GB/T 3521-2023 English PDF (GBT3521-2023)

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GB/T 3521-2023: Methods for chemical analysis of graphite
GB/T 3521-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.080
CCS Q 51
Replacing GB/T 3521-2008
Methods for Chemical Analysis of Graphite
ISSUED ON: DECEMBER 28, 2023
IMPLEMENTED ON: JULY 1, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 General Stipulations ... 5
5 Determination of Moisture ... 6
6 Determination of Volatile Matter ... 7
7 Determination of Ash Content ... 10
8 Determination of Fixed Carbon Content ... 11
9 Determination of Sulfur Content ... 14
10 Determination of Acid-soluble Iron ... 21
11 Determination of Iron Content ... 26
Methods for Chemical Analysis of Graphite
WARNING: personnel using this document needs to have practical experience in
laboratory work. This document does not point out all safety, health and environmental
protection issues related to its use. It is the users’ responsibility to take appropriate safety,
health and environmental protection measures, and ensure compliance with relevant
national laws and regulations.
1 Scope
This document describes methods for the analysis of moisture, volatile matter, ash content,
fixed carbon content, sulfur content, acid-soluble iron content and iron content of graphite
products.
This document is applicable to the chemical analysis of natural graphite products.
2 Normative References
The contents of the following documents constitute indispensable clauses of this document
through the normative references in the text. In terms of references with a specified date, only
versions with a specified date are applicable to this document. In terms of references without a
specified date, the latest version (including all the modifications) is applicable to this document.
GB/T 6679 General Rules for Sampling Solid Chemical Products
GB/T 6682 Water for Analytical Laboratory Use - Specification and Test Methods
GB/T 8170 Rules of Rounding off for Numerical Values and Expression and Judgement of
Limiting Values
3 Terms and Definitions
This document does not have terms or definitions that need to be defined.
4 General Stipulations
4.1 Samples for chemical analysis obtained in accordance with the sampling method specified
in GB/T 6679 shall be packed in plastic bags or ground-mouth bottles, and the sampling size
shall be no less than 50 g.
4.2 Except for moisture determination, all other analysis items shall be analyzed after the
specimens are baked to a constant weight at 105 C ~ 110 C.
4.3 The weighing of high, medium and low carbon specimens shall be accurate to 0.1 mg, and
when constant weight is required, the difference between the two weighing values shall not be
greater than 0.3 mg. The weighing of high-purity graphite specimens shall be accurate to 0.02
mg, and when constant weight is required, the difference between the two weighing values shall
not be greater than 0.05 mg.
4.4 Each analysis item shall be determined at least twice in parallel. Take the arithmetic mean
of two parallel determination results as the analysis result.
4.5 The calculation results of high-purity graphite are rounded to four decimal places in
accordance with GB/T 8170, and the calculation results of other items are rounded to two
decimal places in accordance with GB/T 8170.
4.6 Unless otherwise stated, the water used in this Method shall not be lower than Grade-3
water specified in GB/T 6682.
4.7 The concentration of a solution is expressed as molar concentration or mass concentration.
Others, such as: (1 + 1), (1 + 2) and (m + n), etc. refer to the ratio of solute volume to water
volume. Unless otherwise specified, the solutions used are all aqueous solutions.
4.8 Unless otherwise stated, the reagents used in this Method are only those confirmed to be of
analytical purity or guaranteed purity; the reagents used for calibration are only those confirmed
to be primary reagents or of spectral purity or high purity; the acid and ammonia water used are
only confirmed concentrated acid or concentrated ammonia water.
5 Determination of Moisture
5.1 Instruments, Equipment and Materials
5.1.1 Electric drying oven: room temperature to 200 C, with a temperature control accuracy of
 2 C.
5.1.2 Analytical balance: with an accuracy not lower than 0.1 mg.
5.1.3 Ground-mouth weighing bottle: 20 mL.
5.2 Analytical Procedures
Accurately weigh-take 2 g ~ 5 g of undried specimen, accurate to 0.1 mg, and record it as m0.
Put it into a ground-mouth weighing bottle that has been dried to a constant weight, slightly
open the lid, and place it in an oven at 105 C ~ 110 C. After drying for 2 hours, take out the
ground-mouth weighing bottle and properly put on the lid of the weighing bottle. Place it in a
desiccator to cool for 30 minutes, weigh it and record it as m. Repeat this, until reaching a
constant weight.
5.3 Result Calculation
8.2.2.4 Graphite standard sample: graphite mineral composition analysis standard substance,
GBW 03118, GBW 03119, GBW 03120.
8.2.2.5 Oxygen: with a purity not less than 99.5%.
8.2.3 Instruments, equipment and materials
8.2.3.1 High-frequency infrared carbon and sulfur analyzer: carbon determination accuracy is
not less than 0.0001%.
8.2.3.2 Analytical balance: with an accuracy not lower than 0.1 mg.
8.2.3.3 Box-type resistance furnace: the maximum temperature is not lower than 1,200 C, with
a temperature control accuracy of  10 C.
8.2.3.4 Temperature controllable electric heating plate: room temperature to 300 C, with a
temperature control accuracy of  2 C.
8.2.3.5 Electric drying oven: room temperature to 300 C, with a temperature control accuracy
of  2 C.
8.2.3.6 Desiccator: equipped with color-changing silica gel.
8.2.3.7 Porcelain crucible.
8.2.4 Porcelain crucible treatment
Burn the porcelain crucible at 1,000 C for 2 hours, then, place it in a desiccator to cool and
reserve it for later use.
8.2.5 Sample treatment
Weigh-take 10.00 g (accurate to 0.1 mg) of dried specimen and place it in a porcelain crucible
that has been subjected to the burning treatment; slowly dropwise add excess hydrochloric acid
solution (1 + 1) to thoroughly acidify the sample. Then, on a temperature controllable electric
heating plate with a temperature below 150 C, slowly dry and cool it. Dropwise add water in
several times, wash the specimen, until it becomes neutral, then, move it into the box-type
resistance furnace. Raise the temperature from room temperature to 350 C, leave a gap in the
furnace door, and thoroughly burn for 2 hours. Then, take it out and cool it for later use.
8.2.6 Analytical procedures
8.2.6.1 Calibration test
Actuate the instrument and pre-heat for 30 minutes. Adjust the instrument to determine the fixed
carbon state. Turn on the oxygen; in accordance with the sample to be determined, select the
standard substance and perform system calibration, until the repeatability of the determination
results reaches the uncertainty range required by the graphite standard sample. Thus, the system
5---high-temperature porcelain tube (1,300 C);
6---tubular electric furnace (1,300 C);
7---porcelain boat;
8---burette;
9, 10---sulfur determination cups.
Figure 2 -- Sulfur Determination Device
9.1.4 Analytical procedures
9.1.4.1 Device tightness inspection: rapidly raise the furnac...