The fulvic acids form a group of organic acids with inhomogeneous composition. Like the humic acids and humins, they are produced during decomposition of plant material (humification), but in comparison to humic acids, they have a significantly lower molar mass and more acidic characteristic. Fulvic acids are much better soluble in an acidic environment than humic acids – a property that can be used to separate both groups of substances. Fulvic acids give water a brownish-yellowish color and increase its COD value (chemical oxygen demand).