138. Задачка по химии №013 893

A weighed portion of a natural product weighing 0.780 g was dissolved in 100 cm3 and 0.05 cm3 of the solution was applied to paper. After chromatographic separation, the resulting spot of uridylic acid was cut out, fused with KOH and K2S2O8, after dissolving the melt, phosphorus was determined photometrically, obtaining the optical density of Auridil = 0.450. A solution containing 20 μg / cm3 of phosphorus was prepared from a standard phosphate solution and its optical density ATP = 0.850 was measured. Determine the mass fraction of uridylic acid (%). (M (C8N2PH13O8) = 296) in a natural product.