17. Solving a chemistry problem

181. When analyzing a sample of 0.9829 g for the content of cobalt by the chemiluminescent photographic method, the glow of a sample of the analyzed solution, standards and a blank experiment was taken on one plate. 0.5 ml of a cobalt salt solution was placed into the cells of the cuvette, sodium salicylate was added (to eliminate the interfering effect of copper and iron cations) and the same amount of hydrogen peroxide. Then the cuvette was held until the glow ceased completely; the plate was photometered on an MF-2 microphotometer. The ΔS value of standard solutions containing 4.0; 8.0; 12.0; 16.0 μg Co/ml, amounted to 0.17; 0.28; 0.40 and 0.53, respectively. Calculate the mass fraction (%) of Co in the sample if ΔSx = 0.30.