Fenske’s helices

 A few years ago, an enthusiastic A-level student told me that they were going to study chemical engineering. After all, he argued to me, it was simply chemistry but on a larger, more industrially relevant scale. I reminded him of that flippant remark ‘chemistry is simply physics scaled up’; you need physics to understand it, but chemistry involves a different way of thinking. Chemical engineering, in turn, requires another step in thinking, a change which happened early in the 20th century.