0.1 N Ferrous Ammonium Sulfate VS
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
(USP 1-May-2021)
Dissolve 40 g of ferrous ammonium sulfate in a previously cooled mixture of 40 mL of sulfuric acid and 200 mL of water, dilute with water to 1000 mL, and mix.
Standardization (carried out on the day of use)
See Volumetric Solutions, 1. Introduction.
See Titrimetry (541).
Standardize by one of the following procedures. [NOTE-Other standardization procedures may be used. See Volumetric Solutions, 2. Preparation and Standardization, 2.3 Standardization.]
Standardization with visual endpoint: (USP 1-May-2021) Accurately measure 25-30 mL of the solution into a flask, add 2 drops of orthophenanthroline TS, and titrate with 0.1 N ceric sulfate VS until the red color is changed to pale blue.
N = (mL CeIV x N CeIV)/(mL Fell Solution)
Standardization with potentiometric endpoint: Accurately measure 10-15 mL of the solution into a flask, add about 50 mL of water and titrate with 0.1 N ceric sulfate VS potentiometrically using a combined platinum (Pt) electrode.
N = (mL CeIV x N CeIV)/(mL Fell Solution) (USP 1-May-2021)
[NOTE-If this volumetric solution is used in a qualitative application such as pH adjustment, dissolution medium, or diluent, its standardization is not required.]
