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HUMIC ACID

HUMIC ACID

CAS NO:  1415-93-6
EC/LIST : 638-738-6

Humic acid are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). 
For a long era in the 19th and 20th centuries, humic substances were often viewed through a lens of acid–base theory that described humic acids, as organic acids, and their conjugate bases, humates, as important components of organic matter. 
Through this viewpoint humic acids were defined as organic substances extracted from soil that coagulate (form small solid pieces) when a strong-base extract is acidified, whereas fulvic acids are organic acids that remain soluble (stay dissolved) when a strong-base extract is acidified.

Humic acid in isolation is the result of a chemical extraction from the soil organic matter or the dissolved organic matter and represent the humic molecules distributed in the soil or water.
A new understanding views humic substances not as high-molecular-weight macropolymers but as heterogeneous and relatively small molecular components of the soil organic matter auto-assembled in supramolecular associations and composed of a variety of compounds of biological origin and synthesized by abiotic and biotic reactions in soil.
Humic acid is the large molecular complexity of the soil humeome that confers to humic matter its bioactivity in soil and its role as plant growth promoter

Humic acid a simple question with a complex answer. 
Here's a breakdown of what exactly humic acid is, how it forms, why the source of humics is vitally important, and how you can be sure you're getting a superior product.

Humic acids are fully decomposed remains of organic life. 
They're long-chain molecules that are high in weight and dark brown in color. 
They are not a single acid. 
Rather, "humic acid" is a broad term that refers to a complex mixture of many different acids that are soluble in alkaline solutions. 
They exist naturally as part of nature's life cycle in soils, oceans, and streams.

humic acid, one of two classes of natural acidic organic polymer that can be extracted from humus found in soil, sediment, or aquatic environments. 
The process by which humic acid forms in humus is not well understood, but the consensus is that it accumulates gradually as a residue from the metabolism of microorganisms. 
Humic acid structure is unlike that of proteins or carbohydrates, the two most common organic polymers found in biological material; instead, humic acid can be characterized as a loose assembly of aromatic polymers of varying acidity and reactivity.

Humic acid has the average chemical formula C187H186O89N9S1 and is insoluble in strong acid (pH = 1). 
A 1:1 hydrogen-to-carbon ratio indicates a significant degree of aromatic character (i.e., the presence of benzene rings in the structure), whereas a low oxygen-to-carbon ratio indicates fewer acidic functional groups than occur in fulvic acid, the other acidic organic polymer that can be extracted from humus. 
Transition and heavy metals—for example, Fe3+ or Pb2+—as well as other compounds having aromatic or hydrophobic (water-insoluble) chemical structures (i.e., organic pesticides or anthropogenic hydrocarbons), react strongly with humic acid. 
This property makes it an effective agent in sequestering many of the pollutants in terrestrial and aquatic environments.

Humic and Fulvic acids are the final break-down constituents of the natural decay of plant and animal materials. 
These organic acids are found in pre-historic deposits. 
Humic matter is formed through the chemical and biological humification of plant and animal matter and through the biological activities of micro-organisms. 
Humic acids are complex molecules that exist naturally in soils, peats, oceans and fresh waters. 
The one source of humic acids are the sedimentation layers referred to as Leonardite.
These layers were originally deep in the earth’s crust, but over many years have been exhumed to near-surface location. 
Humic acids are found in high concentration in these layers. 
Leonardite is organic matter, which has not reached the state of coal and differs from soft brown coal by its high oxidation degree, a result of the process of coal formation, and has no value as fuel. 
The decomposition of concentrated organic acids is a lengthy process taking millions of years in the natural environment.
Imagine, if you will, a prehistoric marsh or peat bog. 
Plants are harvesting carbon dioxide from the atmosphere and using the sun’s energy to build plant biomass. 
These plants feed insects and vertebrates. 
As plants and animals die they contribute their carbon back to the bottom of the bog.
Over millions of years this cycle of organic matter is concentrated and compressed into layers in the earth. 

Humic acid is derived from leonardite shale and is among the most concentrated organic material available. 
Elemental analysis of humic acid has shown it to consist largely of carbon and oxygen (about 50% and 40% respectively). 
Humic acid also contains hydrogen (about 5%), nitrogen (about 3%), phosphorous and sulfur (both less than 1%). 
Humic acid is a complex of closely related macromolecules. 
These molecules range in size from less than 1000 to more than 100,000 daltons, with the lower mass representing the younger material.

