So the big question was the temperature range, up to what temperature could we extend the measurements? As I say, you heat up the vessel and you record the temperature and, of course, Eucken wanted to get as far as possible because it's more information. So we had a conference with his assistant who suggested, he said, 'I wouldn't go much above 150°C, that yields a pressure of 5 atmospheres and a glass vessel wouldn't stand more than that'. 'Oh', Eucken said, 'what nonsense! I could go up to 200°C, but that would be over 10 atmospheres pressure'. Well, so I was left with a decision, how far to go?

So my first experiment, I decided to go up to 170°C. But at 168°C or so there was a big explosion. The...

[Q] Calorimeter?

... calorimeter was under the ceiling, it was quite a loud bang, so that the whole institute came down and said, 'What happened?' And also Eucken came and he started shouting at me, said, 'What did you do? My heavy water, the whole thesis is now gone'. And he said, 'The heavy water, we never get it back'. So I tried to tell him something but he didn't let me say anything. So I finally got a little bit ‒ how should I say ‒ stubborn, and next morning I tried to make order, and I was there for ten minutes and Eucken came in and said, 'What should I do with you now? The whole thesis is gone'. I said, 'Well, I build a new machine, that takes four weeks, and we can go on'. 'Oh', he said, 'don't talk this nonsense, it's not the machine... the heavy water'. And I went to the board and took out the flask with the heavy water and say, 'Here, you have your heavy water. You wouldn't believe that I did this experiment, the first experiment, with heavy water. Of course I used ordinary water to test the machine'.

And then that was a great relief, and from then on I had the complete freedom to do what I wanted to do, Eucken never interfered with my work. And I think I got pretty arrogant. I know that some day he came, he knew that the specific heat was going through a maximum at normal temperatures, near 50°C, and so that means that the heating curve was exactly linear in that range, so he asked me to plot the curve on very large graph paper and then he came with his ruler and looked. He say, 'Yes, pretty good, but 1 millimetre is missing up there'. And I said arrogantly, 'That's not my curve, that's your ruler'. And then he said, 'Let's test it in the machine shop'. And we tested it, and it was his ruler, it was not my curve.

So from then on I really had all the freedom to do my work and was much respected by him, and that means I was... I was 23 when I finished my thesis. Nowadays you can't do that any more.