The resulting solution complies with the limit test for chlorides, Appendix 3.10 (750

ml of saturated solution add 1. 5 ml of 0. 05M iodine, the solution remains clear. Add a few drops of dilute hydrochloric acid; a brown precipitate is formed which dissolves on neutralisation wilh sodium hydroxide solulion .E; Melts between 234° and 239°, determimed after drying at 100° for 1 hour, Appendix 8 8 Acidity or alkalinity Dissolve 0 .2 g in 10 ml of boiling water and cool. Add 0. 1 ml of bromothymol blue solution The solution is coloured green or yellow. Titrate with 0 .02M sodium hydroxide to a blue colour, not more than 0.1 ml is requiredClarity and colour of solution; A 1 0% w/v solution is clear, Appendix 6. 1, and colourless, Appendix 6 .2 Arsenic ;Mix 3 .3 g with 3 g of anhydrous sodium carbonate, add 10 ml of bromine solution and mix thoroughly Evaporate to dry ness on a water-bath, gently ignite and dissolve the cooled residue in 16 ml of bromimated hydrochloric acid and 45 ml of water. Remove the excess of bromine with 2 ml of stannous chloride solution AsT. The resulting solution complies with the limit test for arsenic, Appendix 3. 9 (3 ppm). Heavy metals Not more than 20 ppm, determined by Method A, Appendix 3. 12, on 25 ml of a solution prepared in the following manner. Mix 2.0 g with 5 ml of 0.1 M hydrochloric acid and 45 ml of water, warm gently until solution is complete and cool to room temperature. Related substances: Carry out the method for thin-layer chromatography, Appendix 4. 6, using silica gel GF254 as the coating substance and a mixture of 40 volumes of 1-butanol, 30 volumes of chloroform, 10 volumes of strong ammonia solution and 3 volumes of acetone as the mobile phase Apply separately to the plate 10 ul of each of the following solutions of the substance being examined in a mixture of 3 volumes of chloroform and 2 volumes of methanol containing (1) 2.0% w/v and (2) 0. 010% w/v. After removal of the plate, allow it to dry in air and examine under ultra-violet light [254 nm). Any secondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) Sulphated ash: Not more than 0.1 %, Appendix 3.22 Loss on drying Not more than 0.5% (for the anhydrous form) and 8.5% (for the monohydrate form), determined on 1 g by drying at 100° for 1 hour, Appendix 8.6 Assay: Weigh accurately about 0 18 g and dissolve with warming in 5 ml of anhydrous glacial acetic acid. For Caffeine Hydrate, use material previously dried at 100° to 105°. Cool, add 10 ml of acetic anhydride and 20 ml of toluene and carry out Method A for non-aqueous titration, Appendix 3.45, determining the end-point potentiometncally. Perform a blank determination and make any necessary correction Each ml 0 1 M perchloric acid is equivalent to 0.01942 g of C8H10N4O2CALAMINE Prepared Calamine Calamine is Zinc Oxide with a small proportion of ferric oxide Category: Topical protectant. Description: Fine, amorphous, impalpable, pink or reddish-brown powder. Solubility Insoluble in water. Practically completely soluble in mineral acids. Storage Store in well-closed containers. STANDARDSCalamine contains not less than 98.0 per cent and not more than 100. 5 per cent of ZnO, calculated with reference to the ignited substance. Identification A Shake 1 g with 10 ml of dilute hydrochloric acid and filter, the filtrate gives the reactions of zinc salts, Appendix 3.1.B:To 1 g add 10 ml of dilute hydrochloric acid, heat to boiling and filter To the filtrate add a few drops of ammonium thiocyanate solution, a reddish colour is produced Acid-insoluble substances: Not more than 1% w/w, determined by the following method Dissolve 1g in 25 ml of warm dilute hydrochloric acid. If any insoluble residue remains, filter, wash with water, dry to constant weight at 105°, cool and weigh Alkaline substances: Digest I g with 20 ml of warm water, filter and add 2 drops of phenolphthalem solution to the filtrate. If a red colour is produced, not more than 0 2 ml of 0 05M sulphuric acid is required to decolorise it. Water-soluble dyes: Shake 1 g with 10 ml of water and filter, the filtrate is colourless, Appendix 6.2 Ethanol-soluble dyes: Shake 1 g with 10 ml of ethanol (90%) and filter, the filtrate is colourless, Appendix 6.2 Arsenic: Dissolve 1.25 g in 15 ml of brominated hydrochloric acid AsT, add 45 ml of water and remove the excess ofbromme with a few drops of stannous chloride solution AsT The resulting solution complies with the limit test for arsenic, Appendix 3.9 (8 ppm). Lead Dissolve 2.0 g in a mixture of 20 ml of water and 5 ml of glacial acetic acid, filter and add 0 25 ml of potassium chromate solution, the solution remains clear for 5 minutes Calcium Dissolve 0.5 g in a mixture of 10 ml of water and 2 5 ml of glacial acetic acid by warming on a water-bath, if necessary and filter. To 0.5 ml of the filtrate, add 15 ml of dilute ammonia solution and 2 ml of a 2 5% w/v solution of ammonium oxalate and allow to stand for 2 minutes, the solution remains clear.Soluble barium salts: To the remainder of the filtrate obtained in the test for Calcium add 2 ml of IM sulphuric acid and allow to stand for 5 minutes, the solution remains clear. Chloride: Dissolve 0.33 g in water with the addition of 1 ml of nitric acid and dilute to 30 ml with water. The resulting solution complies with the limit test for chlorides, Appendix 3.10 (750 ppm). Sulphate: Dissolve 0 :1 g in water with the addition of 3 ml of 2M hydrochloric acid, filter and dilute to 60 ml with water The resulting solution complies with the limit test for sulphates, Appendix 3 15 (0 6%) Loss on ignition