GB/T 17776-2016 in English

Determination principle:Use magnesium nitrate to fix the sulfur in the feed sample and oxidize it completely. Under acidic conditions, use barium chloride to precipitate sulfate ions into barium sulfate. After filtering, washing and burning, weigh it in the form of barium sulfate to calculate the sulfur content.

Analysis of determination steps

1. Sample weighing:Weigh $2\mathrm{g}{\sim}5\mathrm{g}$ sample (accurate to $0.0001\mathrm{g}$) in a $50~\mathrm{mL}$ porcelain crucible.
2. Sample treatment:Add magnesium nitrate solution, mix well, heat and carbonize until smokeless, then burn in a high-temperature furnace to remove black particles from the sample.
3. Precipitation and filtration:After cooling, add water and hydrochloric acid, boil and filter, and wash the filter residue with hot distilled water until the filtrate is about $200~\mathrm{mL}$.
4. Sulfate precipitation:Add barium chloride solution dropwise and continue to boil for $5$ minutes, let it stand overnight and filter with slow quantitative filter paper.
5. Burn and weigh:Move the precipitate and filter paper into a porcelain crucible with constant weight, burn to constant weight at $(820 \pm 20)^{\circ}\mathrm{C}$, and calculate the mass of barium sulfate.

Experimental condition control: The high temperature furnace needs to be precisely controlled at $820~\mathrm{C} \pm 20~\mathrm{C}$ to ensure complete burning process.

Reagent selection:Magnesium nitrate and barium chloride must be analytically pure reagents, and the experimental water must meet the requirements of Grade 3 water in GB/T 6682.

Safety precautions:When operating magnesium nitrate, protective equipment should be worn and laboratory safety regulations should be strictly followed, especially during the heating process, low heat should be used with caution.