Newlands, who was born in London, studied under August von Hofmann at the Royal College of Chemistry. In 1860, being of Italian ancestry, he fought with Giuseppe Garibaldi's army in its invasion of Naples. On his return from Naples he set up as a consultant with his brother in 1864 but, after the failure of his business, worked as an industrial chemist in a sugar refinery.

In various papers published in 1864 and 1865 Newlands stated his law of octaves and came close to discovering the periodic table. He claimed that if the elements were listed in the order of their atomic weights a pattern emerged in which properties seemed to repeat themselves after each group of seven elements. He pointed out the analogy of this with the intervals of the musical scale.

Newlands's claim to see a repeating pattern was met with savage ridicule on its announcement. His classification of the elements, he was told, was as arbitrary as putting them in alphabetical order and his paper was rejected for publication by the Chemical Society. It was not until Mendeleev's periodic table was announced in 1869 that the significance of Newlands's idea was recognized and he was able to publish his paper On the Discovery of the Periodic Law (1884).