0.5 N Sodium Hydroxide 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)
Transfer 500 mL of 1 N sodium hydroxide VS to a 1000-mL volumetric flask. Dilute with carbon dioxide-free water to volume.
1 Standardization
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: Accurately weigh about 1.25 g of potassium biphthalate, previously crushed lightly and dried at 120° for 2 h, and dissolve in 75 mL of carbon dioxide-free water. Add 2 drops of phenolphthalein TS, and titrate with the sodium hydroxide solution to the production of a permanent pink color.
N= [g KHC8H4O4 x (Assay/100)] / (0.20422 x mL NaOH solution)
where Assay is the content/potency of potassium biphthalate.
Standardization with potentiometric endpoint: Accurately weigh about 1.25 g of potassium biphthalate, previously crushed lightly and dried at 120° for 2 h, and dissolve in 75 mL of carbon dioxide-free water. Titrate potentiometrically with the sodium hydroxide solution using a combined pH electrode.
N= [g KHC8H4O4 x (Assay/100)] / (0.20422 x mL NaOH solution)
where Assay is the content/potency of potassium biphthalate (USP 1-Dec-2020)
[NOTE-If this volumetric solution is used in a qualitative application such as pH adjustment, dissolution medium, or diluent, its standardization is not required.]
