The discovery of the periodic system of the elements and the associated periodic table is generally attributed to the great Russian chemist Dmitri Mendeleev. Many authors have indulged in the game of debating just how much credit should be attributed to Mendeleev and how much to the other discoverers of this unifying theme of modern chemistry.
In fact the discovery of the periodic table represents one of a multitude of multiple discoveries which most accounts of science try to explain away. Multiple discovery is actually the rule rather than the exception and it is one of the many hints that point to the interconnected, almost organic nature of how science really develops. Many, including myself, have explored this theme by considering examples from the history of atomic physics and chemistry.
But today I am writing about a subaltern who discovered the periodic table well before Mendeleev and whose most significant contribution was published on 20 August 1864, or precisely 150 years ago. John Reina Newlands was an English chemist who never held a university position and yet went further than any of his contemporary professional chemists in discovering the all-important repeating pattern among the elements which he described in a number of articles.
Newlands came from Southwark, a suburb of London. After studying at the Royal College of chemistry he became the chief chemist at Royal Agricultural Society of Great Britain. In 1860 when the leading European chemists were attending the Karlsruhe conference to discuss such concepts as atoms, molecules and atomic weights, Newlands was busy volunteering to fight in the Italian revolutionary war under Garibaldi. This is explained by the fact that his mother was Italian descent, which also explains his having the middle name Reina. In any case he survived the fighting and set about thinking about the elements on his return to London to become a sugar chemist.
In 1863 Newlands published a list of elements which he arranged into 11 groups. The elements within each of his groups had analogous properties and displayed weights that differed by eight units or some factor of eight. But no table yet!
Nevertheless he even predicted the existence of a new element, which he believed should have an atomic weight of 163 and should fall between iridium and rhodium. Unfortunately for Newlands neither this element, or a few more he predicted, ever materialized but it does show that the prediction of elements from a system of elements is not something that only Mendeleev invented.
In the first of three articles of 1864 Newlands published his first periodic table, five years before Mendeleev incidentally. This arrangement benefited from the revised atomic weights that had been announced at the Karlsruhe conference he had missed and showed that many elements had weights differing by 16 units. But it only contained 12 elements ranging between lithium as the lightest and chlorine as the heaviest.
Then another article, on 20 August 1864, with a slightly expanded range of elements in which he dropped the use of atomic weights for the elements and replaced them with an ordinal number for each one. Historians and philosophers have amused themselves over the years by debating whether this represents an anticipation of the modern concept of atomic number, but that’s another story.
More importantly Newlands now suggested that he had a system, a repeating and periodic pattern of elements, or a periodic law. Another innovation was Newlands’ willingness to reverse pairs of elements if their atomic weights demanded this change as in the case of tellurium and iodine. Even though tellurium has a higher atomic weight than iodine it must be placed before iodine so that each element falls into the appropriate column according to chemical similarities.
The following year, Newlands had the opportunity to present his findings in a lecture to the London Chemical Society but the result was public ridicule. One member of the audience mockingly asked Newlands whether he had considered arranging the elements alphabetically s