Humic substances in soils and sediments can be divided into three main fractions: humic acids, fulvic acids, and humin. 
Humic and fulvic acids are extracted from soil and other solid phase sources into a strongly basic aqueous solution of sodium hydroxide or potassium hydroxide.
*Humic acids are precipitated from this solution by adjusting the pH to 1 with hydrochloric acid.
*The alcohol-soluble portion of humic fraction is, in general, named ulmic acid.
** So-called "gray humic acids" (GHA) are soluble in low-ionic-strength alkaline media.
** "Brown humic acids" (BHA) are soluble in alkaline conditions independent of ionic strength
* Fulvic acids is left in solution at pH 1. They remain soluble independent of pH and ionic strength.
* Humin is insoluble in dilute alkali.
The International Humic Substances Society (IHSS) advocates the use of standard laboratory methods for preparation of humic and fulvic acids.  Humic substances are extracted from soil and other solid sources using NaOH, the humic acids are then precipitated at pH 1, and the soluble fraction is treated on a resin column to separate fulvic acid components from other acid soluble compounds.  Humic acid plus fulvic acid are extracted from natural waters using a resin column after microfiltration and acidification to pH 2. The humic materials are eluted from the column with NaOH and humic acid is precipitated at pH 1.  After adjusting the pH to 2 the fulvic acid is separated from other acid soluble compounds using a resin column as with solid phase sources.  An analytical method for quantifying humic acid and fulvic acid in commercial ores and products, has been developed based on the IHSS humic acid and fulvic acid preparation methods,
Extracted humic acid not a single acid; rather, it is a complex mixture of many different acids containing carboxyl and phenolate groups so that the mixture behaves functionally as a dibasic acid or, occasionally, as a tribasic acid. Commercial humic acid used to amend soil is manufactured using these same well established procedures. Humic acids can form complexes with ions that are commonly found in the environment creating humic colloids.
As a nutrition supplement, fulvic acid can be found in a liquid form as a component of mineral colloids. Fulvic acids are poly-electrolytes and are unique colloids that diffuse easily through membranes, whereas all other colloids do not.
A sequential chemical fractionation called Humeomics can be used to isolate more homogeneous humic fractions and determine their molecular structures by advanced spectroscopic and chromatographic methods. Substances identified in humic extracts and directly in soil include mono-, di-, and tri-hydroxycarboxylic acids, fatty acids, dicarboxylic acids, linear alcohols, phenolic acids, terpenoids, carbohydrates, and amino acids.