26. Solving a chemistry problem

61a. Furacilin has its own light absorption in the visible region of the spectrum. For the photometric determination of furatsilin discussed 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 furatsilin solution 0.21 0.31 0.71 0.38 0.30 0.23
Based on the data below, using the method of one standard, calculate the content (mg) of furatsilin in Cml of the analyzed solution, if, when measured under the same conditions with the selected light filter, the optical density of the analyzed furatsilin solution turned out to be equal to A(X), and the optical density of the standard solution with concentration of Cst furacilin - Ast.
What condition is mandatory for the photometric determination of a substance in the studied concentration range using the method of one standard?
Option a
V, ml 50
A(X) 0.32
Cst mg/ml 0.012
Ast 0.34