GB/T 3521-2008 English PDF (GBT3521-2008)

This Standard specifies the analysis methods of graphite products for moisture, volatile content, ash, fixed carbon content, sulfur content, and acid-soluble iron content. This Standard applies to natural graphite products.

GB/T 3521-2008
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.080
Q 51
Replacing GB/T 3521-1995
Method for chemical analysis of graphite
ISSUED ON: AUGUST 20, 2008
IMPLEMENTED ON: APRIL 01, 2009
Issued by: General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 General provisions ... 5
4 Test method ... 6
5 Allowable difference ... 17
Method for chemical analysis of graphite
1 Scope
This Standard specifies the analysis methods of graphite products for moisture, volatile content, ash, fixed carbon content, sulfur content, and acid-soluble iron content.
This Standard applies to natural graphite products.
2 Normative references
The terms in the following documents become the terms of this Standard by reference to this Standard. For dated references, all subsequent amendments (not including errata content) or revisions do not apply to this standard. However, parties to agreements that are based on this Standard are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest edition applies to this Standard.
GB/T 3518, Flake graphite
GB/T 3519, Amorphous graphite
3 General provisions
3.1 The samples for chemical analysis, which are obtained in accordance with the sampling methods that are specified in GB/T 3518 and GB/T 3519, shall be packed in plastic bags or ground-mouth bottles; the sample size shall not be less than 50 g.
3.2 Except for the determination of moisture, all other analysis items shall be analyzed after the sample is dried to constant weight at 105 °C ~ 110 °C. 3.3 The weighing of high, medium and low carbon samples shall be accurate to 0.1 mg. When constant weight is required, the difference between the two times of weighing shall not be greater than 0.3 mg. The weighing of high-purity graphite samples shall be accurate to 0.02 mg; the constant weight of the difference between two times of weighing shall not be greater than 0.05 mg. 3.4 For each analysis item, the parallel determination must be performed. For the analysis of sulfur, a blank test shall be performed.
3.5 The calculation results of high-purity graphite are expressed to three decimal places; the calculation results of the remaining items are expressed to two decimal places.
3.6 For the water that is used in this method, unless otherwise stated, only use confirmed distilled water or deionized water or water of considerable purity in the analysis.
3.7 The concentration of the solution is the molar concentration or the mass of solute in 1 L of solution (g/L). For example, (1 + 1), (1 + 2), (m + n) refer to the ratio of the volume of solute to the volume of water. Unless otherwise specified, the used solutions are all aqueous solutions.
3.8 Unless otherwise specified, in the analysis, only use the reagents that are confirmed as analytical reagents or guaranteed reagents; for the reagents that are used for calibration, only use the reagents that are confirmed as primary reagents, or spectrally pure, high-purity reagents. Unless otherwise stated, for acids and ammonia that are used in the analysis, only use confirmed
concentrated acids or alkalis.
4 Test method
4.1 Moisture determination method
4.1.1 Method summary
Dry the sample at 105 °C ~ 110 °C, to volatilize the adhered water; calculate the percentage content of adhered water according to the volatile content. 4.1.2 Instruments
4.1.2.1 Oven or other instruments of equivalent performance: the working temperature is 105 °C ~ 110 °C.
4.1.2.2 Balance: the sensitivity is 0.1 mg.
4.1.3 Analysis procedures
Accurately weigh 1 g ~ 2 g of undried samples, to the nearest 0.1 mg. Put it into a grinding-mouth weighing bottle that has been dried to a constant weight; put it in an oven at 105 °C ~ 110 °C. Open the lid; bake for 1 h ~ 2 h; take out the weighing bottle; cover it; put it in a desiccator to cool to room temperature; weigh. Put it into the oven to bake for 30 minutes; take it out; cool; weigh. Repeat this process until constant weight. It is subject to the last data. 4.1.4 Result calculation
4.3.2.3 Pyrolysis furnace: a square tube furnace that is equipped with a gas system (see Figure 1), or a box high-temperature furnace.
