A The infra-red absorption spectrum, Appendix 5.4, is concordani wilh the reference spectrum of carbimazole or with the spectrum obtained from carbima

odour, characteristic Solubility Freely soluble in chloroform; soluble in acelone; sparingly soluble in ethanol (95%), slightly soluble in water and in ether Storage Store in well-closed containerst. STANDARDSCarbimazole contams not less than 98.5 per cent and not more than 100.5 per cent of C7H10N202S, calculated with reference to tne dried substance Idenlification A The infra-red absorption spectrum, Appendix 5.4, is concordani wilh the reference spectrum of carbimazole or with the spectrum obtained from carbimazole RS. B: Heat 0.2 g with 5 ml of dilule hydrochloric acid on a water-bath for 1 hour. Cool, extract with three quantities, each of 5 ml, of chloroform, wash he combined chloroform extracts with 0.5 ml of water, filter through a dry filter paper and remove the chloroform The residue, after crystallisation from ethanol (95%), melts at about 140°, Appendix 8.8. C: To a small quantity add 1 drop of dilute potassium iodobismuthate solution, a scarlet colour is produced. Methimazole: Carry out the method for thin-layer chromatography, Appendix 4.6, using silica gel G as the coating substance and a mixture of 80 volumes of chloroform and 20 volumes of acetone as the mobile phase. Apply separately to the plate 10 ul of eachof two solutions in chloroform containing (1) 1 0% w/v of the substance being examined and (2) 0005% w/v of methimazole RS and develop immediately. After removal of the plate, allow it to dry in air and spray with dilute potassium mdobismuthate solution Any spot corresponding to methimazole in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram oblamed with solution (2) Sulphated ash: Nol more than 0 1 %, Appendix 3 22 Loss on drying Nol more than 0 5%, determined on 1 g by drying over phosphorus pentoxide at a pressure not exceeding 0.7 kPa for 24 hours, Appendix 8.6. Assay: Weigh accurately about 50 mg and dissolve in sufficient water to produce 500 0 ml To 10 0 ml of the solulion add 10 ml of IM hydrochloric acid and sufficient water to produce 100 0 ml and measure the absorbance of the resulting solution at the maximum at about 291 nm, Appendix 5.5 Calculate the content of C7H10N202S taking 557 as the value of A(1%, 1 cm) at the maximum at about 291 nm CARBIMAZOLE TABLETS Usual strengths: 5 mg, 20 mg. Storage: Slore in well-closed containers in a cool place STANDARDSCarbimazole Tablels contain not less than 90 0 per cent and not more than 110.0 per cent of the stated amount of carbimazole, C7H10N202S. The tablets may be coated. Identification: A: Shake a quantity of the powdered tablets equivalent of 50 mg of Carbimazole with two quantities, each of 5 ml of chloroform. Combine the chloroform extracts, filter and evaporate the filtrate to dryness. The infra-red absorption speclrum of the residue, Appendix 5.4, after drying al 60° at a pressure nol exceeding 0.7 kPa for 30 minutes, is concordani with the reference spectrum of carbimazole or with the spectrum obtained from carbimazole RS. B: To a small quantity of the powdered tablets add 1 drop of dilute polassium iodobismuthate solution; a scarlet colour is produced. Methimazole: Comply with the test described under Carbimazole, using as solution (1) a solution prepared by shaking a quantity of the powdered tablets equivalent to 10 mg of Carbimazole with 2 ml of chloroform for 5 minutes and filtering Uniformily of content (For tablets containing 10 mg or less): Comply with the requirements stated under Tablets using the following method of analysis Powder one tablet, add 300 ml of waler warmed to a lemperature nol exceeding 35°, shake for a few minutes and add sufficient water to produce 500 0 ml Mix well, filter, dilule further, if necessary wilh water and complele the Assay beginning al the words "Measure Ihe absorbance " Other requirements Comply with Ihe requirements of lests slated under Tablets. Assay: Weigh and powder 20 tablets. Weigh accurately a quantity of the powder equivalent to 40 mg of Carbimazole, add 300 ml of water warmed to a temperature not exceeding 35°, shake for a few mmutes and add sufficient water to produce 50.00 ml. Mix well and filler; dilute 50.0 ml of the filtrate to 500.0 ml with water and mix well. Measure]