118. Solving a chemistry problem

74. Indicate the features of the method of differential photometry.
For the photometric determination of molybdenum in a mineral with dithiol
a standard solution of ammonium molybdate was prepared by dissolving 0.100 g of it in 500 ml.
An aliquot of the solution (V, ml) after treatment with the reagent was brought to a volume of 50 ml,
photometrically. Measurement data are shown in the table:
V, ml 0.5 1.0 1.5 2.0
D 0.231 0.465 0.690 0.940
Determine the content of MoO3 in the mineral, if a sample of 0.2400 g is taken for analysis,
dissolved in 100 ml. The same reagent was added to an aliquot of it (10 ml), the volume was adjusted to 50 ml, D=0.510.