0.1 N Lithium Methoxide in Toluene 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)
CH3OLi, 37.97 3.798 g in 1000 mL
Dissolve 700 mg of freshly cut lithium metal in 150 mL of methanol, cooling the flask during addition of the metal. When reaction is complete, add 850 mL of toluene. If cloudiness or precipitation occurs, add sufficient methanol to clarify the solution. Store preferably in the reservoir of an automatic delivery buret suitably protected from carbon dioxide and moisture.
Standardization: Accurately weigh about 400 mg of primary standard benzoic acid, and dissolve in 80 mL of dimethylformamide in a flask. Add 3 drops of a 1-in-100 solution of thymol blue in dimethylformamide, and titrate with the lithium methoxide solution to a blue endpoint. Correct for the volume of the lithium methoxide solution consumed by 80 mL of the dimethylformamide. Each 12.21 mg of benzoic acid is equivalent to 1 mL of 0.1 N lithium methoxide.
[Note—Restandardize the solution frequently.]
N= mg benzoic acid/ (122.12 × mL lithium methoxide (corrected for the blank))
[Note—If this volumetric solution is used in a qualitative application such as pH adjustment, dissolution medium, or diluent, its standardization
is not required.]