The exact composition of humic acid varies from one source to another. 
Our humic acid comes from North Dakota and is derived entirely from trees and vegetation, which were laid down in the carboniferous period when that area was the tropical sun belt of North America. 
Over the ages, the vegetation underwent compaction and heating. 
Humic acid slowly carbonized and became coal. 
This compaction squeezed out the organic acids and esters present in the vegetation, forming a pool on top of the coal bed. 
This pool dried, aged, and eventually became leonardite shale. 
Because of its vegetative origin, this material is very rich and beneficial to plants today.


Humic acid is an organic substance in the soil and is important for soil fertility, as well as for flora. 
Strong organic compounds are broken down by micro-organisms and converted into humus; this is what we call humification. 
Because humus is a collection of different organic substances, the term humic substances is also used.

Humic acids are amphiphilic species whose behavior in aqueous solution suggests that they form pseudomicelles–aggregates akin to the micelles familiar from synthetic surfactant chemistry. 
Humic acid is thought that humic pseudomicelles can be formed by both intramolecular coiling and intermolecular association, depending on the molecular weight, structural characteristics, and polydispersity of the humic acid in question. 
The process does not feature a critical micelle concentration. 
Experimental evidence indicates that metal ions enhance the detergent character of dissolved humic acid by facilitating the coiling and folding of the polymer chains. 
A recently conceived alternative model suggests that humic acids consist of relatively small subunits that associate through weak molecular interactions. 
This view appears to run counter to certain experimental observations, but deserves careful attention. 
The strong association between metal ions and solid humic acid makes it possible to use an inexpensive commercial grade for the decontamination of polluted water. 
A continuous elution process through a column packed with humic acid allows for the removal of both heavy metals and organic xenobiotics from aqueous solution.

Humic acid is a natural, acidic, organic polymer commonly used for pollutant removal. 
Available in various chemical compositions and molecular structures, humic acid can be described as a loose assembly of aromatic polymers of varying acidity and reactivity.

Extensive evidence supports the fact that soil organic matter is a critical component of soil productivity and sustainable fertility by interaction with other soil components through a series of complex biochemical interactions controlled by living organisms. 
Humic substances, categorized as humic acid, fulvic acid and ulmic acids (humin) are important components of soil organic matter that are involved in nearly all biological and chemical interactions that occur in soils. 
Collectively referred to as Humic Acid, these substances increase the bioavailability of nutrients released from soil minerals through complex interactions among microbes, metals, organic matter and clays. 
Other soil organic matter constituents such as proteins, amino acids, carbohydrates, nucleic acids, lipids and lignin breakdown relatively quickly in soils. 
Humic Acids, produced from the biodegradation and chemical recombination of organic matter, are highly persistent in soil lasting for thousands or even millions of years once formed.


The formation of humic substances in nature is one of the least understood aspects of humus chemistry and one of the most intriguing. 
There are three main theories to explain it: the lignin theory of Waksman (1932), the polyphenol theory, and the sugar-amine condensation theory of Maillard (1911).
Those theories are insufficient to account for observations in soil research.
Humic substances are formed by the microbial degradation of dead plant matter, such as lignin and charcoal.
Humic substances in the lab are very resistant to further biodegradation. 
The precise properties and structure of a given sample depend on the water or soil source and the specific conditions of extraction. 
Nevertheless, the average properties of lab produced humic substances from different sources are remarkably similar.

Humic substances in soils and sediments can be divided into three main fractions: humic acids, fulvic acids, and humin.
Their presence and relative abundance is inferred by lab extraction, a process which alters their original form beyond recognition. 
The humic and fulvic acids are extracted as a colloidal sol 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, leaving the fulvic acids in solution. 
This is the operational distinction between humic and fulvic acids. Humin is insoluble in dilute alkali. 
The alcohol-soluble portion of the 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; and fulvic acids (FA) are soluble independent of pH and ionic strength. 

Humus in nature is produced by biodegradation of tissues from dead organisms and is thus roughly synonymous with organic matter; distinctions between the two are often not precisely and consistently made.

Humic acid as traditionally produced in a laboratory is 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. 
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. 
Humic acids are insoluble in water at acid pH, whereas fulvic acids are also derived from humic substances but are soluble in water across the full range of pH.
Humic and fulvic acids are commonly used as a soil supplement in agriculture, and less commonly as a human nutritional supplement.
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-hydroxy acids, fatty acids, dicarboxylic acids, linear alcohols, phenolic acids, terpenoids, carbohydrates and aminoacids

Decomposition products of dead plant materials form intimate associations with minerals, making it difficult to isolate and characterize soil organic constituents. 
18th century soil chemists successfully used alkaline extraction to isolate a portion of the organic constituents in soil. 
This led to the theory that a 'humification' process created 'humic substances'; most commonly 'humic acid', 'fulvic acid', and 'humin'.
However, these humic substances have not been observed in soil. 
Although 'humification' theory is unsupported by evidence, "the underlying theory persists in the contemporary literature, including current textbooks."
Attempts to redefine 'humic substances' in valid terms have resulted in a proliferation of incompatible definitions, "with far-reaching implications beyond our ability to communicate scientifically accurate soil processes and properties


Since the dawn of modern chemistry, humic substances are among the most studied among the natural materials. 
Despite long study, their molecular structure and chemical remains elusive. 
The traditional view is that humic substances are heteropolycondensates, in varying associations with clay.
A more recent view is that relatively small molecules also play a role.
Humic substances account for 50 – 90% of cation exchange capacity. 
Similar to clay, char and colloidal humus hold cation nutrients.

