Hampson’s air liquefier

The other day I wandered down to our department’s stores to be met by the deafening roar of a liquid nitrogen tanker filling a queue of patient steel Dewars on wheels. This weekly ritual is an echo of events that helped cement the department’s fame, and of a series of ding-dongs regarding priority for the invention of the commercial air liquefier.

Although philosophers like Giambattista Della Porta introduced freezing mixtures in the late Renaissance, chemistry remained a subject dominated by flames and furnaces until the start of the 19th century. The only way to reach low temperatures was to start from ice either harvested in winter and stored in ice houses, or imported by ship from Canada or Norway. Then in the late 1840s an American doctor, John Gorrie, developed the first ice maker based on the rapid expansion of compressed air. In a patent filing of 1857, the engineer Charles Siemens suggested an improvement. What if the cold air issuing from the device was used to pre-cool the incoming air? Although he did not complete his patent, the idea of ‘regenerative’ cooling would spread across the burgeoning refrigerator industry.