An Element of Order

Julius Lothar Meyer and his not-so-famous periodic table. (Yale University, Harvey Cushing/John Hay Whitney Medical Library; Edgar Fahs Smith Collection, University of Pennsylvania Libraries)

Julius Lothar Meyer and his not-so-famous periodic table. (Yale University, Harvey Cushing/John Hay Whitney Medical Library; Edgar Fahs Smith Collection, University of Pennsylvania Libraries)

The one-word difference, the shift from “periodic” to “stepwise” triggered a heated dispute between the two men that ran throughout much of the 1870s and which was extensively commented on in chemistry journals across Europe. Mendeleev knew he had to persuade the Germans, who by that time were preeminent in chemistry. In 1871 he published the full version of his work—with now detailed predictions of three new elements—in Liebigs Annalen. The battle heated up in the journal of Germany’s new chemical society, Berichte der deutschen chemischen Gesellschaft.

Mendeleev stood fast in refusing to give Meyer any credit. “Meyer’s claims for credit were modest,” Gordin says. “He wanted some credit for being part of the process of creating a periodic system. Mendeleev wanted credit for creating the system; he didn’t think he should share that with anybody. And it’s very tricky to claim that because there were so many predecessors.”

A Russian Triumph

In his fight with Meyer, Mendeleev argued that his periodic system was independent of and more advanced than anybody else’s. And he took what no one else had done, his predictions, and emphasized those, staking his claim to priority on what he called his eka-elements: eka-aluminum, eka-boron, and eka-silicon, which filled the gaps next to aluminum, boron, and silicon. Eka-aluminum was discovered in 1875 and called gallium; in 1879 eka-boron was discovered and called scandium; and eka-silicon was discovered in 1886 and called germanium. Mendeleev had expected his predictions to come true at some uncertain future date, with any luck while he was still alive. When the first of his predictions came true, Mendeleev, says Gordin, was as surprised as anyone else.

But simply predicting new elements was not enough; Mendeleev had to convince people that prediction was the important criterion in deciding who won the race. By the 1880s he had persuaded the world that prediction made the periodic system a unique chemical tool. Even so, chemists often gave Meyer and Mendeleev shared credit for the periodic system, with each discovering it independently. Meyer and Mendeleev jointly received the Davy Medal of the Royal Society in 1882. Chemistry textbooks published at the turn of the 20th century that included the periodic table often mentioned Meyer as well as Mendeleev as the creators of the periodic system.

Only death ended the priority battle. After Meyer died in 1895, Mendeleev, who died in 1907, continued to write about the priority dispute, claiming sole ownership of the periodic system, and without Meyer few were left to argue against him. The Soviet Union’s growing economic importance in the 1930s helped tip the balance further, as did the Nazi purge of German science and their expulsion of Jews, socialists, and other undesirable scientists. By the 1950s the Soviet Union was second only to the United States in terms of quantity and quality of work in chemistry, and Soviet chemistry journals referred to the periodic table as Mendeleev’s system of chemical elements. Mendeleev had become the undisputed father of the periodic table.

Dmitri Mendeleev. (Natalia Moroz)

Mendeleev After the Periodic Table

The periodic table became truly central to chemistry only after World War I, at least in part owing to the rise of the Bohr atom with its central proton nucleus surrounded by orbiting electrons. For the first time the periodic system could explain why the elements have the properties they do. Ironically, given this later importance of the electron to the periodic table, Mendeleev rejected the existence of electrons. He was also skeptical of the noble gases when they were discovered in the 1890s because they did not form bonds with other elements and so had no place in his table. Mendeleev only accepted the noble gases as a way to explain away radioactivity, which he rejected because he believed matter to be immutable.

After developing his periodic system Mendeleev moved into gas physics in search of ether and its composition. Ether was the holy grail of the physical sciences in the second half of the 19th century, and almost all scientists accepted its existence. Since ether was assumed to have mass, Mendeleev was determined to find it and place it in his periodic table among the noble gases. Not only would ether have a place at his table, he also could use it to ensure that the atom remained unbroken—no need for radioactivity or pesky electrons. Any supposed breakdown of atoms could be explained away by the emission of ether, which Mendeleev calculated to be a million times lighter than hydrogen. Some of Mendeleev’s published tables left space for ether and marked that spot with an X. He called element X Newtonium.—Michal Meyer

Michal Meyer is editor in chief of Chemical Heritage. This feature is based on a lengthy interview with Michael D. Gordin, professor of history at Princeton University, about his past and current work in the history of science.