Iodine value of Oil and Fat by jlhd32

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									 Petroleum                    Iodine value of Oil and Fat
  Redox titration by
      Automatic Potentiometric Titrator
                JIS       K 0070
 Standard       ASTM      D 1959
                ISO       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 :     0.1mol/L sodium thiosulfate (f=1.006)
  Additives :   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 %                 Weather :        Rainy

-Titration parameter-                                                     -Titration curve-
 Model      : AT-510
 Method No. :     10
 Titr.mode : Auto
 Intermit
 Titr.form : EP Stop

                                   [Result parameter]
 [Titration parameter]
                                   <Calculation>
 Form              :   EP Stop     Calc. Type   : Sample
 APB No.           :   1           Conc.1       : Set
 Unit No.          :   1           CO1=
 Detector No.      :   1            (BL1-EP1)*TF*C1*K1/SIZ
  Unit             :   mV                                E
 Max.Volume        :   40.0mL
 Wait Time         :   0s           Unit      : cg/g
 Direction         :   Auto         EP No.    : 1
                                   Temp.Comp. : Off

 [Control parameter]               <Constant>
                                   C1              : 1.269
 End Point No.     :   1           K1              : 1
 End sense         :   Auto
 End Point Area    :   Off         <Titr. Constant>
 Separation        :   Off         Factor       : 1.006
 Over Titr.Vol.    :   0mL         Conc         : 0.1
 Gain              :   1
 Data samp.Pot.    :   4.0mV       <Blank>
 Data samp.Vol.    :   0.5mL       Blank1          : 47.074
 Stability         :   0.5mV/s
 Delay Time        :   1s
 Limit Time        :   30s




(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
          (g)             (mL)             (cg/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】                                【AT-510】                            【AT-500N-1】




Awarded Product of Supreme               • Compact and cost performance      • Low cost and high performance
Technology from Kyoto City                 model                             • Easy view with back light LCD
• Easy key entry by touch panel of       • PC card expands data memory for   • GLP/GMP conformed model
  large color LCD (8-inch wide)            convenience and versatility.
• Simultaneous titration in parallel
• Both potentiometric and Karl
  Fischer      moisture      titration
  (coulometric・volumetric) can be
  performed at a time.




                                                                                           TIB-99424 Ver.01 4/4

								
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