Sodium thiosulfate reacts with excess dilute hydrochloric acid according to the following equation. Na₂S₂O₃(aq) + 2HCl(aq) → 2NaCl(aq) + S(s) + SO₂(g) + H₂O(l) The reaction produces sulfur dioxide which is corrosive and toxic by inhalation. The effect of temperature on the rate of this reaction can be investigated by the 'disappearing cross experiment' as follows. step 1 Measure 10.00 cm³ of 0.100 mol dm⁻³ Na₂S₂O₃(aq) and transfer into a boiling tube. step 2 Into a second boiling tube, transfer 10 cm³ of 0.500 mol dm⁻³ HCl(aq). step 3 Heat both tubes in the same water-bath. step 4 Place a conical flask on a piece of paper, on which is drawn a large X. step 5 When the solutions reach the required temperature, remove them from the water-bath, pour the contents of both tubes into the conical flask and immediately start a timer. step 6 The X on the paper should be viewed from above the flask as shown in the diagram. step 7 When the X can no longer be seen, due to formation of solid sulfur, stop the timer. step 8 Repeat the experiment using the same volumes and concentrations of solution at different temperatures. [Figure X.X]