Preparation of Ammonium Sulfate Saturated Solution

Introduction

Ammonium Sulfate is commonly used for reagent for protein precipitation (ammonium sulfate precipitation) and fractionation as it enhances hydrophobic interactions. Ammonium sulfate is an inorganic sulfate salt obtained by reaction of sulfuric acid with two equivalents of ammonia. A high-melting (decomposes above 280℃) white solid which is very soluble in water (70.6 g/100 g water at 0℃; 103.8 g/100 g water at 100℃). Ammonium sulfate is used as a fertilizer for alkaline soils as well. Ammonium sulfate is a white odorless solid.

Properties of Ammonium Sulfate

• Formula: (NH₄)₂SO₄
• Synonyms: Ammonium sulphate, Mascagnite, Diammonium sulphate, sulphate of ammonia, dolamin
• Molar mass: 132.14 g/mol
• Solubility: freely soluble in water, insoluble in ethanol, acetone
• Exact mass: 132.02047791 g/mol
• Monoisotopic mass: 132.02047791 g/mol
• pH = 5.5 (0.1 M aqueous solution)

Components Required in the Preparation

Components	Amount
Ammonium sulfate	781 G (5.759 M)
DI water	to 1 L

Preparation of Saturated Ammonium Sulfate Solution

Here are the steps involved in preparation of the saturated ammonium sulfate solution.

• Prepare 800 mL of distilled water in a suitable container.
• Add 761 g of ammonium sulfate to the solution.
• Add distilled water until the volume is 1 L.
• Dissolve with stirring and gentle heating. Cool to room temperature and adjust the pH to 7 (with NH4OH or an acid such as HCl). If excess is to be stored, sterilize the solution by filtering through a 0.2 micron filter and store at 4 degrees-C.

References

• 1. https://pubchem.ncbi.nlm.nih.gov/compound/Ammonium-Sulfate