Why Are Humic Substances Called Acids?

By Richard Lamar, PhD
Senior Director of Humic Research
Bio Huma Netics, Inc.

We are accustomed to seeing humic substances (humic and fulvic) in dry/granular form, and we tend to think of acids as liquids. So why are humic and fulvic substances called acids?

All substances, solid AND liquid, have a chemical makeup. An acid is a chemical that can donate a proton (H+) to a water molecule (H2O, which would form H3O+) or to another chemical such as ammonia (NH3, which would form NH4+).

Organic acids are generally weak acids that do not completely dissociate (i.e., donate a proton) in water in the way that strong mineral acids do, such as in the case of hydrochloric acid (HCl). The most common organic acids are carboxylic acids, sulfonic acids, phenols and alcohols (Figure 1).

Organic acids can be aliphatic (structured as open chains rather than aromatic rings), such as acetic acid (Fig. 1A) or ethanol (Fig. 1E). Organic acids can also be aromatic (made up of ring structures, originally named so because of their fragrant properties), such as benzoic acid (Fig. 1B), benzene sulfonic acid (Fig. 1C) or phenol (Fig. 1D).

All of these structures can be found in humic and fulvic acids, sometimes all in the same molecule. For example, one humic acid or fulvic acid molecule might contain a benzoic acid, a phenol, an alcohol, and an aliphatic carboxylic acid (Figure 2). All of these functional groups can ionize (i.e., lose their H+ atoms and contribute to acidity) (Figure 3). The primary factor affecting ionization of organic acids is pH.

Figures 1–3. Chemical structures found in organic acids

We will discuss the interrelationship of soil, pH, and humic substances in Humic Corner #4.

Video: Earth Day, 2022

Over 50 years ago, on April 22, 1970, 20 million Americans took to the streets to protest environmental destruction and to celebrate the wonders of Planet Earth. The basic message was that we had to find new ways to live our lives, raise our food, and conduct our businesses that were environmentally friendly and sustainable—that would not waste resources or pollute the air, the water, or the soil.

In the early 1970s, Bio Huma Netics and Mesa Verde Humates were independently formed to provide earth-friendly agricultural products and soil and wastewater bioremediation products.

[Read more…]

What Differentiates Humic and Fulvic Acids?

By Richard Lamar, PhD
Director of Humic Research
Bio Huma Netics, Inc.

For centuries, humic acids (HA) were thought to be composed of much larger molecules than those found in fulvic acids (FA). However, the application of Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), which separates molecules on the basis of molecular weight, demonstrates that the molecular weights of the two fractions both fall in the range of 200–800 Daltons (Da), with most of the molecules having molecular weights in the range of 200–400 Da (Figure 1). To give context, carbon (C) weighs 12 Da, oxygen (O) weighs 16 Da, and hydrogen (H) weighs 1 Da. Thus, phenol molecules (an aromatic organic compound, also called carbolic acid), which have 6 C, 1 O, and 11 H atoms, weigh 99 Da. [Read more…]

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