In 1883 Smithells was appointed assistant lecturer at Owens College. Two years later he succeeded Professor Sir Edward Thorpe as Professor of Chemistry at the Yorkshire College, Leeds, which became the University of Leeds in 1904. Smithells went on to be Pro-Vice-Chancellor at Leeds, a post he held until he retired from his Chair as Emeritus Professor in 1923.
During his career Smithells was Honorary Educational Adviser on Home Science and Household Economics to King's College London (appointed 1907), President of the Society of British Gas Industries (1911).
In 1923 he became Director of the Salters’ Institute of Industrial Chemistry a role that involved assessing applications for grants, he remained a director until 1937.
His research was predominantly focused on flames, the process of burning and flame spectroscopy[2][3][4]
As well as being a Fellow of the Royal Society (elected 1901, becoming vice-president in 1916), he was also a Fellow of the Institute of Chemistry (elected 1887) serving on the Council and holding the posts of Vice-president from 1915-1917, 1923-1926 and 1930-1933 and President (1927-1930), and was made an Honorary Fellow of the Society for Analytical Chemistry (elected 1927).
^Smithells, Arthur; Whitaker, Henry; Holmes, Theodora (1930). "XXV. - The influence of hydrogen and of water vapour on the ignition of carbon monoxide". Journal of the Chemical Society (Resumed): 185–194. doi:10.1039/JR9300000185.
