HIRANUMA APPLICATION DATA

Automatic Titrator

Data No.

A8Oct. 7,2022

Iodine value measurement for cooking oil

FOOD

1. Abstract
Fatty acid in cooking oil, for example, oleic acid and linoleic acid absorb one or two of iodine molecules.
Other kinds of cooking oils also absorb specific amount of iodine.
Iodine value means the “g” value of halogen which adhere to 100 g of sample; it is defined as indicators
for unsaturated bond components of oils and fat in Pharmacopoeias: JP, USP, and EP.
There are two kinds of measuring methods such as Hanus method and Wijs method for Iodine value
measurement. The former uses iodine bromide and the latter uses iodine chloride as halogen. In this chapter, themeasurement example using more popular Wijs method is introduced.
Excess ICl in regard to the number of double bond is added on Wijs method. One halogen molecule binds
to double bond of oils and fat as the following formula (1).
∣ ∣－C＝C－+ICl→∣ ∣－C－C－∣ ∣I Cl･･･(1)

The Iodine value is determined by excessively-remained ICl which is titrated with sodium thiosulfate
according to the following formula (2).
2Na2S2O3＋ICl→

Na2S4O6＋

NaI ＋ NaCl

2. Configuration of instruments and Reagents(1) Configuration
Main unit：

Hiranuma Automatic Titrator COM series

Electrode：

Platinum combination reference electrode PR-733BZOption：

Buret tip (Tube Type)

Titrant：

0.1 mol/L Sodium thiosulfate standard solution

Additive：

Wijs solution 25 mL(2) Regents

1 mol/L Potassium iodide solution 20 mL
Solvent：

Cyclohexane･･･(2)3. Measurement procedure1) Take about 0.25 g of the sample into an Erlenmeyer flask and weigh it accurately to 0.1 mg digits.
2) Add 20 mL of cyclohexane to dissolve sample.
3) Dispense 25 mL of Wijs solution exactly with volumetric pipette and plug it with a stopper and leave it
under dark room for 30 minutes.
4) Add 20 mL of 1 mol/L potassium iodide solution and 100 mL of pure water.
5) Immerse the electrode and titrate with 0.1 mol/L sodium thiosulfate standard solution.
6) Measure the blank value by testing of (2) ~ (5) without sample.
※The sample size should be changed depending on the iodine value of sample.

4. Measurement conditions and Results
Examples of titration conditions
Measurement of blank
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

1Auto
1
1
mV
10
45
100.10
200
0.20
60

sec
mL
sec
mL
mL
mL

ConstantNo.
SizeBlank
Molarity
Factor
KL

10.0
0.0
0.0
0.0
0.0
0.0

Unit
FormulaDigitsAuto In Pram.

mL
D
3g
mL
mol/L

Mode No.
Pre Int
Del K
Del Sens
Int TimeInt Sens
Brt Speed
Pulse

805053240

Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt Speed
Pulse

805053240sec
mV
sec
mV

Non

Measurement of sample
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

2
Auto
11mV
1015
10
0.1
200
0.20
60

sec
mL
sec
mL
mL
mL

ConstantNo.
SizeBlank
Molarity
FactorKL

20.2573
48.871
0.1
1.004
1.269
0.0

Unit
FormulaDigitsAuto In Pram.

g/100g(B-D)*K*F/S
4g
mL
mol/LsecmV
sec
mV

Non

Measurement results
Measurement
Name

Number ofMeasurements

Size(g)Titration
Value(mL)

Iodine value(g/100 g)

Statistical calculation
results

Blank

1
2――

48.87348.868――Avg.
(Blank)48.871 mL

Sample12
30.25730.26330.247423.52222.86624.387125.5210
125.8350
126.0890

Avg.
SD
CV

125.82 g/100 g
0.28 g/100 g
0.23 %

Measurement of blank

Measurement of sample

Examples of measurement curves

5. Note(1) Adding volume of Wijs solution is 50~60 % excess of requisite amount for sample. Decrease the sample
volume if the Wijs solution is absorbed than above amount.
(2) Timely measure the blank because Wijs solution is easy to degenerate.
(3) Please use Erlenmeyer flask with stopper to avoid sublimation of sample and Wijs solution.
Keyword：Cooking oil, Iodine value, Wijs method, Redox titration*Some measurement would not be possible depending on optional configuration of system.