Abstract
Ethyl comenate, obtained in a simple manner from the residue left after extraction of morphine from opium, showed stable color reaction with Fe3+ and this coloration was followed by spectrophotometry, from which the use of ethyl comenate as analytical reagent for Fe3+ was examined. The fact that this coloration is due to chelate formation was confirmed by potentiometric titration using a glass electrode pH meter. It was found through the Job method that the composition of the chelate in dil. sulfuric acid solution is Fe3+/R=1/2, while that in Walpole's buffer of pH 5.0 is 1/3. Dissociation constant in this buffer was 5.3×10-12 by the molar ratio method and excess of the reagent prevented dissociation. The colored solution was no change in its absorbancy at 420mμ for 4-68 hours after coloration, indicating this color to be stable.
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