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Letters from our readers
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Planck and chemistry |
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| I am writing in response to the excellent article, “Planck’s quantum theory and the laws of chemistry”, by Weldon Vlasak, which appeared in the July issue of Chemical Innovation. I have always had an interest in the origins of quantum theory because it is, in relation to the previously accepted laws of physics, so counterintuitive, even radical. Because of this, I’ve always taken an interest in the kind of minds that could propose such ideas. Mr. Vlasak was correct in his assertion that modern science textbooks are somewhat lacking in basic information regarding the fundamental research as well as the kind of thought processes that must have occurred for these ideas to take shape.
Max Planck has always been my favorite chemist–physicist because he was a very conservative thermodynamicist. (I think one would have to be rather conservative to work in thermo.) Dr. Vlasak did an excellent job of describing Planck’s painstaking attention to detail, his dedication to balancing scientific theories with reality, and his meticulous documentation. However, I think that he missed a very important point, or at least did not give it enough emphasis. Planck did something very out of character to get the explanation of blackbody radiation to work. He took something of a leap of faith by proposing the quantization of energy states, and was, by all accounts, rather uncomfortable with it all. I’m not certain whether it was an act of desperation, or if he really figured it would all work out in the end, but I’ve read an account that that suggested Planck himself did not actually believe that energy states were quantized (1). I’ve always concluded that he went about his research hoping the constant would eventually just cancel out. So, Planck’s going out on a limb to present this model before the Berlin Physical Society was not only extraordinary with respect to the proposal itself, but especially so when one considers that it was Planck who proposed it. In any case, I thoroughly enjoyed this article. It fits nicely in your publication, being an extreme case of “chemical innovation”. I look forward to the final chapter that was promised for a future article. Kimberly E. Engle Reference
The author replies: Planck’s analysis depended totally on the quantization of the energy states of molecules that were defined by the correspondence with the measurements of the thermodynamic reactions of chemical processes. He referred to the lifetime efforts of Ludwig Boltzmann, who believed that probability processes were fundamental to thermodynamic reactions, and Rudolf Clausius, who established the fundamental concept of entropy. Planck associated the energy states that were defined in the thermodynamic equation for chemical reactions with “events” and “transformations of energy”. He used the term “preference of nature for a given state”, saying, “nature prefers the more probable states to the less probable, because in nature processes take place in the direction of greater probability.” As stated in the article, Planck said that the homogeneous “states” of the thermodynamic equation must be related to a finite number of equally likely configurations in which the state may be realized. Ms. Engle also referred to a “constant”, saying that Planck hoped that it “would eventually just cancel out”. There are two important constants that are present in his famous radiation equation. He went through a careful and extensive process to first determine that a constant (–1), not present in Wien’s equation, appears in the denominator of the equation that he derived. Correlating this result with known measurements of chemistry and physics, he was then able to determine the value of the constant, h, now known as Planck’s constant. In a second article on this subject, soon to be published, I will give a more detailed description of these methods and how Planck successfully applied his state theory to radiant heat (in his terms, “the state of radiation”). Weldon Vlasak |
