Which English chemist described the Law of Octaves before Mendeleev's table?

The English chemist who described the Law of Octaves before Mendeleev’s table was John Newlands.

Newlands arranged elements in order of increasing atomic weight and noticed that similar properties often recurred at intervals of eight. In 1865 he published this observation as the Law of Octaves, comparing chemical repetition with the octave in music.

His work was an important precursor to the periodic table. Newlands arranged the known elements into groups, and his scheme even suggested that undiscovered elements might exist. However, the pattern worked imperfectly with the elements known at the time, especially beyond calcium, and he did not leave systematic gaps in the way Mendeleev later did.

Newlands’ contemporaries initially ridiculed or rejected the idea, and the Chemical Society declined to publish some of his work. Recognition came later: he received the Davy Medal from the Royal Society in 1887, after Mendeleev and Meyer had already gained wider credit for periodic classification.