A typical humic substance is a mixture of many molecules, some of which are based on a motif of aromatic nuclei with phenolic and carboxylic substituents, linked together; the illustration shows a typical structure. 
The functional groups that contribute most to surface charge and reactivity of humic substances are phenolic and carboxylic groups.
Humic acids behave as mixtures of dibasic acids, with a pK1 value around 4 for protonation of carboxyl groups and around 8 for protonation of phenolate groups. 
There is considerable overall similarity among individual humic acids.
For this reason, measured pK values for a given sample are average values relating to the constituent species. 
The other important characteristic is charge density. 
The molecules may form a supramolecular structure held together by non-covalent forces, such as van der Waals force, π-π, and CH-π bonds. 

The presence of carboxylate and phenolate groups gives the humic acids the ability to form complexes with ions such as Mg2+, Ca2+, Fe2+, and Fe3+. 
Many humic acids have two or more of these groups arranged so as to enable the formation of chelate complexes.
The formation of (chelate) complexes is an important aspect of the biological role of humic acids in regulating bioavailability of metal ions


Humic acids chelate nutrient compounds, especially iron, in the soil to a form suitable for plant utilization. 
Thus, the nutrient supply of plants is optimized. 
Increases up to 70% in yield, accompanied by a reduction up to 30% in the use of fertilizers and pesticides, as well as better and healthier growth
of green grass, ornamentals, agricultural crops and woods can be attained with the regular application of first-quality humic acids. 
Furthermore, water holding capacity of soils is increased considerable, which means that the use of water can be reduced substantially.
Best economic results can be obtained in light and sandy soils poor in humus, as well as on recultivation fields. 
The diverse positive impacts of humic acids are to be observed particularly in such soils. 
This is true for almost all soils in dry and warm regions. 
As a result of the high mineralization rate of organic substances, providing these soils with stable humic acids is indispensable for the maintenance and improvement of soil fertility.
Current scientific studies show that the fertility of soil is determined to a very large extent by the content of humic acids. 
Their high cation-exchange capacity (CEC), the oxygen content as well as the above average water holding capacity are the reasons for the high value of using humic acids for improving soil fertility and plant growth. 
The most important feature of humic acids lies in their ability to bind insoluble metal ions, oxides and hydroxides, and to release them slowly and continually to plants when required. Due to these properties, humic acids are known to produce three types of effects: physical, chemical and biological


Leonardite is not a fertilizer. 
Humic acid acts as a conditioner for the soil and as a bio-catalyst and bio-stimulant for the plant. 
Humic acids are an excellent natural and organic way to provide plants and soil with a concentrated dose of essential nutrients, vitamins and trace elements. 
Compared to other organic products, Leonardite enhances plant growth (biomass production) and fertility of the soil. 
Another advantage of Leonardite is its long-term effectiveness, as it does not get consumed as quickly as animal manure, compost or peat. 
Leonardite decomposes completely, therefore it does not enter into nutritional competition with plants for nutrients like nitrogen. 
This is not the case with partially decomposed compost, whereby the organic substances in soil are rapidly consumed by microorganisms and mineralized entirely without humus formation

Humic acid increases nutrient uptake, drought tolerance, and seed germination. 
Humic acid increases the microbial activity in the soil, making it an excellent root stimulator. 
Humic acid increases the availability of nutrients in our fertilizers and in those already existing in your soil. 
Humic acid will help to aerate the soil from the inside. 
Humic acid will also help to lower the pH of the soil to a more neutral level and will flush high levels of salts out of the root zone, all of which will help to promote better plant health and growth

Humic acids chemically change the fixation properties of the soil.  
Humic acid neutralizes acidic and alkaline soils; regulates pH-value of soils, increasing their buffering abilities; and has extremely high cation-exchange properties

IUPAC NAME :

Humic Acid

SYNONYMS:

231-704-8  
7693-26-7  
Hydridokalium   
Hydridopotassium   
Hydridopotassium    
MFCD00011357  
Potassium hydride   
11135-81-2  
1415-93-6  
 

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