Benzoic Acid Solution

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.

4.75  to 5.25% w/v.

A.  To 5  ml add 30  ml of 1m sulphuric 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.

1.045  to 1.055  g, Appendix V G.

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.

The label states (1) the date after which the solution is not intended to be used; (2) the conditions under which it should be stored.