Patent ID: 8097169

Claim:
A method for filtering a chemical in which a first chemical stored in a first tank is filtered by a filter and a second chemical obtained by the filtering is stored in a second tank, the method comprising: inspecting the first chemical that is n-th (n is an integer equal to or larger than 1) stored in the first tank, and measuring a first measurement value, the first measurement value being a concentration of an impurity contained in the first chemical or an amount per unit volume of impurity contained in the first chemical; measuring a passage liquid measure of the first chemical, which is n-th stored in the first tank, passing through the filter; filtering the first chemical that is n-th stored in the first tank to inspect the second chemical n-th stored in the second tank, and measuring a second measurement value, the second measurement value being a concentration of an impurity contained in the second chemical or an amount per unit volume of impurity contained in the second chemical; multiplying a value, which is obtained by subtracting the second measurement value from the first measurement value, by the passage liquid measure, and measuring a capture amount of the impurity captured by the filter, in the impurity contained in the first chemical; adding the capture amounts corresponding to the individual first chemicals first to n-th stored in the first tank, and getting an added capture amount; and comparing the added capture amount and a predetermined limit capture amount of the filter, and exchanging the filter based on the comparison result.