text: The Acree-Rosenheim reaction is a chemical test used for detecting the presence of tryptophan in proteins. A protein mixture is mixed with formaldehyde. Concentrated sulfuric acid is added to form two layers. A purple ring appears between the two layers if the test is positive for tryptophan.
  The test was named after two greats in biochemistry, namely, Solomon Farley Acree (1875&ndash;1957), a distinguished American Biochemist at Johns Hopkins University, and Sigmund Otto Rosenheim (1871&ndash;1955), an Anglo-German Medical Chemist at the University of Manchester.