'Iodine number' is the grams of iodine atoms (atomic mass =127 ~g ~mol ⁻¹ ) that can react completely with100 g of a vegetable oil. Iodine monochloride (ICl) is a reagent used to determine iodine number. In an experiment, 25.00 ~cm ^3 of 0.100 ~mol dm ⁻³ ICl was added to 127 g of the oil. The unreacted ICl was found to be equivalent to 40.00 ~cm ^3 of 0.10 ~mol dm ⁻³ of Na ₂ ~S ₂ O ₃ . The iodine number of the oil ca