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The sudden turbidity of the alkali cylinder upon preparation, the subsequent clarification after standing still, and the precipitation of crystals when stored, are all typical phenomena and are not caused by mistakes in the ratio or material addition operation.
The commonly used ratio for the alkali cylinder is: Sodium Hydroxide : Pure Water : Anhydrous Ethanol = 1:1:3 by mass ratio. The dissolution of sodium hydroxide is highly exothermic when dissolved in water. If ethanol is added suddenly, it will disrupt the dissolution equilibrium, and the solubility of strong alkali alcohol salts will drop sharply, causing immediate precipitation of white turbidity; when the water temperature drops and the molecules slowly intermix, the system will re-clarify. The repeated precipitation of crystals is caused by temperature fluctuations and imbalance in the ratio of alcohol and water, which leads to changes in the solubility of salts.
Correct configuration steps: First, add a certain amount of pure water, then gradually add NaOH in batches, stir until completely dissolved and let it cool naturally. After cooling, slowly pour in ethanol and stir uniformly while adding. This can be done when soaking glassware daily, avoiding storage in high-temperature environments. Rinse the used glassware with clean water to thoroughly remove the residual alkali solution and reduce the problem of repeated precipitation of crystals.
