Scopeia

• Reagent:

• • • Iodine Bromide Solution: Dissolve 20 g of iodine bromide in glacial acetic acid and dilute to 1000 mL with the same solvent.
    • Potassium iodide: Dissolve 80.0 g of Potassium iodide in 1000 mL of water
    • 1 M sodium thiosulfate: Dissolve 25 g of sodium thiosulfate and 0.2 g of sodium carbonate in sufficient carbon dioxide-free water to produce 1000 mL.
    • Starch: Triturate 1.0 g of soluble starch with 5 mL of water and whilst  stirring pour the mixture into 100 mL of boiling water
    • Carbon tetrachloride reagent

 

Iodine value II	Quantity of sample (grams)
Less than 20	1.0
20-60	0.5-0.25
60-100	0.25-0.15
More than 100	0.15-0.10

(Table 1)

• Procedure:.
  • Place a quantity of the test substance, accurately weighed, as specified in the monograph in a dry 300-mL to 500-mL stoppered The quantity of test substance used for the determination depends on the expected value as per table 1
  • Add 15 mL of carbon tetrachloride and dissolve.
  • Add 25 mL of iodine bromide TS, insert the stopper, previously moistened with potassium iodide (80 g/l) TS, shake the flask gently, and keep in the dark for 30 minutes, unless otherwise specified in the monograph
  • Add 20 mL of potassium iodide (80 g/l) TS and 150 mL of water, and, whilst shaking the contents of the flask, titrate with sodium thiosulfate (0.1 mol/l) VS, adding starch TS as indicator towards the end of the titration.).
  • Carry out a blank test under the same conditions (n2 ml of 0.1 M sodium thiosulphate).

Where:

I_I= Iodine Value

n2= End point of blank

n1= End point of test

m= weight in g of substance