This standard specifies the method for determining the fluorine content of flexible graphite sheets by alkali fusion and ion selective electrode method. This standard is applicable to the determination of the fluorine content of flexible graphite sheets, and the determination range is 1~1000ppm. JB/T 7758.1-1995 Method for determining the fluorine content of flexible graphite sheets JB/T7758.1-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T7758.1-95
Flexible Graphite Sheet
Published on June 16, 1995
Determination Method of Fluorine Content
Implementation on July 1, 1996
Ministry of Machinery Industry of the People's Republic of China
Mechanical Industry Standard of the People's Republic of China
Flexible Graphite Sheet
1 Subject Content and Scope of ApplicationWww.bzxZ.net
Determination Method of Fluorine Content
JB/T 7758.195
This standard specifies the determination method of fluorine content of flexible graphite sheet by alkali fusion and ion selective electrode method. This standard is applicable to the determination of fluorine content of flexible graphite sheet, and the determination range is 1 to 1000ppm. 2 Method Summary
The sample is filtered after melting and decomposing sodium hydroxide. The complex ion strength adjustment wave is added to the filtrate, and the pH value is adjusted to 5-6 with hydrochloric acid. The electrode potential in the test solution is directly measured using a cutting electrode and a galvanneal electrode as a reference electrode, and the fluorine is quantified using the standard curve method. 3 Reagents and Materials
3.1 Sodium hydroxide (superior grade).
3.2 Sodium oxynitride solution: C(NaOH)=5mol/L3.3 Hydrochloric acid solution (1+2).
3.4 ​​Dilute hydrochloric acid solution: C(HCl)=1mol/L. 3.5
Bromocresol green indicator (0.1%).
Complex ion strength adjustment solution: C(Na,C,H,O,·2H,O)=0.3mol/LC(KNO,)z0.2mol/L. 3.6
3.6.1 Weigh 88.2g sodium citrate and 20g potassium nitrate and dissolve them in 500mL water. 3.6.2 Add 0.5mL bromocresol green indicator and adjust the pH value with hydrochloric acid (3.4) until the indicator begins to turn blue-green. Add 1 drop of sodium fluoride (3.2) to turn it back to jade blue (the pH value is about 6.5 at this time), and dilute the solution to 1000mL. 3.7 Fluorine standard solution
3.7.1 Fluorine standard solution: Weigh 0.2210g sodium fluoride (superior purity) that has been dried at 105℃ for 2h and dissolved in water, transfer to a 100mL volumetric flask and dilute to the mark with water. Mix and transfer to a plastic bottle (each mL of this solution is equivalent to 10004g fluorine). Store in a refrigerator. 3.7.2 Fluorine standard solution: Accurately pipette 10.0mL of fluorine stock solution into a 100mL volumetric flask before use, add water to the mark, and mix well (each mL of this solution is equivalent to 100g fluorine).
3.7.3 Fluorine standard dilute solution: Accurately pipette 10.0mL of standard solution into a 100mL volumetric flask, add water to the mark, and mix well (each mL of this solution is equivalent to 10ug fluorine).
3.8 Nickel crucible, 25mL.
4 Instruments and equipment
Oxygen ion selective electrode. Measuring range is 10-1～5×10mol/L, CSB-F-1 type or equivalent electrode. 4.1
Ratio electrode, 232 type or equivalent saturated glycine multiplication electrode. 4.2
Acidity meter, measuring range 0~14pH. PHS-2 type or equivalent acidity meter. 4.3
Potentiometer, measuring range 0~1400mV.
Avoid force agitator.
Approved by the Ministry of Machinery Industry on 1995-06-16
Implemented on 1996-07-01
5 Sample preparation
JB/T7758.195
5.1 Collect representative samples, weighing not less than 20 grams, with clean surfaces and no oil or dust. 5.2 Take three square samples of the same size at equal distances along the diagonal direction of the plate, weighing not less than 5g. 5.3 Cut the sample into pieces with stainless steel scissors, then dry it in an oven at 105~110℃ for 1h, and then cool it in a dryer for use. 6 Determination steps
6.1 Preparation of test solution
6.1.1 Weigh 0.5g of sample into nickel-coated tube, add 4g of sodium hydroxide, stir slightly with a spoon, cover the tube with a lid and place in a muffle furnace. Heat to 500℃ and melt for 20min, take out the tube and cool. 6.1.2 Soak in hot water and wash out the melt with water into a 100mL beaker, place the beaker on a pH meter, and adjust the pH value of the test solution to 6-7 with hydrochloric acid (3.3).
6.1.3 Filter the test solution into a 100mL volumetric flask, wash the beaker and filter paper with hot water several times, add water to the scale, and shake well. 6.1.4 Pipette 20mL of test solution into a 50mL volumetric flask, add 1 drop of dilute hydrochloric acid (3.4), add 20mL of complex ion strength adjustment solution, add water to the scale, mix well, and use for determination.
6.2 Preparation of nitrogen standard working solution
6.2.1 Pipette 0.0, 1.0, 2.5, 5.0.10.0 mL (equivalent to 0.10, 25, 50, 100 μg fluorine) of fluorine standard solution (3.7.3) and place them in 50 mL volumetric flasks respectively. Add 1 drop of dilute hydrochloric acid (3.4) and 20 mL of complex ion strength adjustment solution to each volumetric flask respectively, add water to the scale and mix.
6.2.2 Take 2.0, 4.0, 6.0, 8.0, 10.0 mL of oxygen standard solution (3.7.2) (equivalent to 200, 400, 600, 800, 10004 g of fluorine) and place them in 50 mL volumetric flasks respectively. Add 1 drop of dilute hydrochloric acid (3.4) and 20 mL of complex ion strength adjustment solution to each volumetric flask. Add water to the scale and mix.
6.2.3 Prepare blank solution in the same way as the test solution. 6.3 Determination
6.3.1 Connect the oxygen electrode and the gamma-ray electrode to the negative and positive terminals of the measuring instrument, insert the electrodes into a 50 mL beaker filled with water, preheat the instrument for 1 hour, read the equilibrium potential value on the magnetic stirrer, and after equilibrium, the standard solution and test solution can be measured. 6.3.2 Determine the equilibrium potential of the fluorine standard working solution from low to high concentration. With the electrode potential as the ordinate and the oxygen ion concentration as the abscissa, draw the standard front on the semi-logarithmic coordinate. 6.3.3 Determine the equilibrium potential of the test solution and the blank solution in the same way, and calculate the fluorine content of the test solution from the standard curve. 7 Determination results
7.1 Calculation formula
F=(C,-C)V.
Where: C,--fluorine content of the test solution obtained from the standard curve, ug; C.--oxygen content of the blank wave obtained from the standard curve, ug; V.--total volume of the test solution, mL;
V.--volume of the test solution, mL;
m-weight of the sample, g.
7.2 Result expression
Take two parallel samples for each sample for determination, and the difference between the two parallel results shall not be greater than the allowable difference listed in Table 1. If the parallel results exceed the allowable difference, re-sample and repeat. 2
Test report
Rat content
50~100
Indicate the test of this standard:
Material name, brand, specification, manufacturer; Test name, sample number, number:
Commissioning unit;
Test results;
Testing unit, test date, test personnel. Additional remarks:
JB/T 7758. 1 95
This standard is proposed and managed by the Hefei General Machinery Research Institute of the Ministry of Machinery Industry, and serves as a model.
This standard is drafted by the Zigong Mechanical Carbon Products Research Institute of Dongxin Electric Carbon Co., Ltd. The main authors of this standard are Dai Yingchi and Yu Bo. %
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