<p>Amount of oxalic acid present in a solution can be determined by its titration with&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>K</mi><mi>M</mi><mi>n</mi><msub><mi>O</mi><mn>4</mn></msub></math>&nbsp;solution in the presence of&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>H</mi><mn>2</mn></msub><mi>S</mi><msub><mi>O</mi><mn>4</mn></msub></math>. The titration gives unsatisfactory result when carried out in the presence of HCI, because HCI:</p>