55 A portion of ore a was dissolved. Rhenium was extracted from the solution with toluene in the presence of methyl violet. The extracts were collected in a 50 ml flask, the volume was brought to the mark, and the optical density Dx was determined. The optical density of four standard solutions containing 1.0; 6.0; 8.0 and 10.0 mg/l of rhenium and subjected to similar treatment, was 0.10; 0.50; 0.64; 0.81. Build a calibration graph in the coordinates CRe - D. Determine the percentage of rhenium in the ore according to the following data:
Options A B C D
a, d 1.0000 0.5000 0.7000 1.2300
Dx 0.54 0.25 0.87 0.70

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