Studies of the distribution equilibrium of Zn2 on extracted humic acid from the soil of Gorgan's Naharkhoran at different pH and determination of equilibrium constant (Kex) using flam atomic absorption

Presence of weak acidic functional groups such as carboxyl benzoic and phenolic in humic acid, enable it to act as a action exchanger between soil and plant is being supplied. However the exchange process is slow and depends on the pH of the medium. Also presence of nitrogen in the structure of Humic acid cause it to be a source of nitrogen in the soil which helps plant growth Thus the soil containing more humic acid can fertilizes better. We have selected zinc ion because it has important rol in the physiological system. In this studies discontinue or in pot ion exchange technique has been used. The amount of exchanged zinc ion with respect to dried matter atplI=7 is 1.248 mol/kg. This amount have been measured by flam atomic absorption and the calculated equivalent constant for ail initial concentration, 4. 10-3mol/lit is 0.04. Also the result obtained shows that each [Zn2] ion exchanges a single [H] ion only relative error % = 0.714 and cv% = 1.25