The differences in the gas chromatographic retention indices of the chlorination products of aliphatic ketones and parent carbonyl compounds (ΔRI) are constant, and their numeric values depend on the number and position of chlorine atoms in the molecule. A simplest version of an additive scheme for the evaluation of retention indexes is developed to identify the chloro derivatives of carbonyl compounds. The order of the chromatographic elution of diastereomeric α,α′-dichloro-k-alkanones (k > 2) is found.