In 1894 he became a chemistry master at
Dulwich College, spending some twenty years in teaching and research, and for a short time (1902–1904) was headmaster of
Alleyn's School, Dulwich. During this time he was elected to a Lee's Readership at
Christ Church Oxford, becoming responsible for inorganic chemistry lectures at the university. In 1912 he was appointed Professor at
Imperial College, replacing Sir T. E. Thorpe as Director of the Chemistry Department; here he remained until retiring in 1932. He conducted pioneering studies on the effects of drying on chemicals and the catalytic effect of moisture in chemical reactions. According to his 1902 FRS application citation he proved that "dry carbon and phosphorus will not inflame when heated in dry oxygen; that dry ammonia and hydrogen chloride when mixed do not unite, and that dry
ammonium chloride and
calomel respectively vaporise without dissociation... [and that] dry hydrogen and oxygen mixed together are not ignited by exposure to the temperature of melting silver". He also claimed that complete drying has the effect of significantly raising the boiling temperature of chemicals, but reproducibility of the results could not be achieved. During WWI Baker was appointed scientific adviser to the War Office. He worked with his father-in-law in the development of specially resistant glass for the contact
‘horns’ of submarine mines.
Whitefriars Glass produced 600,000 of these glass horns, individually testing them at extremes of temperature, before dropping them to test their strength. ==Family==