In 1917, he published a paper on the chemistry of oil films that later became the basis for the award of the 1932 Nobel Prize in chemistry. Langmuir theorized that oils consisting of an aliphatic chain with a hydrophilic end group (perhaps an alcohol or acid) were oriented as a film one molecule thick upon the surface of water, with the hydrophilic group down in the water and the hydrophobic chains clumped together on the surface. The thickness of the film could be easily determined from the known volume and area of the oil, which allowed investigation of the molecular configuration before spectroscopic techniques were available.