GB/T 9104.1-1988 Test method for industrial stearic acid - Determination of iodine value

GB/T 9104.1-1988 Test method for industrial stearic acid Determination of iodine value GB/T9104.1-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test methods for industrial stearic acids-Determination of iodine value1 Subject content and scope of application
This standard specifies the method for the determination of iodine value of industrial stearic acid. UDC 668.1.012
：543.06
GB 9104.1-—88
This standard is applicable to the determination of iodine value of industrial stearic acid produced by pressing or steaming after hydrolysis of animal and vegetable fats and oils. 2 Principle
Use iodine chloride to react with the unsaturated acid in stearic acid, then use sodium thiosulfate to titrate the excess iodine chloride and iodine molecules, calculate the volume of sodium thiosulfate solution equivalent to the iodine chloride consumed by the unsaturated acid reaction in stearic acid, and then calculate the iodine value (iodine value refers to the halogen absorbed by 100g of stearic acid sample, expressed in grams of equivalent iodine). The reaction formula is as follows: Iz +Clz --2ICI
RCH · CHR,+ICI→RCHI·CHCIR2ICI+KI-
→KCI+I2
I2+2NazS,O:+2NaI+Na2S,O
3 Reagents
The reagents used should be analytical grade, and the water should be distilled water. 3.1 Glacial acetic acid (GB676)
3.2 Potassium iodide (GB1272) 15% aqueous solution
3.3 Hydrochloric acid (GB622) (density D21.19g/mL)3.4 Chloroform (GB682) or carbon tetrafluoride (GB688)3.5 Iodine (GB675)
3.6 Chlorine (HG 1--31) 99.8%
Or prepare by adding hydrochloric acid with a density of 1.19g/mL dropwise to potassium permanganate, and then drying the generated chlorine through a gas washing bottle containing sulfuric acid with a density of 1.84g/mL. 3.7 Iodine nitride
3.8 Starch indicator solution
Weigh 18 soluble starch, add a little distilled water and stir to make a paste, then add 100mL of freshly boiled distilled water and stir rapidly. Cool to room temperature and set aside. Www.bzxZ.net
3.9 Potassium dichromate (GB601) c(
-K,Cr,O,) = 0. 1 mol/L standard solution. 3.10 Sodium thiosulfate (GB601) c(Na2S,O3) = 0.1 mol/L standard solution. 3.11 Iodine chloride solution
Approved by the Ministry of Light Industry of the People's Republic of China on April 30, 1988, implemented on October 1, 1988
GB 9104.1—88
Dissolve 16.24g of iodine fluoride in 1000mL of glacial acetic acid, or prepare it according to the preparation method of Wei's solution, that is, dissolve 13g of iodine in 1000mL of glacial acetic acid (slightly heat it during dissolution), and then place it in a 1000mL brown bottle. After cooling, pour out 100~200mL into another brown bottle and place it in a dark place for adjustment. Fluorine gas is introduced into the remaining 800-900 mL of iodine solution until the solution gradually fades from dark to orange-red and transparent. The amount of chlorine introduced is calibrated according to the calibration method and adjusted with the previously reserved sulfonic acid solution. Calibration method: Take 25 mL of iodine solution and 20 mL of newly prepared Wei's solution, respectively, and add 100 mL of distilled water to each. Titrate with 0.1 mol/L sodium thiosulfate standard solution until the solution turns light yellow, add 1 mL of starch indicator solution, and continue to titrate until the blue disappears. The volume of 0.1 mol/L sodium thiosulfate standard solution consumed by the newly prepared Wei's solution should be close to twice that of the iodine solution. 4 Apparatus
4.1 Iodine volume flask 250mL
4.2 Burette 25mL, brown
4.3 Pipette
4.4 Volumetric flask
1000mL, brown
5 Test procedure
Accurately weigh 2-3g of dry sample (the amount can be increased or decreased according to the iodine value), place it in an iodine volume flask (4.1), and add 15mL of chloroform or carbon tetrachloride. After the sample is dissolved, add 25mL of iodine chloride solution (3.11) with a pipette, shake well, and place in a dark place at about 25℃ for 30min. Take the iodine volume flask out of the dark, add 20mL of potassium iodide solution (3.2), then add 100ml of distilled water. Titrate with sodium thiosulfate standard solution (3.10), shake and titrate until the solution turns light yellow, add 1mL of starch indicator solution, and continue titrating until the blue disappears. At the same time, perform a blank test under the same conditions. 6 Calculation of results
I.V = (BS) ×C× 0.1269 × 100m
Where: 1.V—iodine value.g/100g,
B—volume of sodium thiosulfate standard solution consumed in blank test, mL, S-volume of sodium thiosulfate standard solution consumed in sample test, mL; C-concentration of sodium thiosulfate standard solution, mol/L, m-
mass of sample·g
0.1269-millimolar mass of iodine atom, g/mmol. The permissible error of the parallel test results is 0.05. Additional Notes:
This standard was proposed by the Ministry of Light Industry of the People's Republic of China and is under the jurisdiction of the Daily Chemical Industry Scientific Research Institute of the Ministry of Light Industry. This standard was drafted by the Daily Chemical Industry Scientific Research Institute of the Ministry of Light Industry. This standard is equivalent to the determination of iodine value in the Japanese Industrial Standard JISK 3331 "Industrial Hardened Oil Fatty Acids". 102
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