humiinit
Humiinit are a class of organic compounds found in humic substances, which are major components of soil organic matter. Humic substances are complex mixtures derived from the decomposition of plant and animal matter by microorganisms. Humiinit specifically refer to the fraction of humic substances that is soluble in dilute alkali but insoluble in dilute acid. This solubility characteristic is key to their identification and separation from other humic fractions like humic acids and humins.
The precise chemical structure of humiinit is not fully understood due to their heterogeneity and complexity.