en1122公式中的F是什麼？

标准上面讲得很清楚的啊：
F:the dilution factor of the test solution and the reagent blank solution.

M:the mass, in grams of the test portion
C:the cadmium concentration in milligrams per litre of the test solution
R:the cadmium concentration in milligrams per litre of reagent blank solution