GB/T 5532-1995 Determination of iodine value of vegetable oils

This standard specifies the reagents, instruments, analytical procedures and result calculation for the determination of iodine value of vegetable oils. This standard does not apply to emulsified fats, such as margarine. GB/T 5532-1995 Determination of iodine value of vegetable oils GB/T5532-1995 Standard download decompression password: www.bzxz.net

GB/T5532-1995
National Standard of the People's Republic of China
Determination of iodine value of vegetable oilswwW.bzxz.Net
Vegetable oils-Determination of iodine value5532-85
GB/T5532-1995
Replaces GB
This standard refers to and adopts the international standard ISO3961:1989 "Determination of iodine value of animal and vegetable oils and fats" 1 Subject content and scope of application
This standard specifies the reagents, instruments, analytical procedures and result calculation used in the determination of iodine value of vegetable oils. This standard does not apply to emulsified fats such as margarine. 2 Reference standards
GB5490 General rules for inspection of grains, oils and vegetable oils Preparation of oil samples
GB/T15687
3 Definition
Iodine value: The mass of iodine absorbed by the sample under the operating conditions specified in this standard. It is expressed in grams of iodine absorbed per 100g of sample.
4 Principle
Dissolve the sample in the solvent and add the wiis reagent. After the specified time, add potassium iodide and water, and titrate the precipitated iodine with sodium thiosulfate solution. 5 Reagents and solutions
The reagents listed in this standard are all analytically pure, and the water is distilled water. 5.1 Potassium iodide solution (100g/L): does not contain iodate or free iodine. 5.2 Starch solution: Mix 5g of soluble starch in 30mL of water, add this mixture to 1000mL of boiling water, boil for 3min and cool.
5.3 Sodium thiosulfate standard solution (0.1mol/L): Preparation and calibration are carried out according to GB5490. Use within 7d after calibration.
5.4 Solvent: A mixture of equal volumes of cyclohexane and glacial acetic acid. 55 Reagent: Acetic acid solution containing iodine monochloride. Weigh 9g of iodine trichloride and dissolve it in a mixture of 700mL of glacial acetic acid and 300mL of cyclohexane. Take 5mL of the above solution, add 5mL of potassium iodide solution (5.1) and 30mL of water, use a few drops of starch solution (5.2) as an indicator, and titrate the precipitated iodine with 0.1mol/L sodium thiosulfate standard solution (5.3), titrating the volume V1. Add 10g of pure iodine to the reagent and dissolve it completely. Titrate as above to obtain V2. Vz/Vi should be greater than 1.5, otherwise a little pure iodine can be added until Vz/Vi slightly exceeds 1.5. After the solution is allowed to stand, pour the supernatant into a stoppered brown reagent bottle and store it away from light. This solution can be stored for several months at room temperature.
6 Instruments and equipment
6.1 Analytical balance: sensitivity 0.1mg.
6.2 Glass weighing blood: suitable for the sample volume and can be placed in a conical flask. 6.3 Conical flask: 500mL capacity, stoppered and completely dry. 7 Sample preparation
Prepare the sample according to GB/T15687.
8 Analysis steps
8.1 Weighing
The mass of the sample varies according to the estimated iodine value, as shown in the following table, estimated iodine value
51~100
101~150
151~200
Sample mass, g
82Put the weighed blood with the sample into a 500mL conical flask, add 20mL solvent (5.4) to dissolve the sample, accurately add 25mL wijs reagent (5.5), cover the stopper, shake well and place the conical flask in the dark. Prepare a blank with the same solvent and reagent but without adding the sample. For samples with an iodine value lower than 150, the conical flask should be placed in a dark place for 1 hour. For samples with an iodine value higher than 150 and substances that have been polymerized or oxidized to a considerable degree, the conical flask should be placed in a dark place for 2 hours. 8.3 Determination
After the reaction time is over, add 20mL of potassium iodide solution (5.1) and 150mL of water. Titrate with the calibrated sodium thiosulfate standard solution (5.3) until it turns light yellow. Add a few drops of starch solution (5.2) and continue titrating until the blue color just disappears after vigorous shaking. 8.4 Number of determinations
The same sample shall be measured twice as specified.
9 Calculation of results
9.1 The iodine value is calculated by the following formula when it is expressed as the number of grams of iodine absorbed per 100g of sample: Iodine value (1.v) = 1269 (VV)
Wherein: C-the standard concentration of sodium thiosulfate solution, mol/L;-the volume of sodium thiosulfate standard solution used in blank test, mL; Vi
V2-the volume of sodium thiosulfate standard solution used in determination, mL; the mass of the sample, g.
9.2 When the results of parallel determinations meet the requirements of the allowable difference, the arithmetic mean value shall be taken as the result. Approved by the State Administration of Technical Supervision on August 17, 1995 and implemented on January 1, 1996
GB/T5532-1995
9.3 Repeatability
The allowable difference of the results of two simultaneous or consecutive determinations of the same sample by the same analyst using the same equipment shall not exceed 0.5 iodine value units.
Additional Notes:
This standard was proposed by the Ministry of Domestic Trade of the People's Republic of China. This standard is under the jurisdiction of the State Grain Reserves Administration. This standard was drafted by the Institute of Cereal Oil Chemistry of the Ministry of Domestic Trade. The main drafter of this standard is Hao Xicheng.
This standard was mainly formulated with reference to AOCS method: Cdl~25. IUPAC method: "Determination of the iodine value (IV)." International Chemical Laboratory Method: "Determination of iodine value using a solvent other than carbon tetrachloride. Approved by the State Bureau of Technical Supervision on August 17, 1995 and implemented on January 1, 1996
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