Humic acid
Humic acids are the result of a severe chemical extraction from the soil organic matter, and recently their natural existence was jeopardized, since it is a product of the chemical procedure. By definition, humic acids are the organic substances extracted from soil that coagulate when the strong-base extract is acidified while fulvic acids are the organic substances that remain soluble when the strong-base extract is acidified. Historically, humic acids and their conjugate bases, humates, are defined as a group of organic acids and a principal component of humic substances constituting humus, the major organic fraction of soil, peat and coal, and also a constituent of many upland streams, dystrophic lakes, and ocean water. New definitions rather refer the components of the soil organic matter as “humic substances” (not acids) or in a continuum of organic compounds in a supramolecular frame and suggest that the term “humic acids” should be avoided.
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