Abstract: Taking advantage of their difference, the quantity of the non-active component, para B, in the acidified timgstate solution aged by heating can be determined. Making use of the method of H₂O₂-SO₂, the rate of formation of para Bare determined at 80℃ with Zvalues (H⁺/W) equal to 0.667,0.850,1.00 and 1.14 respectively. It is found that expect the solution with Z=1.14 in which the disproportionation reaction may occured, in all the solutions with other Zvalues the formations of,para Eare very slow. The characters of the changing of the rates of para Bformation are linear, and the formation rate decreases as the Zvalue increases. The activity difference with H₂O₂between para A and B is explained according to their structure.