GB/T 9104-2008Test methods for industrial stearic acids (English PDF)

3.1 Iodine value

halogen absorbed by 100g of stearic acid sample, expressed in equivalent amount of iodine

3.2 saponification value under the specified test conditions, the number of milligrams of potassium hydroxide consumed to saponify 1g of stearic acid sample

3.3 acid value the number of milligrams of potassium hydroxide consumed to neutralize 1g of stearic acid sample

4.2.8 Starch indicator solution (10g/L): is prepared according to 5.3 in QB/T

2739-2005.

4.2.9 Sodium thiosulfate (GB/T 601), c(Na2 S 2 O 3 ) = 0.1mol/L standard titration solution, is prepared and calibrated according to 4.12 in QB/T 2739-2005.

4.2.10 Iodine chloride solution (Wijs solution): dissolve 13g of iodine (4.2.6) in

1000mL of acetic acid (4.2.1) (slightly heat while dissolving). Then place in a

1000mL brown bottle. After cooling, pour 100mL~200mL into another brown bottle. Place in a dark place for adjustment use. Make chlorine (4.2.7) access to the remaining 800mL~900mL of iodine solution until the solution gradually fades from a dark color till it appears orange and transparent. After the access amount of chlorine is corrected according to the correction method, use the preserved iodine solution to adjust.

Correction method: Respectively take 25.0mL of iodine solution and the freshly- prepared Wijs solution. Respectively add 20mL of potassium iodide solution (4.2.2). Then respectively add 100mL of distilled water. Use 0.1mol/L sodium thiosulfate standard titration solution (4.2.9) to titrate the solution. When it appears light yellow, add 1mL of starch indicator (4.2.8) to continue titrating until blue disappears. The volume of sodium thiosulfate standard titration solution consumed by freshly-prepared Wijs solution shall be close to twice iodine solution's volume.

4.3 Apparatus

Common laboratory apparatus and

4.3.1 Iodometric flask: 250mL.

4.3.2 Plugged burette: 25mL, brown.

4.3.3 Volumetric flask: 1000mL, brown.

4.3.4 Pipette: 10mL, 25mL.

4.4 Test procedures

Weigh 2g~3g of dry sample (to the nearest of 0.001g; according to the level of iodine price, the weighing can be increased or decreased) in the iodometric flask (4.3.1). Add 20mL of cyclohexane-acetic acid solution (4.2.4). After the sample is dissolved, use pipette (4.3.4) to add 25.0mL of Wijs solution (4.2.10).

Completely shake well and place at a dark place around 25°C to store for 30min.

Then take the iodometric flask out from the dark place. Add 20mLof potassium iodide solution (4.2.2). Then add 100mL of distilled water. Use sodium thiosulfate standard titration solution (4.2.9) to titrate. Perform titration while shaking till the solution appears light yellow. Add 1mL of starch indicator solution

5.2 Apparatus

Common laboratory apparatus and

5.2.1 Erlenmeyer flask: 250mL.

5.2.2 Plugged burette: 50mL.

5.2.3 Constant-temperature water bath or hot plate.

5.3 Test procedures

Weigh 2g of specimen (to the nearest of 0.001g) in the Erlenmeyer flask (5.2.1).

Use pipette to add 50.0mL of potassium hydroxide ethanol solution (5.1.1).

Then install a reflux condenser. Place in water bath or hot plate (5.2.3) to maintain the slight boiling state for 1h. Do not allow vapor to escape from the condenser. After removing, add 6 drops of phenolphthalein indicator solution (5.1.3). While it is still hot, use hydrochloric acid standard titration solution (5.1.2) to titrate till red just disappears. Conduct the blank test at the same time.

5.4 Result calculation

5.4.1 The saponification value of stearic acid (SV) is expressed in milligrams per gram (mg/g). It is calculated according to formula (2):

Where,

V 2 - Volume of hydrochloric acid standard titration solution consumed by blank test, in milliliters (mL);

V1 - Volume of hydrochloric acid standard titration solution consumed by test portion, in milliliters (mL);

c - Concentration of hydrochloric acid standard titration solution, in Moores per liter (mol/L);

56.1 - Molar mass of potassium hydroxide expressed by grams in test, in grams per millimoles (g/mmol);

m - Mass of test portion, in grams.

Use the arithmetic mean of the results of two parallel measurements to indicate to one digit after the decimal point as the determination result.

5.4.2 Precision: The absolute difference between two independent test results

per liter (mol/L);

56.1 - Molar mass of potassium hydroxide expressed by grams in test, in grams per millimoles (g/mmol);

m - Mass of test portion, in grams (g).

Use the arithmetic mean of the results of two parallel measurements to indicate one digit after decimal place, as determination result.

6.4.2 Precision: The absolute difference between two independent test results

obtained under repetitive conditions is not more than 0.5mg/g. The premise is that the situation greater than 0.5mg/g does not exceed 5%.

7.1 Principle

Since fatty acid and platinum-cobalt standard color have similar spectral absorption characteristics, use a spectrophotometer, at a certain wavelength, to determine a range of standard chromatic absorbances and draw the working curve. At the same wavelength, determine the absorbance of specimen.

Compare with the drawn working curve, find the corresponding fatty acid color value. Use platinum-cobalt color unit (Hazen) to express.

