GB/T 39719-2020 in English
VALIDField and concentrated natural rubber latices—Determination of magnesium content—Cyanide-free titrimetric method
- Issued on:2020-12-14
- Implemented on:2021-07-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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《GB/T 39719-2020新鲜和浓缩天然胶乳 镁含量的测定 滴定法（无氰法）》由TC35（全国橡胶与橡胶制品标准化技术委员会）归口，TC35SC8（全国橡胶与橡胶制品标准化技术委员会天然橡胶分会）执行，主管部门为中国石油和化学工业联合会。
Introduction
Interpretation of the core content of the standard
This standard specifies the method for determining the magnesium content in fresh natural latex and concentrated natural latex by cyanide-free titration. The technical equivalent adopts the ISO17403:2014 international standard and makes adaptive modifications based on China's national conditions.
Key Technical Points
| Test Items | Method A (Fresh Latex) | Method B (Concentrated Latex) |
|---|---|---|
| Sample Amount | About 2.0g | About 10.0g |
| Key Reagents | EDTA Solution (0.005mol/L) | Acetic Acid Coagulant (25%) |
| Titration Endpoint | Red→Pure Blue (Chrome Black T Indicator) | |
| Result presentation | Latex meter or total solid content meter | Total solid content meter |
Key points for standard implementation
Instrument selection specifications
burettes (5/10/50mL) that comply with GB/T12805 and pipette that comply with GB/T12808 must be used, and the pH meter must have an accuracy of 0.1 unit. Newly added 100mL/1000mL volumetric flask specification requirements.
Reagent improvement instructions
- Specify EDTA as Disodium EDTA, and add a heating dissolution step
- When preparing the masking agent solution, ensure that the NaHS content is ≥1.68g/L
- The pH value of the buffer solution is strictly controlled in the range of 10.0-10.5
Precision control
According to the data in Appendix A:
- When the fresh latex magnesium content is 0.020%, the repeatability r=0.004%
- When the concentrated latex magnesium content is 0.0042%, the reproducibility R=0.002%
If the test result difference exceeds the above range, resampling is required.
Comparison of Standard Evolution
Main improvements compared to ISO17403:2014:
- Added acetic acid reagent and instrument instructions
- Optimized the preparation method of EDTA solution
- Supplemented the precision chapter (Chapter 8)
- Clarified the source of each parameter in the calculation formula
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