GB/T 3781.7-1993 Determination of iodine absorption value of acetylene black
Some standard content:
National Standard of the People's Republic of China
Acetylene black-Determiation of iodine absorption number
This standard adopts the international standard ISO1304-1985 "Determination of iodine absorption number of carbon black". 1 Subject content and scope of application
This standard specifies the method for determining the iodine absorption number of acetylene black. This standard is applicable to the determination of the iodine absorption number of acetylene black. 2 Principle
GB/T 3781. 7--93
Replaces GB 3781. 7--83
The acetylene black sample is dried, weighed and vigorously mixed with a certain volume of iodine standard solution, and then the mixture is centrifuged. Take a certain volume of the separated clear iodine solution and titrate it with a standard sodium thiosulfate solution. Calculate the iodine absorption number of acetylene black from the titration value and the sample weight.
3 Reagents
Iodine (GB675): analytical grade.
Potassium iodide (GB1272): analytical grade.
Sodium thiosulfate (NazS,O,·5H,O, GB637): analytical grade. 3.4
Potassium iodate (GB 651): reference reagent.
Mercuric iodide: analytical grade.
Sulfuric acid (GB 625): specific gravity 1.84, analytical grade. 3.7 Soluble starch analytical grade.
Test water: should meet the requirements of GB6683.3 grade water, fresh distilled water or water of equivalent purity prepared by other methods, 4 Instruments
Analytical balance: accurate to 0.1mg.
Constant temperature drying oven; can be controlled at 105±2℃
Electric oscillator international type or Kang's.
Electric centrifuge: speed above 1000r/min. 4.4
4.5Pipette without graduation, 50mL.20mL. 4.6Filled tube 50mL, 25mL.
Volume flask: with stopper, 1000 ml.
4.8.Angle flask: with stopper 125mL.150mL.250mL. 4.9
Funnel: short neck diameter 75mm.
Centrifuge tube.
Approved by the State Technical Supervision Commission on March 3, 1993 and implemented on December 1, 1993
5 Preparation and calibration of solution
5.1 Starch indicator: 2.5g/1k
CB/T 3781. 7-93
Weigh 2.5g of powdered soluble starch and 2mg of mercuric iodide, put them in a 50tnL beaker, add 25ml of water and stir evenly, immediately pour the above starch/mercuric iodide suspension into 1000mL of boiling water, stirring at the same time, boil for not less than 10min to ensure full dissolution. Then cool to room temperature and pour the upper clear solution into a cold glass bottle. 5.2 Potassium iodate/potassium iodide solution: c(1/6K1O,)=0.0394) mol/L 5.2.1 Place an appropriate amount of potassium iodate in a drying oven (4.2) at 125±1°C for 1 h, then transfer to a dryer 1 and cool to room temperature. 5.2.2 In a 1000ml volumetric flask, dissolve 45% potassium iodide in about 200ml of water, then add 1.4058 freshly dried potassium iodate (5.2.1). Accurate to (0001g, when completely dissolved, dilute with water to 1000mL. 5.3 Sodium thiosulfate solution: c(1/2NaS,0,) = 0.03941ml/L. 5.3.1 Preparation Weigh 9.79g of sodium thiosulfate (NaS.0,·5H,0) containing 5 % water, accurate to 0.005g, dissolve in about 500ml steaming water in a 1000mL volumetric flask, add 5ml, n-pentanol or 0.01 mercuric iodide, shake the solution in the volumetric flask to mix thoroughly. Add water Dilute to 100mL, and shake the solution in the flask vigorously to ensure uniform dilution. 5.3.2 Calibration: After standing for 24h, use potassium iodate/potassium iodide solution (5.2) to calibrate the sodium thiosulfate solution (5.3), and proceed as follows
Accurately pipette 25mL of potassium iodate/potassium iodide (5.2) into a 250mL conical flask, add 3mL. About 20% (m/m) a.
sulfuric acid solution to free iodine, and titrate with sodium thiosulfate solution until it turns light yellow, then add about 5mL of starch solution (5.1) and continue titrating until the color of the sodium thiosulfate solution changes from pale yellow to colorless after adding 1 drop of sodium thiosulfate solution. This is the end point. The reading of the burette should be accurate to 0. ol mL
Calculate the concentration of sodium thiosulfate solution according to formula (1): b.
