Determination of hydrofluoric acid, ammonium fluoride, and maleic acid in acid cleaning solutions
AN-H-115
pt_BR
<p>A direct thermometric titration (TET) with 2 mol/L NaOH is used to determine the HF, NH<sub>4</sub>F, and maleic acid (C<sub>4</sub>H<sub>4</sub>O<sub>4</sub>) contents of acid cleaning solutions. Three endpoints (EPs) are obtained, which may be assigned as follows:</p><p><br />EP1: C<sub>4</sub>H<sub>4</sub>O<sub>4</sub> (pKa1 = 1.9), HF (pKa = 3.17)<br />EP2: C<sub>4</sub>H<sub>4</sub>O<sub>4</sub> (pKa2 = 6.07)<br />EP2: NH<sub>4</sub>F (pKa = 8.2)</p><p><br />The HF content is determined by subtracting the difference (EP2-EP1) from EP1.</p>
A direct thermometric titration (TET) with 2 mol/L NaOH is used to determine the HF, NH4F, and maleic acid (C4H4O4) contents of acid cleaning solutions. Three endpoints (EPs) are obtained, which may be assigned as follows:
EP1: C4H4O4 (pKa1 = 1.9), HF (pKa = 3.17)
EP2: C4H4O4 (pKa2 = 6.07)
EP2: NH4F (pKa = 8.2)
The HF content is determined by subtracting the difference (EP2-EP1) from EP1.