Edition: BP 2025 (Ph. Eur. 11.6 update)
General Notices
| Benzoic Acid | 50 g |
| Propylene Glycol | 750 mL |
| Purified Water, freshly boiled and cooled | Sufficient to produce 1000 mL |
Extemporaneous preparation
The following directions apply.
Dissolve the Benzoic Acid in the Propylene Glycol and add sufficient Purified Water, in small quantities and with constant stirring, to produce 1000 mL.
Content of benzoic acid, C7H6O2
4.75 to 5.25% w/v.
IDENTIFICATION
A. To 5 mL add 30 mL of 1M sulfuric acid and extract the precipitated acid with three 25-mL quantities of petroleum spirit (boiling range, 40° to 60°). Wash the combined extracts with three 25-mL quantities of water, filter through absorbent cotton and evaporate to dryness. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of benzoic acid (RS 025).
B. Melting point of the residue obtained in test A, about 121°, Appendix V A.
TESTS
Weight per mL
1.045 to 1.055 g, Appendix V G.
ASSAY
To 10 mL add 20 mL of ethanol (96%) previously neutralised to phenolphthalein solution R1 and titrate with 0.1M sodium hydroxide VS using phenolphthalein solution R1 as indicator. Each mL of 0.1M sodium hydroxide VS is equivalent to 12.21 mg of C7H6O2
.
