In some of the work that we were doing, also had this unexpected consequence with the Apollo mission. And that is, with my access to heavy water, I thought I would test the conduction mechanisms that had been proposed for sulphuric acid by Ron Gillespie and others, and he got it absolutely right, of course, but I would check what would happen with heavy water sulphuric acid. And also anhydrous phosphoric acid... and anhydrous phosphoric acid, which I now want to say something about – is a very interesting compound. It is a very syrupy compound, its viscosity is very much greater... like treacle, really, and... or glycerol. And it has some curious properties when it melts, which I don’t want to elaborate on now, but by measuring the properties of H3PO4 phosphoric acid and D3PO4, heavy phosphoric acid, Alan Thompson, one of my graduate students in Nottingham and I, were able to establish that the conduction there went by a proton switch mechanism like it does in sulphuric acid and in water itself. The ions don’t actually move through the solution, they are working by proton switch mechanism. The detailed physical properties that we found out – the melting point of the compound, about 40 degrees, the viscosity, the density, all of these humdrum properties, we had to measure during the course of this work... and the viscosity... and they became important for the fuel cells which generated the electricity onboard the spacecrafts. I don’t want to go into fuel cells, but they need, as part of their component, phosphoric acid or some other well-conducting liquid and this is part of the fuel cell that was used.
