Abstract
1. When vitamin D2 in ethylene dichloride was allowed to stand with acetyl chloride (2 per cent of total volume) for 30 minutes at room temperature, it was easily isomerized to isotachysterol.
2. When antimony trichloride reagent without acetyl chloride was added to the isotachysterol, no color was produced. Therefore, it may be concluded that the isomerization of vitamin D to isotachysterol has no relation with the colorimetric reaction of vitamin D with antimony trichloride reagent containing acetyl chloride.
