The main regularities of the two-stage variation in characteristics of low-concentration aqueous lucigenin solutions are discussed on the basis of studying their optical properties (luminescence). At the first stage, the lucigenin concentration decreases with decreasing fixed state of the solution, and at the second stage, after lucigenin is exhausted, regular oscillations about the constant level are observed. The problem of determining dilution multiplicities (as geometric ratios) and initial concentrations of the diluted substance is analyzed.