4.3.2.4 Sample boat: the quartz boat is used for the square tube furnace; the square porcelain boat is used for the box high-temperature furnace; the loading capacity is 0.5 g ~ 3 g.
4.3.3 Analysis procedures
Accurately weigh 0.3 g ~ 1 g (for high-purity graphite, weigh 1 g ~ 2 g) of dried sample, to the nearest 0.1 mg (to the nearest 0.01 mg for high-purity graphite); place it in a sample boat of constant weight; put the sample boat into a pyrolysis furnace that has been heated to 900 °C ~ 1 000 °C; after preheating for 1 minute, push it into the high temperature zone; introduce oxygen or air flow; burn to no black spots; take it out and place it in a desiccator after cooling; cool to room temperature; weigh. Then, put it into the pyrolysis furnace and burn for 30 min (10 min when oxygen flow is introduced); take it out; cool; weigh. Repeat this process until constant weight.
4.3.4 Result calculation
The ash is based on the mass fraction w3; the value is expressed as 10-2 or in %; it is calculated according to Formula (3):
Where:
m -- the mass of the dried sample before burning, in grams (g);
m2 -- the mass of the residue after burning, in grams (g).
4.4 Fixed carbon content determination method -- indirect carbon
determination method
4.4.1 Method summary
The indirect carbon determination method is also called the combustion method, that is, after measuring the volatile content and ash content of the sample, subtract them from the total amount, and the difference is the fixed carbon content. This method applies to graphite products whose carbon content is more than 50%.
4.4.2 Result calculation
9, 10 -- sulfur determination cup.
Figure 2 -- Sulfur determination device
4.5.4 Analysis procedures
4.5.4.1 Device tightness inspection: quickly increase the furnace temperature to 1 200 °C ~ 1 250 °C; introduce in oxygen or air; adjust the flow rate to 0.7 L/min ~ 0.8 L/min; check the device for no air leakage before testing.
4.5.4.2 Sample determination: add 2/3 volume of hydrochloric acid solution to the sulfur determination cup; add 10 mL of starch-potassium iodide solution; dropwise add potassium iodate standard solution to make the solution in the sulfur-determination cup to be light blue; use the same method to prepare a reference solution to determine the endpoint. Pass gas for 4 ~ 5 minutes; if the blue color of the solution in the sulfur-determination cup disappears, add the potassium iodate standard solution dropwise until the blue color does not disappear.
Accurately weigh 0.2 g ~ 1.0 g of the dried samples (depending on the sulfur content) to the nearest 0.1 mg. Put it into a burned porcelain boat; quickly use a sulfur-free metal hook to push the porcelain boat into the combustion tube; immediately block the nozzle; perform ventilation combustion at 1 200 °C ~ 1 250 °C. The ventilation speed should be 80 ~ 100 bubbles per minute. When the gas enters the lower part of the sulfur-determination cup to make the blue disappear, immediately add the potassium iodate standard solution dropwise; the dropping rate shall be such that the solution in the absorber keeps the original blank light blue as the limit; it’s the end until the solution's light blue remains unchanged for 1 min ~ 2 min.
4.5.4.3 Determination of correction factor: weigh 1 g of sulfur standard sample to the nearest 0.1 mg. In a porcelain boat that has been burned, proceed the followings as 4.5.4.2.
4.5.5 Result calculation
4.5.5.1 The correction factor F is calculated according to Formula (7): Where:
F -- correction factor, that is, the mass of sulfur that is equivalent to 1.00 mL of potassium iodate solution, in micrograms per milliliter (μg/mL);
m5 -- the mass of sulfur standard sample, in grams (g);
4.6.1.2.4.2 Accurately absorb 10.0 mL of solution A; put it in a 250 mL volumetric flask; use water to dilute to the mark; shake well. This solution contains 0.04 mg of iron per milliliter; this is solution B.
