ANALAO 104 (1 241 ) 705-800 (1 979)ISSN 0003-2654August 1979THE ANALYSTTHE ANALYTICAL JOURNAL OF THE CHEMICAL SOCIETYCONTENTS705 Electrochemical Studies of Strongly Chelating Anthraquinone Derivatives-G. Ali Qureshi, G. Svehla and M. A. Leonard723 Direct Differential-pulse Polarographic Determination o f Mixtures o f theFood Colouring Matters Tartrazine - Sunset Yellow FCF, Tartrazine - GreenS and Amaranth - Green S in Soft Drinks-A. G. Fogg and K. S. Yo0730 Ion-selective Polymeric-membrane Electrodes with lmmobilised lon-exchangeDevelopment of a Calcium Electrode-L. Ebdon, A. T. Ellis Sites.and G. C. CorfieldPart I.739 High-frequency Microtitrimetric Determination o f Acidic and Basic Constituentsin Lubricating Oils. Part II. Determination o f Total Base Number-T.FernBndez, J.M. Rocha, N. Rufino, A. Garcia Luis and F. Garcia Montelongo750 Continuous Solvent-extraction Method f o r the Spectrophotometric Deter-mination o f Cationic Surfactants-J iro Kawase and Makoto Yamanaka756 Automatic Emission Spectrometer f o r the Determination of Nitrogen-I 5-J. D. S. Goulden and D. N. Salter766 Studies in Gas Chromatography - Chemical Ionisation Mass Spectrometry o fSome Silicate Anions-J. B. Addison771 Internal Standardisation and i t s Value in the Assessment o f the Suitability o fthe Co I u m n f o r Qua n t i t a t i ve H i g h - perform an ce L i q u i d C h r o ma t o g ra p hy-R. A. MooreREPORT BY THE ANALYTICAL METHODS COMMITTEEDetermination of Small Amounts o f Selenium in Organic Matter 778SHORT PAPERS788 Hydrocarbon Analysis of Naphtha Using Capillary-column Gas Chromato-graphy Under Isothermal Conditions-Pradeep Kumar, S. L. S. Sarowha andP. L. Gupta792 The Impact Cup: A Simple Aid in Flame Spectrometric Analysis a t High AnalyteConcentrations-Malcolm S. Cresser797 Book ReviewsSummaries o f Papers in this Issue-Pages iv, vi, vii, x, x i iPrinted by Heffers Printers Ltd Cambridge EnglandEntered as Second Class a t New York, USA, Post Offic