112. Solving a chemistry problem

61b. Furacilin has its own light absorption in the visible region of the spectrum. For the photometric determination of furatsilin considered below using the FEK-56 photoelectrocolorimeter, select a light filter (indicate its number) according to the following data:
Filter number 2 3 4 5 6 7
Maximum filtrate transmission, nm 364 400 440 490 540 590
Optical density of furacilin solution 0.21 0.31 0.71 0.38 0.30 0.23
Using the data below, using the method of one standard, calculate the content (mg) of furacilin in C ml of the analyzed solution, if, when measured under the same conditions with the selected filter, the optical density of the analyzed solution of furacilin turned out to be A (X), and the optical density of the standard solution c concentration of Cst furatsilina - Ast.
What condition is mandatory for the photometric determination of a substance in the studied concentration range using the single standard method?
Option b
V, ml100
A(X) 0.42
Cst mg/ml 0.016
Ast 0.45