4.6.1.2.4.3 Drawing of working curve
Accurately measure 0.0 mL, 1.0 mL, 3.0 mL, 5.0 mL, 7.0 mL, 10.0 mL, 15.0 mL, 20.0 mL of iron standard solution B (equivalent to 0.00 mg, 0.04 mg, 0.12 mg, 0.20 mg, 0.28 mg, 0.40 mg , 0.60 mg, 0.80 mg of iron); respectively put them into 100 mL volumetric flasks; use water to dilute to about 50 mL; add 2 mL of sulfosalicylic acid solution (200 g/L); shake well. Add aqueous ammonia solution dropwise, to change the color of the solution from purple to yellow with an excess of 4 mL; use water to dilute to the mark; shake well. Let stand for 10 min. Select a 1 cm cuvette; use water as a reference; measure the absorbance of the solution at a wavelength of 420 nm. Take the iron content as the abscissa and the absorbance as the ordinate to draw the working curve.
4.6.1.2.5 Sulfosalicylic acid solution (200 g/L).
4.6.1.2.6 Ammonium thiocyanate solution (100 g/L).
4.6.1.3 Instruments
4.6.1.3.1 Balance: the sensitivity is 0.1 mg.
4.6.1.3.2 Oven or other instruments of equivalent performance: the working temperature is 105 °C ~ 110 °C.
4.6.1.3.3 Spectrophotometer or other instruments of equivalent performance. 4.6.1.4 Analysis procedures
4.6.1.4.1 Accurately weigh 0.5 g (if the iron content is less than 0.5%, 1 g ~ 3 g may be taken) of the dried sample to the nearest 0.1 mg. Put in a 150 mL beaker; use a small amount of water to wet the sample; add 25 mL (density of 1.19) of hydrochloric acid; stir, so that the sample is completely immersed in the acid; cover the watch dish; place it on the hot plate; keep it slightly boiling for 20 min; take it down; use water to wash the watch glass and the cup wall; cool slightly, use a medium-speed qualitative filter paper to filter in a 250 mL volumetric flask; use hot water to wash until there is no iron ions (use ammonium thiocyanate solution to check, there is no red); after cooling, dilute to the mark; shake well. This is the sample solution.
4.6.1.4.2 Pipette 10 mL of sample solution into a 100 mL volumetric flask; use water to dilute to about 50 mL; add 2 mL of sulfosalicylic acid solution (200 g/L); shake well. The following steps are the same as 4.6.1.2.4.3.
4.6.1.5 Result calculation
heat and boil for 3 ~ 5 minutes. Remove and cool to room temperature; transfer to a 250 mL volumetric flask; use water to dilute to the mark; mix well. 4.6.2.2.9 Ethylene diamine tetraacetic acid (EDTA) standard solution [c (EDTA) = 0.015 mol/L]
4.6.2.2.9.1 Preparation
Weigh 5.6 g of EDTA into a 1 000 mL beaker; add 600 mL of water; heat to dissolve; cool; filter; use water to dilute to 1 000 mL.
4.6.2.2.9.2 Calibration
Accurately measure 25.00 mL of calcium carbonate standard solution in a 400 mL beaker; use water to dilute to about 200 mL; add an appropriate amount of CMP mixing indicator; add potassium hydroxide solution (200 g/L) dropwise when stirring until green fluorescence appears; add an excess of 1 mL ~ 2 mL; use EDTA standard solution to titrate until the green fluorescence disappears and it shows red.
The titer T of the EDTA standard solution to ferric oxide is calculated as follows: Where:
T -- the mass of ferric oxide that is equivalent to 1.00 mL of EDTA standard solution, in milligrams (mg);
C1 -- the mass of calcium carbonate that is contained in 1.00 mL of calcium carbonate standard solution, in milligrams per milliliter (mg/mL);
V1 -- the volume of the divided calcium carbonate standard solution, in milliliters (mL);
V2 -- the volume of EDTA standard solution that is consumed during calibration, in milliliters (mL);
M1 -- molecular weight of ferric oxide;
M2 -- molecular weight of calcium carbonate.
4.6.2.3 Instruments
4.6.2.3.1 Balance: the sensitivity is 0.1 mg and 0.1 g.
4.6.2.3.2 Oven or other instruments of equivalent performance: the working temperature is 105 °C ~ 110 °C.