This paper presents the analytical technique utilized in this series of experiments. Experiments were carried out on n-hexane solution containing vitamin D₂ (I) and/or its isomers involving isocalciferol (II), 5, 6-cis-isocalciferol (III), isotachysterol (IV), precalciferol (V), 5, 6-trans-calciferol (VI) and tachysterol (VII). A mixture containing 0.1 mg of each component was chromatographed on a column (1×10 cm) of weakened alumina containing 5% water. The chromatogram was developed with 16.5% ether in n-hexane. The eluate fractions of each component were : II and VI (25-45 ml), IV and V (50-70 ml), I, III and VII (75-95 ml). Components, separated quantitatively from the mixtrue, were determined by ultraviolet spectrophotometry in isopropanol. Fractions containing nonseparable components were analyzed by means of SbCl₃ coloration after the mixtures were treated with maleic anhydride (MA). It was found that I, V, VI, and VII formed an adduct with MA in benzene within two hours at 80°, while II, III and IV give a negative reaction with MA, and that the adducts are uncolored with SbCl₃ reagent. The use of the difference in reaction rates with MA, therefore, made it possible to determine each component in the above fractions within a 10% error.