xii SUMMARIES OF PAPERS I N THIS ISSUEModified Methylene Blue Method for the Micro - determinationof Hydrogen Sulphide[September, 1974A method is described whereby hydrogen sulphide can be determinedsimply and rapidly in the 0.04 to 0.4 pmol range.N. A. MATHESONRowett Research Institute, Bucksburn, Aberdeen, AB2 9SB.Analyst, 1974, 99, 577-579.The Determination of Nitrogen- 15 in Plant Material With anEmission SpectrometerInstrumental and procedural modifications for the use of the Statron,Model NOI-5, emission spectrometer in the determination of nitrogen- 15 arereported. An interpolative method is recommended for estimating thebackground of the nitrogen-14 - nitrogen-15 peak. This method gives alinear relationship between apparent percentage of nitrogen- 15 and the actualpercentage of nitrogen-15 over the lower, most commonly used range.Assaysrepeated at intervals over 2 months had standard errors of 0-75 per cent.The preparation of nitrogen gas samples for the emission spectrometerhas been treated as a separate operation from the determination of total plantnitrogen. After a standard Kjeldahl digestion of the plant material, theammonium ion is precipitated with a Nessler reagent. The supernatant isrejected and the precipitate treated with dilute hydrochloric acid to give anammonium chloride solution, from which an aliquot is taken for a Dumascombustion in a discharge tube. Two operators can prepare and measure upto fifty samples per day. The method has been used to analyse a range of planttissues from an apple nutrition experiment, during which replicate digestionsand analyses gave values for nitrogen- 15 enrichment that differed by anaverage of only 2.5 per cent.C.P. LLOYD-JONES, G. A. HUDD and D. G. HILL-COTTINGHAMUniversity of Bristol, Department of Agriculture and Horticulture, Research Station,Long Ashton, Bristol, BS18 9AF.Analyst, 1974, 99, 580-587.Atomic-absorption Determination of Some Common Trace Elementsin Aluminium Oxide and Other Aluminium Compounds Using aCo-precipitation Separation TechniqueAtomic-absorption spectroscopy has been used to determine micro-gram amounts of calcium, iron, manganese, silicon, titanium, vanadiumand zinc in aluminium oxide and other aluminium-rich materials after co-precipitation of these elements on zirconium hydroxide from an alkaline solu-tion of the sample.The proposed method serves both to separate the trace elements fromaluminium and also to concentrate the elements, thus improving bothaccuracy and sensitivity.The method is shown to be as accurate andprecise as colorimetric procedures, very much quicker and less tedious.The trace constituents are determined in the range 5 to 400 pg in thefinal 25 ml of sample solution on a 2-g sample of aluminium oxide, and in therange 10 to 2000 pg on a 0.5-g sample of other materials (25-ml final volume).Interference effects are reduced to a minimum by separation of theelements from aluminium and the provision of closely matched standardsolutions.P. N.W. YOUNGNew Zealand Aluminium Smelters Limited, Invercargill, New Zealand.Analyst, 1974, 99, 588-594September, 19741 SUMMARIES OF PAPERS I N THIS ISSUEAtomic-absorption Studies on the Determination of Antimony,Arsenic, Bismuth, Germanium, Lead, Selenium, Tellurium and Tinby Utilising the Generation of Covalent HydridesA method for the determination of arsenic, bismuth, germanium, lead,antimony, selenium, tin and tellurium by means of hydride generation isdescribed. The hydrides are generated by adding the acidified sample todilute (1 percent. m/V) sodium borohydride solution. The liberated hydridesare passed directly into a 17 cm long silica tube mounted in an air - acetyleneflame. The advantages of the proposed system are its simplicity, highsensitivity, high speed of analysis and the fact that background correctionfacilities are not required.The generation of plumbane for analytical purposes does not appearto have been reported previously.K.C. THOMPSON and D. R. THOMERSONShandon Southern Instruments Ltd., Frimley Road, Camberley, Surrey, GU16 5ET.Analyst, 1974, 99, 595-601.Electrolytic Extraction Combined With Flame Atomic Absorptionfor the Determination of Metal Ions in Aqueous SolutionMetals were deposited from aqueous solutions onto an iridium wire eitherby electrolysis at pH 2 or by auto-deposition at pH 9. The amount depositedwas determined by atomisation with an air - hydrogen flame into a long-tube(10 cm) atomic-absorption spectrophotometer. The sensitivities obtained byelectrolysis were comparable with those obtained by conventional sampleaspiration for magnesium, lead and zinc and an order of magnitude greater forcadmium, copper and mercury. The presence of other ions in the samplesolution generally reduced the sensitivity of the method.J.B. DAWSON, D. J. ELLIS and T. F. HARTLEYDepartment of Medical Physics, General Infirmary, Leeds, LS 1 3EX.Mrs. M. E. A. EVANS and K. W. METCALFJohnson Matthey & Co. Ltd., Group Research Laboratory, Wembley, Middlesex.Analyst, 1974, 99, 602-607.A Potentiometric Titration Method for the Rapid Determinationof Salt in Meat ProductsA method is described for the rapid determination of salt in meat pro-ducts by titration of the macerated sample with silver nitrate. The acidicand oxidising conditions specified permit the use of an ion-selectiveelectrode with a silver sulphide membrane in the potentiometric detectionof the end-point. The method is slightly more precise and very much morerapid than existing routine and reference methods.M. KAPEL and J., C. FRYProcter Department of Food and Leather Science, Leeds University, Leeds, LS2 9 JT.An~lyst, 1974, 99, 608-611.The Use of Filter-papers in the Determination of Nitrogen in FoodsD. PEARSONNational College of Food Technology, University of Reading, St. George’s Avenue,Weybridge, Surrey.Analyst, 1974, 99, 612.xii