125. Solving a chemistry problem

2. To determine folic acid, the polarography method was used. In volumetric flasks with a capacity of 50 ml, reference solutions were prepared with various precisely known concentrations c (FA) of folic acid, polarograms of these solutions were taken, and for each solution, the height h of the polarographic wave corresponding to the diffusion current of folic acid was measured:
C(FA), mg/ml 0.15 0.25 0.35 0.45
h, mm 56 94 134 172
An aliquot of the analyzed solution with a volume of Va = 8.0 ml was taken into a volumetric flask with a capacity of 50 ml, the corresponding background electrolyte was added, diluted with water to the mark, and the test solutions were obtained. Under the same conditions in which the polarography of the reference solutions was carried out, a polarogram of the test solution was taken and the height h of the wave was measured - 122 mm. Build a calibration graph in the coordinates h, mm - C (FC), mg / ml and, using the data below, determine the concentration (mg / ml) of folic acid in the analyzed solution.
Draw a diagram of a polarogram and show how the wave height is found graphically. Name and indicate in the figure the parameter by which the substance is identified by the polarographic method.