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Ammonium sulfate precipitation is a common method for protein purification by precipitation. As the ionic strength of a solution increases, the solubility of proteins in that solution decreases.
Ammonium iron(II) sulfate, or Mohr's salt, is the inorganic compound with the formula (NH 4) 2 SO 4 ·Fe(SO 4)·6H 2 O.Containing two different cations, Fe 2+ and NH + 4, it is classified as a double salt of ferrous sulfate and ammonium sulfate.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Ammonium sulfate is an inorganic salt with a high solubility that disassociates into ammonium (NH + 4) and sulfate (SO 2− 4) in aqueous solutions. [1] Ammonium sulfate is especially useful as a precipitant because it is highly soluble, stabilizes protein structure, has a relatively low density, is readily available, and is relatively inexpensive.
Ammonium sulfite can be prepared by the reaction of ammonia with sulfur dioxide in aqueous solution: . 2 NH 3 + SO 2 + H 2 O → (NH 4) 2 SO 3. Ammonium sulfite is produced in gas scrubbers, now obsolete, consisting of ammonium hydroxide to remove sulfur dioxide from emissions from power plants.
Ammonium persulfate is prepared by electrolysis of a cold concentrated solution of either ammonium sulfate or ammonium bisulfate in sulfuric acid at a high current density. [2] [3] The method was first described by Hugh Marshall.
It is commonly collected as a byproduct of the "acetone cyanohydrin route" to the commodity chemical methyl methacrylate. [1] It can also be obtained by hydrolysis of sulfamic acid in aqueous solution, which produces the salt in high purity: H 3 NSO 3 + H 2 O → (NH 4)HSO 4. It also arises by the thermal decomposition of ammonium sulfate:
Ammonium iron(III) sulfate, NH 4 Fe(SO 4) 2 ·12 H 2 O, or NH 4 [Fe(H 2 O) 6](SO 4) 2 ·6 H 2 O, also known as ferric ammonium sulfate (FAS) or iron alum, is a double salt in the class of alums, which consists of compounds with the general formula AB(SO 4) 2 · 12 H 2 O. [2] It has the appearance of weakly violet, octahedrical crystals.