How does the selection of aluminum sulfate solution affect its long-term storage stability?
Publish Time: 2024-12-18
In the daily operation of the laboratory, the preparation of aluminum sulfate solution seems routine, but it is actually a mystery. The choice of solvent is a key factor, which profoundly affects the stability of the solution during long-term storage.
Taking the common water solvent as an example, there is a difference between ordinary distilled water and deionized water. If ordinary distilled water is used, trace amounts of calcium, magnesium and other ionic impurities in it may undergo a slow ion exchange reaction with aluminum sulfate when the aluminum sulfate solution is stored. Calcium ions are easily combined with sulfate ions to form slightly soluble calcium sulfate precipitates. As time goes by, the precipitate gradually precipitates, which not only reduces the effective concentration of aluminum sulfate in the solution, but also may interfere with the requirements of subsequent experiments on the purity of the solution, making the solution turbid and stratified, and the stability is greatly reduced. Deionized water removes most of the metal ions, which can effectively reduce such unnecessary chemical reactions and provide a relatively more stable initial environment for aluminum sulfate solutions.
In terms of organic solvents, alcohol solvents will be considered when some experiments require special systems. For example, ethanol has the characteristics of strong volatility. If ethanol is used as a solvent to prepare aluminum sulfate solution, ethanol will continue to evaporate during storage, and the concentration of the solution will change rapidly, destroying the original ratio balance. Aluminum sulfate tends to be supersaturated due to the reduction of solvent, and then crystallizes and precipitates, which seriously affects the stability. In addition, the change in the internal pressure of the container caused by volatilization also increases the risk of solution leakage and container rupture.
The mixed solvent system is also complex. For example, the addition of acetone to a water-acetone mixed solvent changes the polarity of the solution. In this mixed polarity environment, the hydrolysis equilibrium of aluminum sulfate is disturbed, the tendency of aluminum ions to hydrolyze to form aluminum hydroxide colloids is intensified, and the colloid precipitation aggregates and sinks, making the upper and lower components of the solution uneven, and the stability plummets. In addition, the volatilization rates of different components of the mixed solvent vary greatly, further exacerbating the concentration fluctuations and composition changes, making it difficult to store the solution for a long time.
It can be seen that in order to ensure the long-term storage stability of aluminum sulfate solution, the type of solvent needs to be carefully weighed during preparation. According to the purpose of the experiment, storage time and environmental conditions, it is necessary to accurately select solvents with low impurity content, suitable volatility characteristics, stable chemical properties and good compatibility with aluminum sulfate, firmly lock the solution performance, and ensure the reliability of experimental data and safe operation.
