Mendeleev s predictions

E. Barnes, On Mendeleev s Predictions Comment on Scerri and Worrall, Studies in History and Philosophy of Science, Part A, 36 801-812, 2005 S. Schindler, Use-novel predictions and Mendeleev s Periodic Table Response to Scerri and Worrall, Studies in History and Philosophy of Science, Part A, 39 265-269, 2008 D. Harker, On the Predilections for Predictions, British Journal for the Philosophy of Science, 59 429—453, 2008 E. R. Scerri, Response to Barnes Critique of Scerri and Worrall, Studies in History and Philosophy of Science, 36 813-816, 2005. 

And Maher goes on explicitly to underline the conclusions about confirmatory weight that he sees as illustrated by this episode. He claims that Mendeleev s prediction of the existence of the third of the new elements, eka-silicon (aka germanium), was initially regarded as quite unlikely to be true but then later, with the discovery of the first two new elements (gallium and scandium), confidence in the prediction of the existence of the third new element became so high that its eventual empirical confirmation was widely regarded as a matter of course. Maher writes ... 

Maher draws attention to the 1874 paper of Lecoq de Boisbaudran in which he announced the discovery of gallium, the first of Mendeleev s predictions to be confirmed. And this is, indeed, an important paper. One possible misconception should, however, be quashed immediately. De Boisbaudran did not discover gallium as a result of testing Mendeleev s prediction. Instead he operated quite independently by empirical means in ignorance of Mendeleev s prediction and he proceeded to characterise the new element spectroscopically. De Boisbaudran s findings were published in the Comptes Rendus. 

The answer is patently no —not because of any general sceptical-philosophical scruples about induction, but because of the particular fact that the impression of consistent predictive success for Mendeleev s scheme is a complete misrepresentation of history a classic example of an effect (Mendeleev s predictive success ) created by selection-bias. Mendeleev made any number of predictions on the basis of his scheme (or rather schemes—there are at least 65 versions of Mendeleev s table, published and unpublished). Many of these predictions (depending on how exactly they are individuated)—perhaps a majority—were unsuccessful. 

After spending considerable time perusing the crumbling pages of late nineteenth-century chemistry journals and textbooks, I have confirmed the traditional account Mendeleev s periodic law attracted little attention. . . until chemists started to discover some of the elements needed to fill the gaps in his table and found that their properties were remarkably similar to those he had predicted. The frequency with which the periodic law was mentioned in-journals increased sharply after the discovery of gallium, most of that increase was clearly associated with Mendeleev s prediction of the properties of the new element, (p, 617)20... 

Firstly, although we have said it several times already, it may be as well to emphasise yet again that of course we agree that the predictive successes played an important role. As we indicated earlier, Mendeleev s prediction played no part in the actual discovery of gallium, the first new element. But in the case of scandium, the second new element, its discoverer, Cleve, remarked ... 

In addition, ft is by no means cleer that successful predictions were in bcl so decisive in the acceptance of the periodic tabic by the sciunllfic community in Mmddecv s era. For example, the Davy medal, which predates the Nobel Prize as the highest accolade in chords-try was jointly awarded to Mendeleev and Julius Lothar Meyer his leading compellor, who dkt not make aery predictions. Indeed, there is not even a mention of Mendeleev s predictions in the published speech that accompanied the joint award of the Davy prize. It therefore scons dial this prize was awarded for the manner in which the... 

The discovery of gallium was followed by the discovery of scandium (Mendeleev s eka-boron) in 1879 and of germanium (eka-sili-con) in 1886. The new elements had the approximate atomic weights and properties that Mendeleev had predicted. The scientific world was astonished. It is probably safe to say that before Mendeleev s predictions were confirmed, no chemist would have believed that the properties of unknown elements could be predicted with such accuracy. 

At about the same time that Mendeleev s predictions began to be confirmed, his relationship with his wife, Feozva, reached a low point. Because both found the situation unbearable, they decided to separate. It was agreed that Feozva would five on the couple s country estate during the academic year when Mendeleev was in St. Petersburg and that she would live in St. Petersburg when he lived on the estate during the summers. The couple s two children would stay with their mother. 

Dr. John A. Cranston. Member of the Council of the Society of Chemical Industry. Chairman of the Glasgow Section. He collaborated with Frederick Soddy in important researches on radioactivity, and is an independent discoverer of the element protactinium, Mendeleev s predicted eka-tantalum. 

Comparison of Mendeleev s Prediction and Actnal Properties for Eka-Aluminum (Gallinm)... 

Le Poidevin explains that combinatorialism is a form of reductionism about possibilia. He claims that the talk of non-existent possibilia is made true by virtue of actual objects and their properties, just as the inhabitants of model world mentioned above is made possible by virtue of a and b and the properties F and G. Presumably the reader is being invited to also consider such examples as Mendeleev s predicted elements in this way. According to le Poidevin s approach, the elements that are as yet non-existent but physically possible are those that can be regarded as combinations of some undefined basic objects and/or basic properties. 

While much of the preceding is speculative, it is no more speculative chemically than Mendeleev s predictions of gallium (eka-afuminum) and germanium (eka-silicon). The speculation centers on the possible or probable stability of nuclei with up to twice as many protons as the heaviest stable nucleus. The latter falls outside the realm of inorganic chemistry, but the synthesis and characterization of some of these elements would be most welcome. 

The success of Mendeleev s predictions showed that his ideas were probably correct. His periodic table was quickly accepted by scientists as an important summary of the properties of the elements. 

In 1966, Rochow27 somewhat criticized the accuracy of Mendeleev s predictions of the properties of eca-silicon (germanium). He stated Mendeleev predicted that mt-silicon would decompose steam with difficulty, whereas germanium does not decompose it at... 

Now for the real genius part he said that an element would eventually be discovered which would have a RAM and properties that would mean that it fitted into the gap he had left. He even predicted its properties the properties of an element that had never been seen by anyone. Only a few years later an element was discovered and given the name germanium (Ge). When its RAM was measured, it fitted exactly between gallium and arsenic. When its other properties were studied, it was found that they fitted Mendeleev s predictions with amazing accuracy (he had predicted its density to within three decimal places, for example). This and other predictions were sufficient to convince other scientists of the validity of the periodic classification of the elements, but there were still a few anomalies to be sorted out, which were not fully appreciated until 1932 when the neutron was discovered. 

Lecoq de Boisbaudran knew that the element between aluminum and indium was missing. He also knew about Mendeleev s prediction. Lecoq de Boisbaudran wanted to learn more about the spectra of elements. He thought that element number 31 might be found in zinc ores. Zinc has an atomic number of 30, so it is next to gallium on the periodic table. 

Chemists were fascinated by Mendeleev s prediction. Could he really tell them how to look for a new element And could he tell them what that element would be like ... 

He also gave these elements provisional names, such as Ekaaluminum (the prefix eka- means one beyond ) for the element that would come below aluminum. These elements were eventually discovered. As Table i illustrates, their properties were close to Mendeleev s predictions. Although other chemists, such as Newlands, had created tables of the elements, Mendeleev was the first to use the table to predict the existence of undiscovered elements. Because Mendeleev s predictions proved true, most chemists accepted his periodic table of the elements. 

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