26(3). To construct a calibration graph, 5.00 8.00 10.00 ml of ferric ammonium alum solution with T(Fe) = 0.0000500 was placed in flasks with a capacity of 50.00 ml, hydrochloric acid was added to potassium thiocyanate, brought to the mark with water and the optical density was measured at 495 nm:
U, ml 5.00 8.00 10.00
A, 0.365 0.595 0.750
The test solution containing iron and nickel was diluted in a 100.00 ml flask, and two 20.00 ml aliquots were taken into 50.00 ml flasks. One sample was diluted to the mark with water. The optical density of the first sample at 495 nm is equal to A Ni=0.060. The optical densities of the second sample for different options are equal
Option 3
0.660

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