71. Solving a chemistry problem

1. To determine the content of ferric iron in concentrated sulfuric acid in the form of sulfosalicylate, a sample is placed in a flask with a capacity of 100.0 ml, the necessary reagents are added and brought to the mark with water. The optical density is measured at a wavelength of 420 nm in a cuvette with a light-absorbing layer thickness of 1 cm. The molar coefficient of light absorption under these conditions is 6000. Calculate the weight of the sample of acid for analysis if the mass fraction of iron was 0.01%, and the optimal value of the optical density is 0.435 .