GB 5177.4-1985 Determination of the bromine index of industrial alkylbenzenes - Potentiometric titration method

This standard is applicable to the determination of the bromine index of industrial alkylbenzenes. GB 5177.4-1985 Determination of the bromine index of industrial alkylbenzenes Potentiometric titration method GB5177.4-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of bromine index for industrial alkylbenzene--Electrometric titration method This standard is applicable to the determination of the bromine index of industrial alkylbenzene. 1 Principle
UDC 547.52: 543
257.1: 546.14
GB 5177.4-85
Industrial alkylbenzene is dissolved in a specific solvent and titrated with potassium bromide-potassium bromate standard solution. The sudden change in electrode potential caused by a slight increase in the free bromine concentration in the measured solution is the end point of the titration. 2 Definition
Under given conditions, the number of milligrams of bromine consumed by 100g of sample is called the bromine index of the sample. 3 Instruments
3.1 ZD-2 automatic potentiometric titrator (manufactured by Shanghai Second Analytical Instrument Factory) or 25-type acidity meter, equipped with glass electrode and platinum electrode.
3.2 Burette (acid type), 5ml, 10ml, 50ml. 3.3 Tall beaker, 250ml.
3.4 ​​Iodine volumetric flask, 500ml.
3.5 Volumetric flask, 1000ml.
3.6 Measuring cylinder, 10ml, 25ml, 100ml, 250ml. 3.7 Stopwatch.
4 Reagents (all analytical grade)
4.1 Titration solution
Mix the following reagents in order by volume to prepare a 1L solution: glacial acetic acid, 704ml
carbon tetranitride, 134ml
anhydrous methanol (or anhydrous ethanol), 116ml sulfuric acid solution (1:5), 18ml
mercuric chloride methanol solution (100g/L), 18ml potassium bromide aqueous solution (30g/100g water), 10ml4.20.02N potassium bromide-potassium bromate standard solution preparation: dissolve 2.04g potassium bromide and 0.556g potassium bromate in distilled water, dilute to 1L, and store in a brown bottle. Calibration: measure 50ml glacial acetic acid and 1ml hydrochloric acid (specific weight 1.19) in a 500ml iodine volumetric flask. Cool in an ice bath for 10 minutes, take it out, and add 40±0.01ml potassium bromide and potassium bromate solution accurately from a 50ml burette at a speed of about 0.4ml per second while shaking. Immediately cover the bottle with a stopper, shake, and put it in an ice bath. Seal the bottle mouth with 5ml potassium iodide solution. Take it out of the ice bath after 5 minutes and gently lift the stopper. Let the potassium iodide solution flow into the bottle along the wall (do not let the bromine overflow), cover the stopper tightly and shake it vigorously, rinse the stopper and bottle wall with 100ml distilled water, and quickly titrate with sodium thiosulfate standard solution. When it is close to the end point (the solution is light yellow), add 1ml of newly prepared starch indicator solution, and slowly drip until the blue color disappears: National Bureau of Standards 1985~05-10 Issued
1986-01~01 Implemented
GB 5177.4—85
Calculate the equivalent concentration of potassium bromide-potassium bromate standard solution according to formula (1): V.N2
Wherein: N.—equivalent concentration of potassium bromide-potassium bromate standard solution; 40
V——mL of sodium thiosulfate standard solution consumed in titration; N2—equivalent concentration of sodium thiosulfate standard solution used for titration. The difference between the two calibration results is not greater than 0.002N. (1)
4.30.1N sodium thiosulfate standard solution
Dissolve 25g of sodium thiosulfate (NazS2O·5H,Q) in distilled water that has just been boiled and cooled, add 0.01g of sodium carbonate as a stabilizer, dilute to 1L, shake well, and calibrate after leaving for one week. The calibration method refers to the provisions of GB 601-77 "Preparation Method of Chemical Reagent Standard Solution".
.4 Potassium iodide solution
Dissolve 150 g of potassium iodide in distilled water and dilute to 1 L 4.50.25% starch indicator solution.
5 Test procedure
5.1 Preparation
5.1.1 Turn on the ZD-2 automatic potentiometric titrator (3.1) and stabilize the instrument for 15 minutes. To prevent power supply voltage fluctuations, a power stabilizer should be used.
5.1.2 Clamp the indicator electrode (platinum electrode) into the right electrode clamp and connect the wire to the potentiometer terminal. Clamp the reference electrode (glass electrode) into the left electrode clamp and insert the electrode wire plug into the potentiometer jack. The glass electrode should be soaked in distilled water when not in use (new glass electrodes should be soaked in distilled water for 24 hours before use).
5.1.3 Prepare a 5ml (accurate reading to 0.02ml) burette, connect it to the dropper with an acid- and alkali-resistant latex tube, and clip the dropper on the small clip on the right so that the outlet is slightly lower than the platinum sheet of the electrode. 5.2 DeterminationbZxz.net
5.2.1 Weigh a certain amount of sample (accurate to 1mg, refer to Table 1 for sample weight), place it in a tall beaker (3.3), add 100ml titration solution (4.1), and place a 30mm long electromagnetic stirring rod. Place the beaker on the electromagnetic stirrer tray and immerse the electrode in the solution, about 30mm from the bottom of the cup. Start the electromagnetic stirrer and stir for 10 minutes. The stirring speed should be appropriate to avoid bubbles. Table 1 Relationship between bromine index and sample weight
Estimated bromine index range
51~100
100~1000
Sample weight, g
5.2.2 Adjust the instrument zero point to the "7" position. After adjustment, do not move the "calibration button". At the beginning of titration, add 0.1ml potassium bromide and potassium bromate standard solution, record the electromotive force reading after 1 minute, and plot the electromotive force against the number of milliliters titrated. After the potential jump, if the increment of the electromotive force reading does not exceed 10mV after adding 0.1 standard solution for 1 minute, it is considered to have reached the end point. Record the number of milliliters of standard solution consumed. 5.2.3 Blank determination
GB 5177.4-85
Take 100ml of titration solution for blank determination. Change the amount of potassium bromide-potassium bromate solution added each time to 0.02ml, and then titrate to the end point according to 5.2.2.
6 Calculation
Calculate the bromine index according to formula (2):
(A- B) N× 7990
Bromine index=-
Wherein: A——the number of milliliters of potassium bromide-potassium bromate standard solution consumed in titrating the sample; B-
——the number of liters of potassium bromide-potassium bromate standard solution consumed in titrating the blank; N--the equivalent concentration of potassium bromide-potassium bromate standard solution;-the amount of sample weighed,
The arithmetic average of the two determination results is taken as the bromine index of the sample. Divide the bromine index by 1000 to convert it into bromine value. Repeatability
The results measured twice by the same analyst shall meet the requirements of Table 2: Table 2
Australian index range, mg/100g
10~100
100~1000
Additional remarks:
This standard was proposed by the Ministry of Light Industry of the People's Republic of China and is technically managed by 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. The main drafters of this standard are Hu Dehua, You Lintai and Wang Peiwei.
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