a platinum or mercury indicator electrode and a mercury - mercurous sulphate reference electrode. Ignore any preliminary inflection

Weigh accurately about 250 mg, dissolve in a mixture of 25 ml of alkaline borate buffer pH 9.0 and 0.5 ml of acetic anhydride by stirring for 3 minutes, add 10 ml of acetate buffer pH 4.6 and titrate immediately with 0.02M mercuric nitrate, determining the end-point potentiometrically with a platinum or mercury indicator electrode and a mercury - mercurous sulphate reference electrode. Ignore any preliminary inflection in the titration curve. Each ml of 0.02M mercuric nitrate is equivalent to 0.007748 g of degradation products calculated as C C16H18NaO5S. 2-Ethylhexanoic acid. Not more than 2.0%, determined by the following method. Carry out the method for gas chromatography, Appendix 4.2, injecting 1 ul of each of the following solutions. Prepare a 1.0% w/v solution of valeric acid (internal standard) in hexane (solution A). For solution (1) dissolve 1.0 g of the substance being examined in 5 ml of water in a glass-stoppered flask, add 3 ml of 2M hydrochloric acid, 1 ml of solution A and 5 ml of hexane, shake vigorously for 1 minute, centrifuge if necessary and use the clear supernatant layer. Solutions (2) and (3) are prepared in thesame manner but using an extra 1 ml of hexane in place of solution A for solution (2) and 20 mg of 2 ethylhexanoic acid suspended in 5 ml of water in place of the substance being examined for solution (3). The chromatographic procedure may be carried out using (a) a column (1.8 m x 4 mm) packed with a support impregnated with a stationary phase suitable for the separation of free fatty acaidsa (a column containing 10% of SP 1200 and 1% of phosphoric acid on Chromosorb W AW, 80-100 mesh, is suitable) and maintained at 145° with detector temperature of 150°, (b) a flame lonisation detector maintained at 150° and (c) a flow rate of 45 ml per minute of the carrier gas. Water: Not more than 4.0% w/w, determined on 0.4 g, Appendix 3.24 Assay. Weigh accurately about 50 mg, dissolve in 1.0 ml of alkaline