For benzoic acid - Weigh accurately about 2.5 g. dissolve with the aid of genila heat,

light (365 nm) and corresponding in colour and positron to the spot in the chrornatogram obtained with solution (2) Assay; For benzoic acid - Weigh accurately about 2.5 g. dissolve with the aid of genila heat, as completely as possible, in 50 ml of a mixture of equal volumes of ellivi: (95%) and ether. previously neutralised to phenolphthalein solution and trtrate with 0.1M sodium hydroxide using phenolphihafein solution as indicator. Each mf of 0.1M sodium hydroxide, after deducting 1 ml for each 0.01381 g of C7H6O3 in the weight of the ointment taken (calculated from the result of the Assay for salicylic acid) is equivalent to 0.012219 of C7H6O2 For salicylic acid • Weigh accurately about 2..5 g, dissolve with the aid of gentle heat, as completely as possible, in 50 ml of ether, and extract with 5 quantities, each of 10 ml, of a saturated solution of sodium bicarbonate, washing each extract with the same 50 ml of ether. Combine the aqueous extracts, cautiously add hydrochloric acid until the solution Is distinctly acid to litmus paper and extract with 4 quantities, each of 25 ml. of ether, combine the extracts and evaporate the elder at a temperatura below 40° Dissolve the residue in 5 ml of 0.5M sodium hydroxide, add 50.0 ml of 0.1 M bromine and 5 ml of hydrochloric acid, shake repeatedly dunng 15 minutes and allow to stand for 15 minutes. Add 10 ml of potassium iodide solution and titrate with 0.1M sodium thiosulphate using starch solution, added towards the end of the titration, as indicator Repeat the operation without the substance being examined. The difference between the titrations represents the amount of bromine required Each ml of 0.1 M bromine is equivalent to 0.002302 g of C7H6O3 BENZOIN Benzoin is the balsamic resin obtained from Styrax benzoin Dryander or Styrax paralleloneurus Perkins, known in commerce as Sumatra Benzoin or from Styrax tonkmensis (Pierre) Craib ex Harwich, or other species of the Section Anthostyrax of The ganus Styrax. known in commerce as Siarn Benzoin (Fam. Slyraceae) Category Topical protetlant, expectorant and comforting by steam inhalation in acute laryngitis Description Unground Sumatra Benzoin -Blocks or lumps of varying size, made up of tears compacted together, wim a red dish-brown, reddish-grey or greyish-brown resinous mass, known in commerce as block benzoin.it also occurs in the form of tears with cream-coloured to yellowish surfaces, when fractured they exhibit milky-white surfaces; odour, balsamic which accentuates on digestion with boiling water Unground Siam Benzoin -Pebble-like tears of variable size and shape, compressed, yellowish-brown to rusty-brown externally, milky white on fracture, hard and brittle at ordinary temperatures but softened by heat, odour,, balsamic Storage Store in well-closed, Iighl-resistant containers in a cool place Labelling The label states whether it is Sumatra Benzom or Starn Benzoin STANDARDSBenzoin contains not less than 25.0 per cent of total balsamic acids, calculated as cinnamic acid, C9H8O2, in Sumatra Benzom and as cenzoic acid. C.H6O2. in Siam Benzoin, calculated with reference to the dried substance Identification. A To a solution in ethanol (95%) add water, the solution becomes milky and the mixture is acid to litmus paper B Heat 0.5 g in a dry test tube, it melts and- evolves white ' fumes which form a white needle-shaped crystalline subhmste.C Heat 0 5 g in a test-lube with 5 ml of potassium permanganate solution, a strong odour of benzatdehyde is obtained with Sumatra Beltzoin O; Carry out the method for thin-layer chromatography. Appendix 4 &, using kieselguhr as the coating substance and a mixture of 93 voturnes of toluene and 7 volumes of ethylacerale as the mobile phase. Apply separately to the plate 20 pi each of the following solutions Solution (1] is a 2.0% Wv solution of the substance being examined in ethanol (95%) Solutions 4).Q),(4).(5),(6) and (7) are 0.05% w/v solutions of benzoiC acid RSb Einnamic acid RS, comferyl benzoate RS. Cinnamcyl cinnamate RS, propyl cmnamute. RS and cmnamoyl benzoate RS respectively in chloroform After removal of the plate, allow it to dry in air until the odour of the solvent is no longer detectable and spray with amsaldehyde-sulphunc acid reagent Heat the plate at 110" for 5 minutes and examine under ultra-viofet light (254 nm) In the case of Sumatra Benzoin, the chromatogram obtained with solution (1) exhibrts four intense spots corresponding to spots in the chfomalograms obtained wrth solutions (3). (4), (5) and (6) In the case of Siarn Benzoin, rt exhibits intense spots corresponding to spots in the chromatograrns obtained with solutions (2), (4), (5) and (7) Dammar gum Carry out the method for thin-layer chromatography, Appendix 4.6. using aluminium oxide G as the coating substance and a mixture of 60 volumes of ether and 40 volumes of Light petroleum (boiling range 90" to 100*) as the mobile ptiase but alowtng the solvent front to ascend 10 cm above the line of application Apply to the plate 5 pi of a solution prepared by warming 0.2 g of the substance being examined with 10 ml of ethanol (90%) and centnfuging. After removal of the plate, allow it to dry in air, spray with amsaldehyde-sulphunc acid reagent and heat at 100° to 105° for 5 minutes. The chromatogram does not show any prominent spot with an RF value between 0.4 and 1.0 foreign organic matter not more than 1.0%, Appendix 3.35 Elhanel-soluble extractive. Not less than