PROPERTIES OF THE YELLOW ORGANIC ACIDS OF NATURAL WATERS 1

Gel filtration profiles obtained from a variety of naturally colored waters indicate that color producing molecules are mostly in the apparent molecular weight range of 700–10,000 relative to dextrans. One fraction seems to have a molecular weight in excess of 50,000. The apparent size of the color molecules was found to be p H dependent, increasing as p H increases. Size increases are attributed to increased functional group ionization and a decrease in the adsorbability on Sephadex. The degree of association of color molecules with iron was also found to be pH dependent, being greater at both high and low p H than in the range of 7–8.