25 X 0. 039 41
Wherein: V,—volume of sodium thiosulfate solution consumed in titration, mL. Note: The concentration coefficient is 25/V and can be adjusted to 1. if necessary. 5.4 Iodine standard solution: c(1/21,)-(. 047 28 mol/L. 5.4.1 Preparation: 1.0 part iodine is prepared with 9.5 parts potassium iodide into a 0.04728 mol/1. solution. ()
Weigh 57.00± potassium iodide to the nearest 0.01g, transfer it to a 1000mL volumetric flask, add about 3mL of distilled water to dissolve it, quickly weigh 5.01g iodine to the nearest 0.005g, quickly transfer it to the above volumetric flask and slowly dilute it to 1 with distilled water. 000 mL,
5.4.2 Calibration: After placing the iodine solution recorded above for 24 hours, use the marked sodium thiosulfate solution to calibrate the iodine solution (5.4). Follow the steps below:
a. Use a pipette to accurately absorb 25 mL of the iodine solution to be calibrated and transfer it to a 250 mL conical flask. b. Use the calibrated sodium thiosulfate solution (5.3) to titrate the iodine solution in the conical flask. When the yellow color of iodine is almost gone, add about 1 ml of starch solution (5.1) and continue titrating until the blue color disappears. c. Calculate the concentration of the iodine solution e2 according to formula (2):
Wherein: V, volume of sodium thiosulfate solution consumed in titration, mL; c. - concentration of sodium thiosulfate solution, mol/LWhen the concentration of the prepared iodine solution is higher than the required concentration, the volume of water to be added when adjusting to the required concentration can be determined by formula (3):
GB/T 3781:7-93
Y,xca-V
Formula t: V - volume of iodine solution before adjustment, mL; F - concentration of iodine solution before adjustment, mol/L: :
-specified concentration of iodine solution (-
-12)=0). 047 28 mol/L.
Add the required amount of distilled water calculated by formula (3) to the iodine solution, plug the bottle tightly, and shake to ensure uniform dilution. ：(D) The concentration of iodine solution should be within the range of e(-
-1)=0.04723~=0.04733mol/1., so that the iodine solution can be calibrated to ±0.00005mol/L. All reagents should be stored in brown glass bottles with stoppers in a dark cabinet before use. 6 Test conditions
The test is preferably carried out in a laboratory with a temperature of 23 ± 2°C and a relative humidity of (50 ± 5)% (arbitration conditions) or a temperature of 27 ± 2. Relative humidity (65 + 5).
It is recommended that the instruments and reagents used should be equilibrated at room temperature for at least several hours before use. In the laboratory, there should be no smoke or steam that may affect the test results. 7 Steps
7.1 Place an appropriate amount of sample in a constant temperature drying oven (4.2) at +105 ± 2°C and dry for 1 hour. Transfer to a desiccator and cool for later use. 7.2 Weigh 0.5 g of the above-dried sample, accurate to 0.0002 g, place it in a clean, well-ventilated conical flask, and use a pipette to accurately add 50 ml.t:(
1.)=(0.04728mol/L iodine standard solution, immediately plug the bottle tightly. 7.3 Shake by hand for 2min (100-120 times/min) or oscillate on an electric oscillator for 2min. Let stand for 5min, filter through a glass ladder by pouring method or centrifuge in an electric centrifuge at a speed of 1 000 r/min for 3min. 7.4 Discard the initial filtrate 3-5ml., accurately draw 20ml. of filtrate with a pipette, and inject it into another clean conical flask. 7.5 Titrate with sodium thiosulfate standard solution with c(Na,S,0,)=0.03941mol/L. When the solution turns light yellow, add 3-5mL of starch indicator (5.1), and continue titrating until the blue turns colorless, which is the end point. 7.6 Perform a blank test at the same time.
8·Result expression
8. 1 The iodine absorption value of the sample 1 (g/kg) is calculated by formula (4): I = (V - V,) X.126. 9c)
I - 317.2(V+ - V,) 1
Wherein, V:
The volume of sodium thiosulfate solution consumed in titrating the empty iodine solution, mLV.…The volume of sodium thiosulfate solution consumed in titrating the sample iodine solution, mL..c1-The concentration of sodium thiosulfate solution, mol/L.; The mass of the test partner·g.
When the mass of the acetylene black sample is 0.5g, the formula is simplified to formula (6): (V- Va) × 25.0 × concentration coefficient (4)
GB/T 3781.7-93
The concentration coefficient in formula (6) is shown in the note in 5.3.2. The calculation result is rounded to the integer.
8.2 Allowable difference
The difference between the two determinations of fruit shrinkage shall not exceed 2 g/kgTest report
The test report shall include the following items:
The national standard number on which this test is based,
The type and mark of the sample;
The average value of the two determination results;
Test conditions:
Test date. www.bzxz.net
Additional remarks:
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Carbon Black Industry Research and Design Institute of the Ministry of Chemical Industry. This standard was drafted by the Carbon Black Industry Research and Design Institute of the Ministry of Chemical Industry. The main drafters of this standard are Yu Lian, Yu Chuanying, and Guo Boqi.
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