Neutral Silver Nitrate as a Reagent in the Chromatographic Characterization of Pheholic Compounds SIR: I n connection with other work in this laboratory, it was necessary t o investigate the chromatographic behavior of a number of phenolic compounds which are often associated with natural plant products. Five solvents (Table I) of the more than 100 systems investigated were superior for the separation and characterization of these compounds on paper. Table I summarizes the R, values found for 37 of these phenols and phenolic ethers. Ammoniacal silver nitrate has been in common use as a reagent for phenols ( 2 , s ) . Silver nitrate in acetone followed by sodium hydroxide has been applied to various compounds, including phenols (4). I n this laboratory, the use of
neutral silver nitrate in aqueous acetone alone has given characteristic color reactions with various phenols and certain of their ether derivatives (Table I). The development time is also a characteristic of the compound involved. -4s the color reaction develops ivith a background color, the spots are marked with pencil and finally all color can be removed with t h e application of 2070 nitric acid. The paper is not injured by such treatment, if it is washed thoroughly with water. Thus, a record suitable for filing is obtained. All chromatograms were prepared by the ascending method a t 26.7' i 1 C. in a solvent-saturated atmosphere. The
compounds (20 y from ethanol solution) were placed 2 inches from the bottom of Whatman No. 1 paper, which was then stapled along the sides to form a cylindrical shape. The solvent front was allowed t o run approximately 14 inches in cylindrical borosilicate glass tanks (5 inches in diameter X 18 inches) containing 100 ml. of solvent. The tanks were sealed at the top with a saran film held in place with a rubber band. Reagent grade acetic acid and ethanol and distilled water were used. The other solvents were technical grade. All solvent ratios refer to volume. The acetone-silver nitrate reagent was prepared by adding 50 ml. of saturated aqueous silver nitrate to 1 liter of acetone and then adding just enough water t o dissolve the precipitate. Chromato-
Table I.
Benzoic acida 3-(OH) 4-(OH) 2,4-(OH)2 3,4-(OH)' 2,3,4-(OH)a 3,4,5-(0H)s 4-(OH)-3-(OCH
