The maximum concentration of Hydrochloric Acid (HCl) depends on whether you are referring to the standard, readily available grade or the absolute chemically possible limit.
Based on the provided reference, the common concentrated grade of hydrochloric acid is produced in solutions up to 38% HCl.
Higher Possible Concentrations
While 38% is the standard for concentrated HCl, higher concentrations are chemically possible. According to the reference, concentrations up to just over 40% can theoretically be achieved.
Practical Challenges at High Concentrations
However, achieving and maintaining concentrations above the standard 38% presents significant practical difficulties. The reference specifically notes that at concentrations approaching and exceeding 40%:
- The evaporation rate becomes very high.
- Storage and handling require extra precautions, such as pressurization and cooling, to prevent the HCl gas from escaping the solution.
These challenges make concentrations above 38% less common and much more difficult to work with outside of specialized laboratory or industrial conditions.
In summary:
- Standard Concentrated Grade: Up to 38% HCl (most common maximum).
- Chemically Possible: Up to just over 40% HCl (requires special handling).
Therefore, while concentrations just over 40% are possible, 38% is widely considered the maximum for standard, easily handled concentrated hydrochloric acid.
