From slags to molten salts to ionic liquids: A 50 year joyride

In the 1950's the literature on liquid silicates was mostly concerned with their function as scavengers for unwanted components in the metals extraction process. The slags were described as collections of oxide molecules. Then John Bockris, at Imperial College of Science, London, entered the scene to end this nonsense, and introduced the term "ionic liquids" for the first time. My M.Sc. Advisor in Chemical Metallurgy at Melbourne University, Mervyn Willis, told me this was the way to go, so I dropped the PbO-FeO-Fe₂O ₃-SiO₂ 4D phase diagram project I had been working on and joined Bockris' group (now at Penn) in 1956. That started a long journey through liquid silicates, molten salts, concentrated aqueous and non-aqueous solutions and back to ionic liquids, touching many personalities and countries, about which I would like to tell something. We take this opportunity to bring together in the same document, two fundamental energy level diagrams (4 decades apart in their development) that deal with the ionic liquid states of electrons, on the one hand, and protons, on the other.