YB/T 6261-2024 in English
VALIDDetermination of Nitrogen Content in Carbon Additive Formaldehyde Method
- Issued on:2024-10-24
- Implemented on:2025-05-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
$184.00
| Standard No: | YB/T 6261-2024 |
| Document status: | VALID |
| Title in English: | Determination of Nitrogen Content in Carbon Additive Formaldehyde Method |
| Title in Chinese: | 增碳剂 氮含量的测定 甲醛法 |
| Language: | English |
| File Format: | Electronic (PDF) |
| Delivery: | Via email within 1~3 business days |
| Issued on: | 2024-10-24 |
| Implemented on: | 2025-05-01 |
| ICS Classification: | 29.050-Conducting materials |
| Chinese Classification: | Q52-Carbon material |
| Professional Classification: | YB-Metallurgy |
| Related Keywords: | formaldehyde method
carbon additive formaldehyde method introduction technical background neutral formaldehyde solution formaldehyde solution nitrogen content |
Introduction
Technical background of the standard
As an important testing specification for the ferrous metallurgical industry, this standard is formulated under the framework of GB/T 1.1-2020 to control the nitrogen content in the production process of recarburizers. Compared with the traditional Kjeldahl method, the formaldehyde method has the advantages of efficient pre-treatment of microwave digestion instrument and strong formaldehyde reaction specificity, and the detection limit can reach 0.20%.
Detailed explanation of the method principle
| Reaction stage | Chemical reaction formula | Critical control point |
|---|---|---|
| Digestion and transformation | N(organic matter)+HNO3→NH4+ | Microwave power1600W, 180℃ insulation for 45min |
| Formaldehyde reaction | 4NH4++6HCHO→(CH2)6N4H++3H++6H2O | Neutral formaldehyde solution must be neutralized before use |
| Titration determination | H++NaOH→Na++H2O | Phenolphthalein endpoint control does not fade for 30s |
Key reagents and instruments
Key points for reagent configuration
Sodium hydroxide standard solution needs to be calibrated with potassium hydrogen phthalate, and the configuration requirements for different concentrations are:
- 0.0050mol/L: dilute 0.27mL of saturated NaOH to 1L
- 0.010mol/L: dilute 0.54mL of saturated NaOH to 1L
Neutral formaldehyde solution (25%) needs to be pre-neutralized with neutral red-methylene blue indicator, and the mixed indicator solution is valid for only 7 days.
Instrument operation specifications
Microwave digestion instrument must be equipped with a polytetrafluoroethylene digestion tank, program settings:
- Power gradient increased to 1600W
- Pressure control 800psi
- Three-stage temperature control (30min heating → 180℃ constant temperature → natural cooling)
Detection process optimization suggestions
| Operation links | Common problems | Solutions |
|---|---|---|
| Sample preparation | Particle size＞0.2mm | Use air flow mill for secondary treatment |
| Digestion process | Acid mist leakage | Check the integrity of the digestion tank seal ring |
| End point determination | Color reversion phenomenon | Control environmental CO2 concentration |
Quality control requirements
According to Chapter 10 of the standard, the precision control equation is:
- Repeatability limit r=0.0264m+0.0173
- Reproducibility limit R=0.0436m+0.0161
Example: When the nitrogen content is 1.50%, r=0.057%, R=0.081%. The laboratory should verify with CRM standard substances regularly.
Implementation precautions
Safety protection
The experiment should be carried out in a fume hood. If hydrofluoric acid contacts the skin, it should be treated with calcium gluconate gel immediately.
Data rounding
The final result is rounded to two decimal places according to GB/T 8170. When the difference between the third measurement result and the previous two mean values is ≤1.2r, the average of the three measurements is taken.
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