And then in the next year I got two further graduate students – Ian Worrall and Peter Perkins – both great chaps, both good chemists. With Ian Worrall, I got on to the lower valence gallium compounds, which I don't want to expand, but we used Raman spectroscopy, courtesy of Len Woodward in Oxford for some of that work, and we were doing the conductivity experiments as well. With Pete Perkins I started something new. I thought if we want to understand the properties of these coordination compounds that we've been talking about, we need to know something about their thermochemistry.

As I explained earlier, you can make and break one bond – what happens to the energy of formation when you add a donor to an accepter and form a coordination compound? Now there's some tricky theoretical work that one has to do and I'm going to skip over that at the moment, but the principle thing is, I said to Pete, what we need to do is to design a calorimeter where we can study the heat of formation of coordination compounds. And we can then get some idea of the strength of donor-accepter bonds and the energetics of the process. And as these were, of course, fairly reactive compounds, obviously the reaction calorimeter that we made had to have particular properties. I don't want to go into the details of the construction, but it was a very neat piece of work that Peter Perkins did. He carried on in this work when he was at Sheffield and, in fact, he joined me later in Newcastle, but then was turning more and more to theoretical work. And when he went to a chair in Glasgow to Strathclyde, he, in fact, was by that stage, completely theoretical and made some important contributions there.