Iodine value of Oil and Fat
Petroleum
Redox titration by
Automatic Potentiometric Titrator
JIS
ASTM
ISO
Standard
K 0070
D 1959
3961
1.Abstract
Test method for measurement of iodine value of fats and oils stipulated in the below
quoted standards is generally practiced by Wijs Method using monobasic iodine,
however, Hanus Method is demonstrated here using iodine bromide.
Firstly, sample fat is dissolved in carbon tetrachloride, and Hanus reagent is added
and left in a dark room for reaction. Then, potassium iodide is added for titration with
0.1mol/L sodium thiosulfate.
The endpoint is the maximum inflexion point on titration curve.
The iodine value of fatty sample is calculated from titration volume of sodium
thiosulfate.
4I2
+
Na2S2O3
＋ 5H2O
→
2NaI
+
２H2SO4
＋ ６HI
2.Reference
1) JIS K 0070-1992 Test Method for Acid value, Saponification number, Ester number,
Iodine number, Hydroxyl value of Chemical products and Unsaponifiable matter
2) ASTM D 1959-97 Standard Test Method for Iodine Value of Drying Oils and
Fatty Acids
3) ISO 3961:1996 Animal and vegetable fats and oils – Determination of iodine
value
3.Cautions in measurement
1) Reagent and additives must be handled in a well ventilated room or in a draft.
2) Blank test is required as necessary.
3) Use a 300mL conical flask with ground-in stopper to avoid sublimation of iodine
when the sample and Hanus solution react.
TIB-99424 Ver.01 1/4
4.Post-measurement care
Rinse the electrode with pure water, and keep it dipped in water to avoid drying up.
5.Test equipment
Main unit: Automatic potentiometric titration system (preamplifier: STD)
Electrode: Option Combination platinum electrode
6.Reagent
Reagent ：
Additives ：
0.1mol/L sodium thiosulfate （ｆ＝1.006）
Pure water, Carbon tetrachloride, Hanus solution,
15% Potassium iodide
7.Measurement procedure
―Measurement―
1) Deliver 0.1g sample to a 300ｍL conical flask with ground-in stopper. Add
20.0mL carbon tetrachloride and seal. Dissolve in an ultrasonic washing
machine.
2) Add 25.0mL Hanus solution, and seal. Shake for one minute.
3) Keep it sealed and leave in a dark room (about 20°C) for 30 minutes.
4) Add 10.0mL of 15% potassium iodide and 100ｍL water, and seal. Shake for 30
seconds.
5) Titrate with 0.1mol/L sodium thiosulfate to obtain iodine value.
Likewise, perform blank test to obtain blank level.
8.Formula
Iodine value ( cｇ / g ) = ( BL1 － EP1 ) × TF × C1 ×K1 / SIZE
EP1 ： Titration volume ( mL )
BL1 ： Blank level ( 47.074mL )
TF
： Factor of titrant ( 1.006 )
C1
： Concentration conversion coefficient ( 1.269 )
(Atomic mass of iodine: 126.9/100)
K1
： Unit conversion coefficient ( 1 )
SIZE ： Sample size (ｇ)
TIB-99424 Ver.01 2/4
9.Example of measurement
－Ambient condition－
Room temperature：23 ℃
Humidity ：
23 ％
-Titration parameterModel
: AT-510
Method No. :
10
Titr.mode : Auto
Intermit
Titr.form : EP Stop
Weather ：
Rainy
-Titration curve-
[Result parameter]
[Titration parameter]
Form
APB No.
Unit No.
Detector No.
Unit
Max.Volume
Wait Time
Direction
:
:
:
:
:
:
:
:
EP Stop
1
1
1
mV
40.0mL
0s
Auto
[Control parameter]
End Point No.
End sense
End Point Area
Separation
Over Titr.Vol.
Gain
Data samp.Pot.
Data samp.Vol.
Stability
Delay Time
Limit Time
:
:
:
:
:
:
:
:
:
:
:
1
Auto
Off
Off
0mL
1
4.0mV
0.5mL
0.5mV/s
1s
30s
<Calculation>
Calc. Type
: Sample
Conc.1
: Set
CO1=
(BL1-EP1)*TF*C1*K1/SIZ
E
Unit
: cg/g
EP No.
: 1
Temp.Comp. : Off
<Constant>
C1
K1
: 1.269
: 1
<Titr. Constant>
Factor
: 1.006
Conc
: 0.1
<Blank>
Blank1
: 47.074
(The above printout data are obtained from titration by AT-510 unit)
≪Titration parameter≫
Form: of titration / APB No. the burette used in titration / Unit No.: APB Unit File number
Detector No.: the detector used in titration/ Unit of potential / Max Volume: of titration
Wait Time: before titration starts/ Direction.: of titration
≪Control parameter≫
End Point No.: number of EPs / End sense: of EP detection / End Point Area: EP detection area
Separation: of potential / Over Titr.Vol. over-titrated volume / Gain: sensitivity of detection signal
Data samp.Pot.: potential change of sampling signal / Data samp.Vol. : titration volume of sampling signal
Stability: of EP potential / Delay Time: before stability check / Limit Time: of stability check
≪Calculation parameter≫
Calc.Type: of formula / Conc.1 formula 1 / Unit: of results
EP No. of calculation / Temp.Comp.: temperature compensation / C1(mg/mL): concentration conversion coefficient
K1: unit conversion coefficient / Factor: factor of titration liquid / Blank1: blank level 1
TIB-99424 Ver.01 3/4
－Measurement results－
Sample
Titration
Iodine value
n
Iodine value
(mL)
(cg/g)
（g）
1
0.3096
23.5860
96.851
Mean
97.205 cg/g
2
0.3122
23.1431
97.855
SD
0.5634 cg/g
3
0.3100
23.5413
96.910
RSD
0.5796 %
＊The above test results are obtained by 3 tests of the same sample.
＊ Red underline shows the data from page 3/4.
10.Summary
The iodine value is expressed in grams of iodine for the amount of halogens linked with
100g test sample, and is used as degree of unsaturated bond of fats and oils.
Iodine value is used to compare the number of C=C contained in natural complex
mixture.
Measurement results this time shows favorable repeatability with 0.6% relative
standard deviation. Precise and reliable measurement is assured by the automated
potentiometry.
The iodine value of fats and oils can be perfectly measured by any of the following
titration systems manufactured by Kyoto Electronics (KEM).
【AT-610】
Awarded Product of Supreme
Technology from Kyoto City
• Easy key entry by touch panel of
large color LCD （8-inch wide）
• Simultaneous titration in parallel
• Both potentiometric and Karl
Fischer
moisture
titration
(coulometric・volumetric） can be
performed at a time.
【AT-510】
• Compact and cost performance
model
• PC card expands data memory for
convenience and versatility.
【AT-500N-1】
• Low cost and high performance
• Easy view with back light LCD
• GLP/GMP conformed model
TIB-99424 Ver.01 4/4