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The Instability of Ascorbic Acid in Water, with Added Copper or Hydrogen Peroxide or Both¹

Division of Dairy Products Research Laboratories, Bureau of Dairy Industry, Agricultural Research Administration, U. S. Department of Agriculture, Washington 25, D. C.

ABSTRACT

Results obtained in our laboratories caused us to suspect that impurities in the water from a laboratory still were hastening the oxidation of ascorbic acid solutions. They led us to investigate the effect of different factors, particularly the source of the water, upon the stability of ascorbic acid solutions. A water solution of ascorbic acid is used in standardizing the dye, 2,6-dichlorophenol-indophenol, with which the amount of this form of vitamin C in milt and in other fluids can be determined.

Water from the laboratory still was obtained by evaporating tap water in a reservoir indirectly heated by steam, collecting the condensate in large earthenware jars, and then drawing it from a tin lined bronze faucet through 12 to 14 feet of tin lined iron pipe. However, the condensate came in contact with brass couplings which contain a high proportion of copper.

The concentration of ascorbic acid in the various water solutions and in the milk was determined by titration in acid solution (sulfuric) with 2,6-dichloro-phenolindophenol (4, 14).

¹ This work was done with funds from the Research and Marketing Act of 1946.