GB/T 3521-2008 in English

《GB/T 3521-2008石墨化学分析方法》由609（中国建筑材料联合会）归口，TC406（全国非金属矿产品及制品标准化技术委员会）执行，主管部门为中国建筑材料联合会。
本标准代替GB/T 3521-1995《石墨化学分析方法》。
本标准首次发布于1983年，1995年进行了第一次修订，本次是第二次修订。
本标准规定了石墨产品水分、挥发分、灰分、固定碳含量、硫含量和酸溶铁含量的分析方法。
本标准适用于天然石墨产品。
与GB/T 3521-1995相比，本标准做了如下修改：
―――删除第1章中“石墨化学分析用试剂、仪器、分析步骤、结果计算和允许差”；
―――在第3章节中，增加了“3.6”，对试验用水作了规定；增加了“3.7”，对溶液的浓度做了具体的说明；增加了“3.8”，对所用试剂做了说明；
―――删除3.4中“铁的滴定分析应进行对照试验”；
―――挥发分的测定修改为：固定碳含量大于等于98%的石墨，将其放入已升温至400℃±10℃的热解炉中，在此温度下恒温1h；固定碳含量小于98%的石墨，将其放入已升温至950℃±10℃并已通入稳定氮气流（约200mL/min）的热解炉炉口处，关上炉门，预热1min~2min，
将托盘推入高温带，开始计时。灼烧7min后将托盘移至炉口，取出，稍冷1min~2min后，置于干燥器中冷至室温，称量；
―――删除5.2箱式高温炉法测定挥发分；
―――将硫的测定方法中的反应式修改为离子反应式；
―――酸溶铁的测定方法中将硫代硫酸钠容量法修改为乙二胺四乙酸二钠络合滴定法。

1 Scope

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

2 Normative References

The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments to (excluding corrections to), or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this standard are encouraged to study whether the latest editions of these documents are applicable. For undated references, the latest editions of the normative documents referred to apply.
GB/T 3518 Flake graphite
GB/T 3519 Amorphous graphite

3 General Requirements

3.1 The chemical analysis samples obtained according to the requirements of GB/T 3518 and GB/T 3519 shall be stored in a plastic bag or a flask with ground mouth, and the sample weight is no less than 50g.
3.2 In addition to moisture content determination, as for other analysis items, the analysis shall be conducted after the sample is baked at 105℃~110℃ to constant weight.
3.3 The accuracy of the weight of high/medium/low carbon sample shall be 0.1 mg; if constant weight is required, it shall be the difference of two times weighing which is no greater than 0.3 mg. The accuracy of the weighing of ultrapure graphite samples shall be 0.02 mg; the constant weight is the difference of two times weighing which is no greater than 0.05 mg.
3.4 Parallel determination must be carried out on all analysis items. Blank test shall be carried out for sulfur analysis.
3.5 The calculated results of ultrapure graphite shall have three digits after the decimal point, and the calculated results of other items shall have two digits after the decimal point.
3.6 Unless otherwise stated, the water used in this method is only approved distilled water, deionized water or water in equivalent purity during the analysis.
3.7 Solution concentration is molar concentration or the mass of solute contained in 1L solution (g/L). (1+1), (1+2), (m+n) refer to the ratio of solute volume to water volume. Unless otherwise stated, the adopted solution is water solution.
3.8 Unless otherwise stated, only approved analytically pure or guaranteed reagent is adopted in the analysis. Only approved reference reagent or spectroscopecally pure/ultrapure reagent is adopted for the calibrated reagent. Unless otherwise stated, as for the adopted acid and ammonia water in the analysis, only approved concentrated acid or concentrated alkali is used.

4 Test Methods

Foreword I
1 Scope
2 Normative References
3 General Requirements
4 Test Methods
5 Permissible Deviation