Collie served as Professor of Organic Chemistry at UCL from 1896 to 1913, and headed its chemistry department from 1913 to 1928. He performed important research that led to the taking of the first x-ray for diagnosing medical conditions. According to Bentley, Collie "worked with Ramsay on the inert gases, constructed the first neon lamp, proposed a dynamic structure for benzene, and discovered the first oxonium salt." The work on neon discharge lamps was conducted in 1909. The effect of glowing neon in contact with mercury was later sometimes called the Collier effect.