50. Solving a chemistry problem

2. A hitch of phosphorus fertilizer weighing 0.3000 g was dissolved and transferred to a measured flask with a capacity of 250 ml. 10 ml of the resulting solution was placed in a measured flask for 50 ml, added a reagent for phosphorus and brought to a label with distilled water. The optical density of the resulting solution was Ax = 0.18. For standard solutions containing 1, 2, 3 and 4 mg of phosphorus in 50 ml, in the same conditions, optical 92 density was 0.08, respectively; 0.15; 0.24 and 0.33. Build a calibration schedule and determine the mass fraction (%) of phosphorus in fertilizer.