1. Solving a chemistry problem

4. For the luminescent determination of boron in ore, a sample of 0.2500 g was dissolved and, after appropriate treatment, the volume of the solution was increased to 100.0 ml. Then an alcoholic solution of benzoyl was added to 1.00 ml of the solution and the luminescence intensity of the resulting solution was measured. It turned out to be 0.86. Standard solutions contained 4.00; 10.0 and 20.0 mg of boron per 100 ml. After adding the same reagents and in the same quantities to 1.00 ml of each standard solution as in the case of the test solution, their luminescence intensity turned out to be 0.38; 0.65 and 1.08 respectively. Construct a calibration graph and determine the percentage of boron in the ore