50. To prepare standard solutions of titanium (IV) and vanadium (V), a weighed portion of steel that does not contain vanadium and titanium was dissolved in nitric acid. In six volumetric flasks
with a capacity of 50.0 ml, identical aliquots of the resulting solution were placed, 0.50 was added; 1.00; 1.50 ml of a solution containing 0.20 mg / ml titanium (IV) or vanadium (V), hydrogen peroxide, and brought up to the mark with water. We measured the optical densities of titanium (IV) peroxide complexes at 400 nm and vanadium (V) at 400 and 619 nm relative to a reference solution containing all components except H2O2. Received the following data to build a calibration graph - table 8

Parameter Vanadium (V) Titanium (IV)
V, ml 0.5 1.0 1.5 0.5 1.0 1.5
A400 0.16 0.34 0.51 0.29 0.57 0.86
A619 0.06 0.12 0.18 0.0 0.0 0.0
From a sample of steel with a mass of m (g), after appropriate processing, 100.0 ml of a solution was prepared. An aliquot of 10.0 ml was taken into a flask with a capacity of 50.0 ml, solutions of H2O2, HNO3 were added and made up to the mark with water. The optical density was measured at 400 and 619 nm relative to an aliquot of the test mixture that did not contain H2O2. Calculate the mass fraction (%) of vanadium and titanium in steel (in accordance with the number
tasks) according to table 9.
m, g 0.25
A400 0.94
A619 0.11

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