About glauber's salt and ammonium sulfate

Here is a note on glauber's salt and ammonium sulfate, which are sometimes found in wastewater from chemical plants.

Sodium sulfate is the IUPAC name , and sodium sulfate decahydrate is called sodium glauber. A solution of sodium hydroxide neutralized with sulfuric acid yields crystals of sodium sulfate decahydrate.

NaOH + H2SO4 -> Na2SO4 + 2H2O

The solubility curve of sodium sulfate is bent at 32.4°C as shown in the figure below*1, and this point is called the transition point.

Solubility of sodium sulfate (water)

*1) The solubility of sodium sulfate increases with increasing temperature up to 32.4℃, but decreases above 32.4℃. This is because the solubility of the hydrate is -56.0 kJ (endothermic), while the heat of dissolution of the anhydride is +2.34 kJ (exothermic).

Ammonium sulfate is the IUPAC name, a compound with the chemical formula (NH4)2SO4. It is a colorless crystal, easily soluble in water.

2NH3 + 2H2O + H2SO4 -> (NH4)2SO4 + 2H2O

Graph source: Science university entrance exam, new research on chemistry I and II, by Yoshihiro Urabe, 2005, 6th edition, p132

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