def iodineIndex (Na2S2O3_molarity, Na2S2O3_fc, Na2S2O3_volume_spent, blank_volume, sample_weight):
    """
    Function to calculate the iodine index in grams of iodine per 100g
    """
    V_Na2S2O3 = blank_volume - Na2S2O3_volume_spent
    iodine_mols = (Na2S2O3_molarity * Na2S2O3_fc * V_Na2S2O3) / 2
    iodine_mg = iodine_mols * 254 # 254 is the molecular weight of iodine
    iodine_g = (iodine_mg / sample_weight) / 10
    return iodine_g