Ammonium Sulfate
(NH4)2SO4 132.14

Ammonium sulfate [7783-20-2].
»Ammonium Sulfate contains not less than 99.0percent and not more than 100.5percent of (NH4)2SO4.
Packaging and storage— Preserve in well-closed containers.Store at room temperature,and avoid excessive heat and freezing.Protect from moisture.
Identification— Asolution (1in 20)responds to the tests for Ammonium á191ñand for Sulfate á191ñ.
Microbial limits á61ñ— The total aerobic microbial count does not exceed 1000cfu per g and the total combined molds and yeasts count does not exceed 1000cfu per g.
pHá791ñ: between 5.0and 6.0,in a solution (1in 20).
Residue on ignition— Not more than 0.005%,determined on a 20-g sample.
Limit of insoluble matter— Transfer 20g to a covered beaker,and dissolve in 200mLof water.Heat to boiling,and warm on a steam bath for 1hour.Filter the hot solution through a tared sintered-glass crucible of medium porosity (10–15µm).Wash the beaker and the filter with hot water,dry the crucible at 105,cool in a desiccator,and weigh:not more than 1mg of insoluble matter is found (0.005%).
Limit of phosphate—
Standard Phosphate Solution,Phosphate Reagent A,andPhosphate Reagent B— Prepare as directed for Phosphate in Reagentsin General Tests for Reagentsunder Reagents,Indicators,and Solutions.
Procedure— [NOTE—The tests with the specimen and the control are made preferably in matched color-comparison tubes.]Dissolve 4.0g of Ammonium Sulfate in 25mLof 0.5Nsulfuric acid,add 1mLeach of Phosphate Reagents Aand B,mix,and allow to stand at room temperature for 2hours.Any blue color should not exceed that produced in a control made with 2.0mLof the Standard Phosphate Solutionand the same quantities of the same reagents as in the test with the specimen:not more than 5µg of phosphate per g is found.
Limit of chloride—
Standard chloride solution— Transfer 165mg of sodium chloride to a 100-mLvolumetric flask,and dissolve in and dilute with water to volume.Transfer 10.0mLof this solution to a 1000-mLvolumetric flask,and dilute with water to volume to obtain a solution having a concentration of 10µg of chloride per mL.
Procedure— Proceed as directed in the test for Chloride á221ñ.A2-g portion shows no more chloride than corresponds to 1.0mLof Standard chloride solution:not more than 5µg of chloride per g is found.
Limit of nitrate—
Standard Nitrate Solution andBrucine Sulfate Solution— Prepare as directed for Nitrate in Reagentsin General Tests for Reagentsunder Reagents,Indicators,and Solutions.
Test solution— Dissolve 1.0g in 3mLof water by heating in a boiling water bath,and add Brucine Sulfate Solutionto make 50mL.
Control solution— To 1.0mLof Standard Nitrate Solution,add 1.0g of ammonium nitrate,and then add Brucine Sulfate Solutionto make 50mL.
Blank solution— Use 50mLof Brucine Sulfate Solution.
Procedure— Heat the Test solution,Control solution,and Blank solutionin a boiling water bath for 15minutes with periodic gentle swirling,then cool rapidly in an ice bath to room temperature.Adjust a suitable spectrophotometer to zero absorbance at 410nm with the Blank solution.Determine the absorbance of the Test solution,note the result,and adjust the instrument to zero absorbance with the Test solution.Determine the absorbance of the Control solution.The absorbance reading for the Test solutiondoes not exceed that for the Control Solution:not more than 0.001%is found.
Limit of iron á241ñ— Dissolve 2.0g in 40mLof water,add 2mLof hydrochloric acid,and mix:not more than 5µg of iron per g is found.
Assay— Transfer about 2.5g of Ammonium Sulfate,accurately weighed,into a 500-mLeoncal flask,and dissolve in 50mLof water.Add 50.0mLof 1Nsodium hydroxide VS,place a filter funnel loosely in the neck of the flask,and boil until ammonia is expelled (about 10to 15minutes)as determined with litmus paper.Cool,add 0.15mLof thymol blue TS,and titrate the excess sodium hydroxide with 1Nsulfuric acid VS.Perform a blank determination (see Residual TitrationsunderTitrimetry á541ñ).Each mLof 1Nsodium hydroxide is equivalent to 66.07mg of (NH4)2SO4.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 2957
Pharmacopeial Forum:Volume No.30(3)Page 966
Phone Number:1-301-816-8251