolute determination of the molecular weight of macromolecules. Light scattering (1910) was Einstein’s last major work on classical
statistical physics. He was then to devote his efforts to general relativity. There can be no argument that Einstein’s main interests and contributions were in quantum theory and relativity. Yet even though colloid science comprised a smaller part of his outout. Einstein’s work on colloids has had a maior impact. And remember, the subject of his Pb.D. thesis was colloid science! Milton Kerker Clarkson University .
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