That manganese and iron are associated by the strongest analogies is generally admitted, and the parallelism of nickel and cobalt is indisputable. Chromium serves to connect the ferric with the molybdic family, but appears to be more ferric than molybdic.
1857, William Odling, “On the Natural Grouping of the Elements”, in The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, volume XIII, number LXIV, page 486