<p>An inorganic compound liberates&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>O</mi><mn>2</mn></msub></math>&nbsp;when heated, turns an acid solution of Kl brown and reduces acidified&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>. The substance is:</p>