The ordinary air we breathe contains several gases which are of great value to industry and science. Oxygen, for example, is essential in making steel, and helium is required by scientists who study the behavior of materials at extremely low temperatures. However, gases normally take up so much space that they must usually be liquefied, or condensed into smaller volumes, for economical transportation and distribution.

Although scientists had produced them in the laboratory for some time, liquid gases were unavailable commercially until the late nineteenth century. Oxygen and nitrogen--the two primary gases contained in air--had been liquefied, but only small amounts of the liquid gases had been produced. German chemist Karl von Linde changed that when he invented a continuous process for producing large quantities of liquid air in 1895. British chemical engineer William Hampson (1854-1926) is also credited with making...