Humphry Davy was an English chemist and a professor of chemistry at the Londons Royal Institution in the early 1800s.  There he performed experiments that cast doubt upon some of Lavoisiers key ideas such as the acidity of oxygen and the idea of a caloric element.  Davy was able to show that acidity was not due to the presence of oxygen using muriatic acid (hydrochloric acid) as proof.  He also proved that the compound oxymuriatic acid contained no oxygen and was instead an element, which he named chlorine.  Through his use of electric batteries at the Royal Institution Davy first isolated chlorine, followed by the isolation of elemental iodine in 1813.  Using the batteries Davy was also able to isolate the elements sodium and potassium.  From these experiments Davy concluded that the forces that join chemical elements together must be electrical in nature.  Davy also opposed the idea that caloric was an immaterial fluid, arguing instead that heat was a type of motion.