Dissolve about 0.1 g m 10 ml of ethanol (95%). add 2 ml of a 2.0% w/v solution of sodium tetraboiate and a few crystals

water-bath ai 30° for TO minutes and allow to cool; a blue colour is produced.D Dissolve about 0.1 g m 10 ml of ethanol (95%). add 2 ml of a 2.0% w/v solution of sodium tetraboiate and a few crystals of 2.6-dicHoroquinone-4-chlorimide; noi more man a faint blue colour is produced (distinction from bulylaied hydroxyamsale).E Dissolve a few crystals in 10 ml of ethanol (95%). add 0.5 ml of a 0.2% w/v solution or potassium ferncyanide and Q 5 ml of a 0.5% w/v solulion of feint ammonium sulphate in 0.5M sulphuric acid, a green to blue colour is produced Freezing point Between 69° and 70", Appendix B A.Clarity and colour of solution A 10% w/v solution in methanol is clear. Appendix 61. and not more intensely coloured than reference solution YS5 or BY55. Appendix 62 Related substances Carry out the method for thin-layer chromalagraphy, Appendix 4 B. using silica gel G as the coaling substance and dichlorcrnethane as the mobile phase Apply separately lo the plate 10 ul of each oliwo solutions of the substance being examined in methancl containing (1) 2.0% and (2) 0.01 % w/v After removal of the plate, allow il dry in air and spray with a freshly prepared mixture of 70 volumes of water. 20 volumes of feme chloride solution and 10 volumes of potassium ferncyanide solution Any secondary spot m the chromatogram obtained with solution (1) is not more intanse than the spot in the chromatogram oblamed with solution (2J Sulphated ash Not more than 0.1 %, Appendix 3 22 CAFFEIWEC8 H10 O2 Mol Wt 194.19 (anhydrous) C8 H10 N4.H2 O Mol Wl 21221 (monohydrate) Caffeine is 3,7-dihydn- 1,3,7-trimethyl-IB-purine-2.G-diane or rts monohydrate Category Central nervous system stimulant Dose 300 lo 600 mg Descnption: Sjlky white crystals or white glistening needles or white crystalline powder, odourless, sublimes readily Solubility Freely soluble in chloroform and in boiling water, spanngly soluble in water and in ethanol (95%). slightly soluble in ether Storage Store in tightly-closed containers.Labelling: The label stales whether it is anhydrous or monohydrate STANDARDSCaffeme contains not less Ehan 38 5 per cent and not more than 101 5 per cent of C8 H10 N4 O2 . calculated with reference to the dried substance Identification Test A may Be omilled if tests B. C. D and E are carried out Tests B, C and D may be omitted if tests A and E are carried out A. The infra-red absorption spectrum, Appendix 5.4. of the substance being examined after drying at 100* for 1 hour is concordant with the reference spectrum of caffeine or with the spectrum obtained from caffeine RS B. To 10 mg in a porcelam dish, add 1 ml of hydrochloric acid and 0.1 g of potassium chlorals and evaporate to dry ness on a water-baln. Expose the residue to the vapours of dilute ammonia solution, a purple colour is produced which disappears on addition of a solution of a fined alkali C: To 9 saturated solution add a few drops of tannic acid solution, a white precipitate is produced which is soluble in excess of the reagent.D: To 5