Test method of purified terephthalic acid (PTA) for industrial use—
Part 3: Determination of water content
Warning: This method does not purport to address all of the safety problems associated with its use. The user is responsible for taking proper safety and health measures and ensuring conformance to the requirements specified in relevant national regulations.
1 Scope
This part of GB/T 30921 specifies Karl Fischer volumetric method and thermogravimetry for the determination of water content in purified terephthalic acid (PTA) for industrial use.
The Karl Fischer volumetric method in this part is applicable to the determination of moisture with a content of not less than 0.010% (mass fraction) in PTA for industrial use; the thermogravimetry is applicable to the determination of moisture with a content of not less than 0.050% (mass fraction) in PTA for industrial use.
2 Normative references
The following documents are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 3723 Sampling of chemical products for industrial use—Safety in sampling
GB/T 6283 Chemical products—Determination of water—Karl·Fischer method (general method)
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 & expression and judgment of limiting values
3 Karl Fischer volumetric method (arbitration method)
3.1 Method summary
The PTA specimen is dissolved in pyridine, and the water existing in the specimen reacts quantitatively with Karl Fischer reagent (solution composed of iodine, sulfur dioxide, pyridine and methanol) with known titre. The water content in the specimen shall be calculated according to the consumed Karl Fischer reagent.
Below is the reaction formula:
Foreword i
1 Scope
2 Normative references
3 Karl Fischer volumetric method (arbitration method)
4 Thermogravimetry
5 Repeatability
6 Report
