A study of the “david” reaction

(1) Some of the variables influencing the David reaction have been studied. An improved method is described. (2) Among the oestrogens studied only compounds with a 17β and a 16α, or 16β-hydroxyl group gave a positive David reaction; the approximate relative chromogenicities were oestriol:100, 16-epioestriol: 60, 6-hydroxyoestriol: 16 and 2-hydroxyoestriol: 7%. (3) The presence of highly purified methylated and chromatographed urinary residues greatly diminished the David chromogenicity of oestriol. This decrease was linearly related to log concentration of urinary residue.