Irving A. Breger
A. M. Pommer
1960
<p><span>The “acid nature” of humic acid has been controversial for many years. Some investigators claim that humic acid is a true weak acid, while others feel that its behaviour during potentiometric titration can be accounted for by colloidal adsorption of hydrogen ions. The acid character of humic acid has been reinvestigated using newly-derived relationships for the titration of weak acids with strong base. Re-interpreting the potentiometric titration data published by </span><span class="small-caps">Thiele</span><span> and </span><span class="small-caps">Kettner</span><span> in 1953, it was found that Merck humic acid behaves as a weak polyelectrolytic acid having an equivalent weight of 150, a </span><i>pK</i><sub><i>a</i></sub><span> of 6.8 to 7.0, and a titration exponent of about 4.8. Interdretation of similar data pertaining to the titration of phenol-formaldehyde and pyrogallol-formaldehyde resins, considered to be analogs for humic acid by </span><span class="small-caps">Thiele</span><span> and </span><span class="small-caps">Kettner</span><span>, leads to the conclusion that it is not possible to differentiate between adsorption and acid-base reaction for these substances.</span></p>
application/pdf
10.1016/0016-7037(60)90136-8
en
Elsevier
Potentiometric titration and equivalent weight of humic acid
article