A. 1 Warning

Some test procedures specified in the test method may lead to hazardous situations. Operators should take appropriate safety and protective measures

A.2 General Provisions

Unless otherwise specified, only reagents confirmed as analytical pure and Grade III water specified in GB/T6682-2008 shall be used in the analysis.

The standard titration solution, impurity determination standard solution, formulation, and product used in the test method shall be prepared in accordance with the provisions of GB/T601, GB/T602, and GB/T603 unless otherwise specified

A.3 Identification Test; Determination of iodine value of fatty acids

A.3.1.1 Reagents and materials

A.3.1.1.1; Carbon tetrachloride

A.3.1.1.2; Potassium iodide solution: 100g/L

A.3.1.1.3 Webster's solution: The preparation method is shown in Appendix B

A.3.1.1.4; Sodium thiosulfate standard titration solution: c (Na2S2O3)=0.1mol/L

A.3.1.1.5 Starch indicator solution: 10g/L

A.3.1.2 Identification Steps

Weigh approximately 0.27g of viscous substance D in A.4.3.2, accurate to 0.0001g, place it in a dry 500mL iodine volumetric flask, and add 10mL of carbon tetrachloride to dissolve.

. Add 25mL ± 0.02mL of Webster's solution, close the bottle cap, seal with potassium iodide solution, and place in a dark place for 30 minutes. Add 15mL of potassium iodide solution and 100mL of water, titrate with sodium thiosulfate standard titration solution until the solution turns light yellow, add 1mL of starch indicator solution, shake vigorously and continue titration until the blue color just disappears, which is the endpoint

At the same time as the measurement, perform a blank test using the same amount of reagent solution without the addition of test materials, following the same steps as the measurement

A.3.1.3 Result Calculation

The iodine value of fatty acids w1 is calculated as iodine, and the value is expressed in grams per hundred grams (g/100g). Calculate according to equation (A.1):

In the equation:

V0- The volume value of the blank consumed sodium thiosulfate standard titration solution (A.3.1.1.4), in milliliters (mL)

V - The volume value of the standard titration solution of sodium thiosulfate consumed by the test sample (A.3.1.1.4), in milliliters (InL)

C - The accurate value of the standard titration solution of sodium thiosulfate, in moles per liter (mol/L)

m - numerical value of the sample mass, in grams (g)

M - The numerical value of the molar mass of iodine, in grams per mole (g/mol) [M=126.9]

Take the arithmetic mean of the results of two parallel measurements as the reported result. The absolute difference between the results of two parallel measurements shall not exceed 0.5 (g/100g) (measured by iodine)

A.3.1.4 Result judgment

The iodine value of fatty acids should be between 80-135 (g/100g) (calculated by iodine).

A.3.2 Polyol Color Test

Take about 2g of the viscous substance E in A.5.2, add 2mL of catechol solution (100g/L) (currently used and prepared), mix well, and then add 5mL of sulfuric acid to mix well, which should show red or reddish brown color

A.4 Determination of Fatty Acids

A.4.1 Method Summary

The sample undergoes saponification hydrolysis, acidification, and generates fatty acids and polyols. The mass of the recovered fatty acids is obtained by repeated extraction separation and concentration drying, and the mass fraction of the fatty acids is calculated by weighing.

A.4.2 Reagents and Materials; Potassium hydroxide

A.4.2.2 Ethanol (95%)

A.4.2.3; Petroleum ether

A.4.2.4 Sulfuric acid solution: 1+2

A.4.3 Analysis Steps

A.4.3.1 Saponification: Weigh approximately 25g of the laboratory sample to the nearest 0.01g. Place in a 500mL flask, add 250mL of ethanol (95%) and 7.5g of potassium hydroxide. Connect the condenser and place it in a water bath for heating and reflux for 2 hours. Transfer the saponified substance to an 800mL beaker, wash the flask with approximately 200mL of water, and transfer to the beaker. Place the beaker in a water bath and evaporate until the ethanol evaporates completely. Adjust the volume of the solution with hot water to approximately 250mL, resulting in solution A

A.4.3.2 Acidification and extraction separation: Add sulfuric acid solution to solution A under heating and stirring to precipitate solidified substances, and then add an excess of about 10% sulfuric acid solution to heat and stir to precipitate oily substances. Transfer this mixture into a 500mL separating funnel and let it stand for layering. Transfer the lower solution to a second 500mL separating funnel, extract it three times with 100mL petroleum ether, and let it stand for layering. Transfer the lower solution B to an 800mL beaker; Combine the petroleum ether extract with the upper layer of oily substance in the first 500mL separating funnel, wash with 100mL water three times. The lower layer of water washing solution is combined with solution B to form solution C, which is used for determining the content of polyols; Transfer the upper layer of petroleum ether mixture into another 800mL beaker, concentrate it on a water bath to about 100mL, and then transfer it to a 250mL beaker with a constant mass at 80 ℃ for evaporation until it becomes viscous. Dry it at 80 ℃ until the mass remains constant to obtain viscous substance D as the mass of the recovered fatty acid. The weighed viscous substance D is used for the determination of the iodine value of fatty acids

A.4.4 Result Calculation

The mass fraction of fatty acids w2 is expressed in%, and calculated according to equation (A.2):

In the equation:

The value of the mass of m1-250mL beaker is in grams (g);

The value of the mass of viscous substance D in the m2 250mL beaker is in grams (g)

m - The numerical value of the sample mass, in grams (g)

Take the arithmetic mean of the results of two parallel measurements as the reported result. The absolute difference between the results of two parallel measurements shall not exceed 1%

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