7.2 Reagents

7.2.1 Cobalt chloride hexahydrate (CoCl 2 ·6H 2 O) (GB/T 1270).

7.2.2 Potassium chloroplatinate.

7.2.3 Hydrochloric acid (GB/T 622), density (rho 20 ) is about 1.19g/mL.

7.3 Apparatus

Common laboratory apparatus and

7.3.1 Spectrophotometer, wavelength range is 360nm~800nm, with a 10cm cuvette.

7.3.2 Constant-temperature water bath.

7.3.3 Beaker, 50mL.

7.3.4 Volumetric flask, 1000mL.

7.4 Procedures

6 - water bath;

7 - solidification tube;

8 - wild-mouth bottle;

10 - heavy object;

11 - beaker.

Figure 1 -- Apparatus for determination of titer

8.1.1 Thermometer: 50°C~100°C; division is 0.1°C; calibration required.

8.1.2 Solidification tube: diameter is about 25mm; the length is 100mm; there is a scale at a position 57mm from the bottom; the tube mouth is equipped with a soft cork; the soft cork has two holes; the middle hole is inserted into the thermometer and the other hole is inserted into glass (or stainless steel) blender.

8.1.3 Wide-mouth bottle: 450mL; the inner diameter of the bottle neck is about

38mm; the bottle mouth is equipped with a soft cork of which the diameter is

25mm hole.

8.1.4 Blender: glass or stainless steel; the lower end is bent into a ring of which the diameter is 20mm to be perpendicular to the rod.

8.2 Procedures

Melt about 30g of specimen to make its temperature at least 10°C higher than titer. Place in the solidification tube to the scale. Insert the thermometer and the blender to make the mercury ball of the thermometer about 45mm below the scale.

Place the solidification tube in the wide-mouth bottle that has a soft cork, as shown in Figure 1. Keep the water bath temperature at around 30°C. Use the blender that is set on the thermometer, at an amplitude of about 40mm up and down, to evenly stir (about 80 times/min ~ 100 times/min). And observe the temperature. When the temperature stops dropping for 30s, immediately stop stirring. Carefully observe the sudden rise of temperature.

8.3 Result expression

8.3.1 The highest temperature of rise shall be the titer of this specimen.

Use the arithmetic mean of the results of two measurements to indicate to one digit after the decimal point, as the determination result.

8.3.2 Precision: The absolute difference between two independent test results

obtained under repetitive conditions is not more than 0.2°C. The premise is that the situation greater than 0.2°C does not exceed 5%.

10.1.2 Sulfuric acid c(H 2 SO4 ) = 0.001% standard solution.

Measure 6.0mL of sulfuric acid (10.1.1). Slowly pour in a small amount of distilled water. Then dilute to 1000mL [c 0 (H 2 SO4 ) ~ 0.1mol/L]. Calibrate according to 4.4 in QB/T 2739-2005.

Use sulfuric acid that has been calibrated to calculate the number of milliliters of sulfuric acid solution required according to 1/[c(H 2 SO4 )×0.98]. Measure the calculated volume of sulfuric acid solution. Pour into a 250mL volumetric flask.

Use distilled water to dilute to the scale. Completely shake well. Then pipette

25.0mL to pour into a 1000mL volumetric flask. Use distilled water to dilute to the scale. Mix well and it shall be 0.001% standard solution.

10.1.3 Methyl orange indicator solution (1g/L), is prepared according to 5.15 in

QB/T 2739-2005.

10.2 Apparatus

Common laboratory apparatus and 5mL tube (glass one needs to be colorless).

10.3 Procedures

Weigh 5g of specimen (to the nearest of 0.1g) in a clean and dry 50mL beaker.

Heat it to make it melted. Use a measuring cylinder to add 5mL of boiled distilled water. Heat to stir for 5min. Cool to solidify stearic acid. Take out the stearic acid block. Pour the solution into a tube. Add one drop of methyl orange indicator solution (10.1.3). In another tube, add an equal volume of 0.001% sulfuric acid standard solution (10.1.2) and equivalent indicator.

10.4 Result expression

Visually compare the color of the two. The color of specimen solution is not darker than that of sulfuric acid standard solution. It is considered that the inorganic acid is less than 0.001%.

11.1 Apparatus

Common laboratory apparatus and

11.1.1 Porcelain crucible: 50mL.

11.1.2 Dryer: built-in color changing silicone.

11.1.3 High temperature electric furnace: temperature can be controlled; can be heated to 1000°C.

12.2.3 Sulfuric acid (GB/T 625): density (rho 20 ) is about 1.84g/mL.

12.2.4 Ether (GB/T 12591).

12.2.5 Carrier gas: nitrogen.

12.2.6 Combustion gas: hydrogen.

12.2.7 Combustion-supporting gas: air; is supplied by a steel cylinder or air compressor and is purified.

12.3 Apparatus

Common laboratory apparatus and

12.3.1 Gas chromatograph: with flame ionization detector, temperature

programmer.

12.3.2 Chromatographic column: filled column; the length is 2m~3m; the inner diameter is 3mm~4mm; with built-in stationary phase (for example, DEGS is coated on an 80 mesh ~ 100 mesh white carrier).

12.3.3 Data processor or spectrum workstation.

12.3.4 Micro-sampler: 1µL.

12.3.5 Volumetric flask: 5mL.

12.4 Procedures

12.4.1 Determination of chromatographic conditions

a) Column temperature: depend on the chromatographic column used;

DEGS column temperature is 180°C;

b) Programmed temperature rise operation: initial temperature is

150°C~180°C; heating rate is 3°C/min~5°C/min; final temperature is

200°C~240°C;

c) Vaporization chamber temperature: 300°C;

d) Detector temperature: 300°C;

e) Carrier gas flow rate: about 30mL/min~50mL/min.

12.4.2 Spectrum analysis

12.4.2.1 Methyl esterification

Take about 0.1g of specimen in a 5mL volumetric flask (12.3.5). Add 2mL~3mL