Sodium sulfate, also known as mirabilite, is a widely used chemical compound with diverse applications in various industries, including glass manufacturing, detergent production, and water treatment. Understanding the solubility characteristics of sodium sulfate is crucial for its effective utilization and optimization of industrial processes. This comprehensive guide delves into the intricate details of Na2SO4 solubility, providing a wealth of technical information to aid science students and professionals.
Solubility of Sodium Sulfate in Water
The solubility of sodium sulfate in water is a crucial parameter that varies with temperature. At 20°C, the solubility of Na2SO4 in water is approximately 190 g/L [101]. As the temperature increases, the solubility also rises, reaching around 430 g/L at 100°C [101]. However, it is important to note that the solubility can decrease slightly at 20°C, with reported values ranging from 161 to 162 g/L in some cases.
The temperature-dependent solubility of sodium sulfate can be described by the following equation:
Solubility (g/L) = 0.0017 × T^2 + 0.1767 × T + 17.909
Where T is the temperature in degrees Celsius (°C).
This equation is valid within the temperature range of 0°C to 100°C and provides a reliable estimate of the solubility of Na2SO4 in water under these conditions.
Solubility in Other Solvents
In addition to water, sodium sulfate exhibits solubility in other solvents, such as glycerol. The solubility of Na2SO4 in glycerol is reported to be significantly lower than in water, with a value of approximately 50 g/L at 20°C.
On the other hand, sodium sulfate is considered insoluble in alcohol, with a negligible solubility in this solvent.
Hygroscopic Nature and Hydrate Formation
Sodium sulfate is known to be a hygroscopic compound, meaning it has the ability to absorb moisture from the surrounding environment. In moist air, Na2SO4 will readily absorb water and form hydrates, which can affect its physical properties and behavior.
The hydration of sodium sulfate can be represented by the following equation:
Na2SO4 + 10 H2O ⇌ Na2SO4·10H2O (mirabilite)
The formation of the decahydrate, Na2SO4·10H2O, known as mirabilite, is a common occurrence when sodium sulfate is exposed to humid conditions.
Density and Melting Point
The relative density of sodium sulfate is approximately 2.7 g/cm³ at 20°C and 2.671 g/cm³ at 25°C. This high density can be attributed to the compact crystal structure of the compound.
The melting point of sodium sulfate is reported to be in the range of 800-888°C, depending on the specific conditions and the presence of impurities. This high melting point results in an extremely low vapor pressure for Na2SO4, making it a relatively stable compound at standard temperature and pressure.
Octanol-Water Partition Coefficient (log Pow)
The octanol-water partition coefficient, commonly denoted as log Pow, is a measure of the distribution of a substance between the octanol and water phases. For sodium sulfate, the log Pow value is calculated to be -4.38, using a computer program.
This negative value of the log Pow indicates that sodium sulfate is highly soluble in water and has low solubility in octanol. This property is consistent with the ionic nature of the compound and its strong hydrophilic character.
Factors Affecting Solubility
The solubility of sodium sulfate can be influenced by various factors, including:
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Temperature: As mentioned earlier, the solubility of Na2SO4 increases with increasing temperature, following the relationship described by the equation.
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Pressure: The solubility of sodium sulfate is generally not significantly affected by changes in pressure, as it is a non-volatile compound.
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Presence of other substances: The presence of other ions or compounds in the solution can affect the solubility of sodium sulfate through various mechanisms, such as ion pairing, complexation, or changes in the ionic strength of the solution.
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Crystalline form: The solubility of sodium sulfate can be influenced by the specific crystalline form present, as different polymorphs may have slightly different solubility characteristics.
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Particle size: The surface area-to-volume ratio of the sodium sulfate particles can impact the dissolution rate and, consequently, the observed solubility.
It is essential to consider these factors when reporting or using solubility data for sodium sulfate, as they can significantly affect the values obtained.
Practical Applications and Considerations
The solubility characteristics of sodium sulfate have important implications in various applications, including:
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Glass manufacturing: Sodium sulfate is a common ingredient in glass formulations, where its solubility and thermal properties play a crucial role in the melting and refining processes.
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Detergent production: Sodium sulfate is used as a filler and bulking agent in many detergent formulations, and its solubility affects the performance and handling of these products.
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Water treatment: Sodium sulfate is employed in water treatment processes, such as coagulation and precipitation, where its solubility influences the efficiency of these operations.
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Pharmaceutical and medical applications: Sodium sulfate has been used in some pharmaceutical and medical applications, where its solubility characteristics are important for formulation development and drug delivery.
When working with sodium sulfate, it is essential to consider the specific conditions, such as temperature, pressure, and the presence of other substances, to accurately predict and control its solubility behavior.
Conclusion
This comprehensive guide has provided a detailed overview of the solubility characteristics of sodium sulfate (Na2SO4), also known as mirabilite. From the temperature-dependent solubility in water to the compound’s solubility in other solvents, hygroscopic nature, density, melting point, and octanol-water partition coefficient, this guide has covered a wide range of technical details relevant to science students and professionals working with this versatile chemical compound.
By understanding the factors that influence the solubility of sodium sulfate, researchers and industry professionals can optimize processes, develop effective formulations, and make informed decisions in various applications, such as glass manufacturing, detergent production, and water treatment. This comprehensive guide serves as a valuable resource for gaining a deep understanding of the solubility behavior of sodium sulfate.
References
- OECD HPV Chemical Programme. (n.d.). Sodium Sulfate. Retrieved from https://hpvchemicals.oecd.org/ui/handler.axd?id=3ac5dc59-ed2c-410c-afa7-c1608b978d7f
- Lide, D. R. (Ed.). (2005). CRC Handbook of Chemistry and Physics (86th ed.). CRC Press.
- Haynes, W. M. (Ed.). (2014). CRC Handbook of Chemistry and Physics (95th ed.). CRC Press.
- Kaye, G. W. C., & Laby, T. H. (1995). Tables of Physical and Chemical Constants (16th ed.). Longman.
- Weast, R. C. (Ed.). (1984). CRC Handbook of Chemistry and Physics (64th ed.). CRC Press.
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