The Frankfurt laboratories were quite an eye-opener to anyone coming from Glasgow or, for that matter, Oxford. Organic micro-analysis was being done as a routine service, catalytic hydrogenation using Skita-type colloidal platinum and palladium catalysts at room temperature and atmospheric pressure was normal practice, while glass apparatus with standard interchangeable ground joints was in widespread use; these, with many other gadgets like Jena sintered glass filters and so on, were unknown in the laboratory I had come from and, I suspect, in virtually all British laboratories. Borsche was a good person to work with - a good experimentalist and a patient supervisor. He had little enthusiasm for theory being a typical example of the classical German organic chemist. He was, however, completely devoid of the arrogance shown by many of his contemporaries, and indeed it has always seemed to me that it was his very gentleness and his patent desire to avoid strife that prevented him from earning a more prominent place in German science than he in fact occupied. I had some personal experience of this in my doctoral work. Among the various dehydration products of cholic acid, apocholic acid, the structure of which I sought to elucidate, was something of an anomaly. My work on it led me in due course to recognise that it was impossible to ascribe to it any structure compatible with the then accepted carbon skeleton of the sterols and bile acids. That skeleton had been proposed by Wieland and Windaus who had received the Nobel Prize for chemistry in 1928 in recognition of their massive work on bile acids and sterols respectively, and both of them were held in the greatest respect by Borsche, who had himself been an associate, and remained a tremendous admirer, of Windaus. When, towards the end of 1930, I told Borsche that, in my opinion, the Wieland — Windaus structure for the bile acids must be wrong and suggested an alternative which would accommodate my results with apocholic acid he was much disturbed. He pointed out that this would imply that there were errors of fact or of interpretation in the work of Windaus and that it would be presumptuous of me to suggest such a thing. It was only after much persuasion, aided perhaps by news that the accepted formula was suspect in Munich also, that he finally agreed to publish my work in Zeitschrift fur Physiologische Chemie (1931, 198, 173). The structure which I proposed embodied a sevenmembered ring and was, of course, erroneous, although, oddly enough, in its favour I pointed out that the skeleton could be derived from farnesol and two hexose molecules! I was probably too young and inexperienced to press on to the proper answer on my own, and Borsche felt - perhaps wisely, and certainly generously - that we should let Windaus have our results and leave any further follow-up to him. So it was that, when I completed my doctorate and returned to England, I left the sterol/bile acid field and never returned to it.
Julius von Braun, the Director of the Chemical Institute, was a very different type from Borsche. Also rather a small man, he had a rather round bullet-cropped head, atop a very short neck. He had a rather florid complexion which matched his aggressive manner; rather incongruously he had a rather high-pitched squeaky voice. He was known variously in the laboratory as 'der edle Pole' and 'der Bonze' and his assistants as well as his doctoral students (who described him as 'katzen-freundlich'), were certainly made to toe the line. He could be, and usually was, quite single-minded in his approach. In my time in Frankfurt he had a group of students working on the structure of naphthenic acids which occur in petroleum. I remember in particular one of these students called Gradstein, who seemed to spend most of his waking hours ozonising naphthenic acids down in the departmental cellar where von Braun kept a large ozone generator. One afternoon there was a substantial explosion in the cellar - loud enough to cause considerable alarm even up in my laboratory on the second floor. We promptly rushed downstairs, and pushed open the cellar door; there was a certain amount of smoke about, and the unfortunate Gradstein was lying flat on the floor apparently unconscious (it transpired later that he had merely fainted).
I and the others were about to go to his aid when von Braun arrived, pushed everyone aside, stepped over the prostrate Gradstein and said ']a, und die Substanz?' There must be many stories about von Braun. I did not have a great deal to do with him myself, nor did my colleagues Blount and Morrison. For one thing, I don't think he really approved of our working with Borsche rather than with him and, for another, I rather blotted my copybook with him quite early on before my German was fluent enough to permit of diplomatic or evasive answers. One day at the beginning of the Wintersemester 1929 he asked me if I would come along to the seminar he ran for his research students. I asked when it was held and he told me it was on Saturday at 8 a.m. I suppose I should really be ashamed of myself, but I am afraid I told him in my very blunt German that I was busy on Saturdays, and that in any case 8 a.m. was far too early for me. Perhaps it is not surprising that our relations thereafter were rather cool. Nevertheless, whatever his faults, von Braun was a brilliant reaction chemist and I learned quite a lot from him during my stay in Frankfurt. With von Braun and Borsche on the organic side, Schwarz in inorganic, Dieterle in pharmaceutical, and, across the road, Bonhoeffer in physical chemistry we had a strong and on the whole harmonious chemical school. It is sad to think that all of them fell foul of, and suffered under, the Nazi regime in later years - not, as far as I know, because of Jewish ancestry, but because they had independent minds.