His first important research work, undertaken as part of his doctoral studies under E. H. Riesenfeld in the early 1920s, concerned ozone, . Schwab was the first to describe the preparation of pure ozone and its solidification, thereby accurately determining many of its physical constants. At the time, it was still not certain whether the tetratomic species oxozone, , was also present in ozone samples. The work of young Schwab conclusively refuted the century-old theory of oxozone, which led to the exceptional grade of his dissertation.