GB/T 5195.5-2017 in English

1. Background of standard formulation and analysis of technological evolution

Since its first release in 1985, the GB/T 5195 series of standards have been continuously revised to adapt to technological progress and industry needs. This part, as the fifth part, specifically regulates the determination method of total sulfur content in fluorite.

2. Interpretation of the core content of the standard

Scope of application

This standard is applicable to the determination of total sulfur content in fluorite, with a mass fraction between 0.010% and 1.00%. This method uses tube furnace combustion technology to convert sulfur into sulfur dioxide, and quantitative analysis is performed by potassium iodate titration.

Reagents and Materials

The main reagents used in the experiment include tungsten trioxide, hydrochloric acid, potassium iodide solution, etc. All reagents must meet the analytical purity requirements to ensure the accuracy of the test results. Special attention: the sulfur content of the flux tungsten trioxide used must be less than 0.001% to avoid interference with the measurement results.

Instruments and Devices

Key equipment includes:

• Tube furnace: used for high-temperature combustion, it must be able to maintain a temperature of 1200℃±25℃.
• Nitrogen generator: provides high-purity (more than 99.5%) nitrogen to ensure that there is no oxygen interference in the reaction environment.
• Potassium iodate standard titration solution: concentration is 0.006237 mol/L.

Analysis steps

The steps include sample weighing, high temperature combustion, gas absorption and titration. The specific process is as follows:

1. Mix the sample with tungsten trioxide and place it in a porcelain boat.
2. Combust at 1200℃ in a nitrogen stream to convert sulfur into SO₂.
3. SO₂ is absorbed by the acidic potassium iodide-starch solution.
4. Titrate to the endpoint with potassium iodate standard titration solution and record the consumed volume.

3. Implementation suggestions

Laboratory conditions requirements

• Ensure the calibration and maintenance of the instrument: Regularly check the temperature control accuracy of the tube furnace to ensure its stability.
• Reagent preparation: Strictly follow the preparation method in the standard, especially the potassium iodate standard titration solution.
• Environmental requirements: The laboratory must have good ventilation facilities to avoid the accumulation of harmful gases.

Operational precautions

1. Sulfide and sulfate may affect the test results. It is recommended to treat the sample before analysis to eliminate interference factors. 2. The flow rate must be strictly controlled during the titration process to ensure that SO₂ is fully absorbed.

Data recording and processing

Calculate the sulfur content according to the standard formula, and the allowable difference is determined according to the mass fraction of sulfur. For the average value of independent measurement results, it is necessary to comply with the rounding rules of GB/T8170 and retain three decimal places.