A saturated sodium sulfate solution is one in which the maximum amount of sodium sulfate is dissolved in water at a given temperature. Creating such a solution based on the provided reference involves processing a specific type of starting material: a sodium sulfate brine.
Method Based on the Conventional Process
According to the conventional process described, making a saturated sodium sulfate solution is achieved as part of a larger operation focused on producing solid sodium sulfate crystals.
Here's how it's done, based on the reference:
- Starting Material: The process begins with a brine containing sodium sulfate. This brine is typically extracted from underground sources.
- Handling the Brine: The extracted brine is then stored in a reservoir.
- Processing for Saturation & Crystallization: From the reservoir, the brine is transferred to a crystallizer.
- Achieving Saturation via Cooling: Within the crystallizer, the key step for reaching saturation and beyond is cooling. The reference states that "by cooling, crystals are produced".
This indicates that the brine, which is already a concentrated solution, becomes saturated when its temperature is lowered to the point where it can no longer hold all the dissolved sodium sulfate. As cooling continues past the saturation point (into supersaturation), solid sodium sulfate crystals begin to form. Therefore, in this context, you make the solution saturated by cooling the initial concentrated brine.
The Role of Cooling in Saturation
For substances like sodium sulfate decahydrate (Na₂SO₄·10H₂O), solubility significantly decreases as the temperature drops below approximately 32.3°C. By cooling the sodium sulfate brine, you reduce the amount of sodium sulfate that can remain dissolved. This reduction in solubility forces the excess dissolved sodium sulfate out of the solution, first reaching the saturation point, and then forming solid crystals.
The reference explicitly mentions the formation of crystals "in the form of a fine powder of sodium sulfate hydrated with ten [water molecules]", referring to the decahydrate form. This type of crystallization due to cooling is a direct result of achieving and surpassing the saturation limit of the solution at lower temperatures.
In summary, based on the provided reference, making a saturated sodium sulfate solution is achieved by taking a sodium sulfate brine and cooling it in a crystallizer until solid crystals begin to form. This point of crystal formation signifies that the solution has become saturated (and is likely supersaturated).
