xiv SUMMARIES OF PAPERS IN THIS ISSUE [November, 1971Determination of Orthophosphate in the Presence of Nitrate IonsA method is described for the spectrophotometric determination oforthophosphate in the presence of nitrate. Reduction of nitrate ions toammonia is effected by aluminium metal and sodium hydroxide solution,and after the removal of all the ammonia produced (by heating) the phos-phate is determined by the formation of the phosphomolybdate complexand reduction to molybdenum blue. The method is suitable for the deter-mination of orthophosphate a t a concentration of M in the presence ofmore than 10-1 M of nitrate. I t also overcomes interference by fluoride andother halide ions in the molybdenum-blue method.E. J. DUFF and J. L. STUARTDepartment of Preventive Dentistry, Turner Dental School, The University,Manchester, M15 6FH.Analyst, 1971, 96, 802-806.The Determination of Epichlorohydrin in Aqueous Solutions in thePresence of Glycerin, Monochlorohydrin and GlycidolEpichlorohydrin can be extracted from aqueous solutions containingglycerin, monochlorohydrin and glycidol into carbon tetrachloride and deter-mined by infrared spectrophotometry.The high-frequency component ofthe complex band a t a wavenumber 1274 cm-l is used as the analytical band.A three-fold excess of carbon tetrachloride over the aqueous phase is necessaryfor the quantitative extraction. A cell thickness of up to 1 mm can be used; theconcentration limit of the solute in the aqueous phase is then 0.3 per cent.v/v.PETR ADAMEKInstitute of Chemical Technology, Prague 6, Czechoslovakia.and VLASTIMIL PETERKAResearch Institute of the Fat Industry, Rakovnik, Czechoslovakia.Analyst, 1971, 96, 807-809.The Use of Back- flushing with Electron-capture GasChromatographyAn apparatus is described that enables materials with a longer retentiontime than those of interest to be back-flushed out of electron-capture gaschromatographs. Shorter analysis times, a longer column life and lessfrequent cleaning of the detectors have been achieved with this device.B. T. CROLLThe Water Research Association, Medmenham, Marlow, Buckinghamshire.Analyst, 1971, 96, 810-813.An Enzymic Method for the Determination of Dried SkimmedMilk in Mashed Potato PowdersAn enzymic method is described for the determination of dried skimmedmilk in mashed potato powders. The method is based on the determinationof free lactose by its hydrolysis with /iI-galactosidase, the glucose formedbeing determined by the hexokinase method. The determination is freeof interference from varying concentrations of reducing sugars found indried potatoes. Accuracy and reliability are greater with this method thanwith other methods currently in use.R. K. BAHLJ. Sainsbury Ltd., Stamford House, Stamford Street, London, S.E.1.Analyst, 1971, 96, 814-816.The Determination of Carbarsone in Animal FeedsReport prepared by the Prophylactics in Animal Feeds Sub-committee.ANALYTICAL METHODS COMMITTEE9/10 Savile Row, London, W1X 1AF.Analyst, 1971, 96, 817-823