Concentrated sulfuric acid above 98.5 will precipitate
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The chlorine drying process uses concentrated sulfuric acid to dry chlorine gas; the concentration of this acid in use is ≥98%, and it typically measures around 98.9% upon arrival at the plant. White precipitates can be observed in the acid sample – is this due to the high concentration of sulfuric acid causing certain compounds to precipitate?
No, it’s just that the impurities in the sulfuric acid are too high
The freezing point of 98–99% concentrated sulfuric acid is around 1–3 °C; it does not freeze at room temperature. The white suspension you mentioned is likely to be impurities such as sealing materials and debris from other pipelines and components that have mixed in during the loading of the sulfuric acid.
Phase transition crystallization of concentrated sulfuric acid and the appearance of impurities are two different things; it might be the contamination issue mentioned by the person above.
When impurities or dust particles are extremely small, they appear white; you should check whether there is any dust present in your chlorine
Concentrated sulfuric acid (H₂SO₄) is a colorless, viscous liquid at normal temperature and pressure, and its crystallization behavior is closely related to concentration and temperature. Regarding the question, \"Will concentrated sulfuric acid above 98.5% precipitate?\" ”Below is a detailed analysis: 1. Crystallization properties of concentrated sulfuric acid. Concentration and freezing point: The freezing point of pure sulfuric acid (100%) is 10.4°C, while the concentration of sulfuric acid commonly used in industry is 98.3% (an azeotropic mixture), and its freezing point is approximately -20°C. When the concentration is higher than 98.5% (such as 99% or 100%), the freezing point increases significantly. For example, the freezing point of 99% H₂SO₄ is approximately 1.5°C. The freezing point of 100% H₂SO₄ is 10.4°C. Precipitation condition: If the temperature is below the freezing point corresponding to that concentration, sulfuric acid will crystallize and precipitate (forming a solid state). 2. Practical application considerations: Storage temperature: If the storage environment is at a temperature lower than the freezing point (such as in cold winter regions), crystals may form in sulfuric acid with a concentration of over 98.5%. For example, 100% sulfuric acid freezes at temperatures below 10°C. Effect of impurities: Trace impurities (such as moisture and metal ions) may alter the freezing point, but the precipitation behavior of high-purity sulfuric acid depends primarily on concentration and temperature. 3. Industrial precautions: Anti-freezing measures: High-concentration sulfuric acids (such as fuming sulfuric acid, containing SO3) tend to solidify more easily at low temperatures; therefore, they need to be stored in a temperature-controlled environment or with anti-freezing agents added. Safety risk: When solid sulfuric acid is remelted, local overheating may cause the container to break or lead to splashing; therefore, the temperature should be increased gradually. Conclusion Sulfuric acid with a concentration of over 98.5% will precipitate crystals when the temperature is below its corresponding freezing point (for example, 99% sulfuric acid at below 1.5°C). In practical use, it is necessary to select an appropriate concentration based on the ambient temperature or take insulation measures.
It won’t happen; it’s most likely impurities from the sulfuric acid production process, such as dust. It is recommended to test the quality of the gas; if there are no issues with its quality, then it’s fine to use it. After all, drying simply makes use of the gas’s absorbency properties