Linus Pauling and The Nature of the Chemical Bond: A Documentary History Narrative  
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The Stochastic Secret
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Mustering everything he knew about chemistry and physics, and adding to it his new interest in model building, Pauling was able to leap to a solution where others were left mired in a swamp of confusing x-ray data.

A few years later, Pauling was describing his approach to an acquaintance, Karl Darrow, who told him that it already had a name: the stochastic method. Darrow referred Pauling to a 1909 chemistry text in which the author talked about the long-disused Greek term that could be translated as "to divine the truth by conjecture." In a simple way, the stochastic approach could be seen as nothing more than an educated guess, a hypothesis like any other scientific hypothesis. Anybody could guess at a molecular structure, and while a comparison of the molecule's properties to those calculated for the hypothetical structure might eliminate the guessed-at structure as wrong, it was difficult to say that the hypothetical structure was rigorously correct because the comparison between the guess and reality would be based almost invariably on limited experimental data.

But the way Pauling used it, the stochastic method was not a simple guessing game. You had to know enough about chemistry and crystallography to pare away all but a single structure. As he put it, "Agreement on a limited number of points cannot be accepted as verification of the hypothesis. In order for the stochastic method to be significant the principles used in formulating the hypothesis must be restrictive enough to make the hypothesis itself essentially unique; in other words, an investigator who makes use of this method should be allowed one guess."

Pauling had broken through a very complex problem using his stochastic method, and he would continue to employ it against even tougher puzzles during the next three decades. Sometimes his one guess would be wrong; far more often he would be right. This ability to "divine the truth by conjecture" would allow him to vault over his competition in solving the thorniest chemical problems. Eventually, it would bring him his greatest triumphs and earn him the reputation of a person who could almost magically dream up solutions where others had failed. But it was all the result of very hard work, deep chemical knowledge, and a willingness, a daring, to make that one guess.

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Audio Clip  Audio: Don't Be Afraid to Make Mistakes. 1997. (0:45) Transcript and More Information

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Video Clip  Video: Lecture 2, Part 9. 1957. (2:45) Transcript and More Information

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See Also: "The Determination of the Structure of Crystals with X-Rays." 1932. 

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Portrait of Karl Darrow. 1947.


Page 1
Letter from Karl Darrow to Linus Pauling. May 23, 1932.

"When Mitscherlich discovered that Glauber's salt gave a definite pressure of water vapor, he at once formed the hypothesis, that is, supposition, that other hydrates would be found to do likewise. Experiments showed this supposition to be correct. The hypothesis was at once displaced by the fact. This sort of hypothesis predicts the probable existence of certain facts or connections of facts; hence, reviving a disused word, we call it a stochastic hypothesis (Greek στοχαστικός, apt to divine the truth by conjecture). It differs from the other kind in that it professes to be composed entirely of verifiable facts and is subjected to verification as quickly as possible."

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