QUARTERLY REVIEWS VOL. IV 1950 Committee of Publication Chairman .- SIR CYRIL HINSRELWOOD M.A. Sc.D. D.Sc. F.R.S. SIR WALLACE Aroe~s C.B.E. B.A. R. P. BELL M.A. B.Sc. F.R.S. G. M. BENNETT C.B. M.A. Sc.D. F. BERGEL D.Phil.Nat. D.Sc. E. J. BOWEN M.A. D.Sc. F.R.S. H. BURTON Ph.D. D.Sc. F.R.I.C. A. H. COOK Ph.D. D.Sc. F.R.I.C. F. S. DAINTON M.A. Ph.D. C. W. DAVIES D.Sc. F.R.I.C. M. G. EVANS D.Sc. F.R.S. D LL. HAMMICIC M.A. D.Sc. R. D. HAWORTH D.Sc. Ph.D. F.R.S. D. H. HEY Ph.D. D.Sc. F.R.I.C. E. D. HUGHES D.Sc. F.R.S. R. P. L~STEAD C.B.E. M.A. D.Sc. H. W. MELVILLE Ph.D. D.Sc. F.R.S. L. N. OWEN Ph.D. D.Sc. F.R.I.C. D.Sc. F.R.I.C. F.R.S. F.R.I.C. F.R.S. S. PEAT Ph.D. D.Sc. F.R.S. S. G. P. PLANT D.Phil. M.A. B.Sc. E. HI. RIDE& F.R.S. M.B.E. M.A. D.Sc. J. M. ROBERTSON M.A. D.Sc. F. L. ROSE O.B.E.Ph.D. D.Sc. H.N. RYDON,D.SC. D.Phil.,F.R.I.C. C. W. SHOPPEE D.Sc. D.Phil. R. SPENPE Ph.D. D.Sc. F.R.I.C. D. W. G. STYLE Ph.D. A. R. TODD M.A. D.Sc. F.R.S. J. WALKER Ph.D. D.Phil. D.Sc. W. WARDLAW C.B.E. D.Sc. T. S. WHEELER Ph.D. D.Sc. F. G. YOUNG M.A. D.Sc. F.R.S. F.R.S. F.R.I.C. F.R.I.C. F.R.I.C. F.R.I.C. F.R.I.C. Editor R. S. CAHN M.A. D.Phil.Nat. F.R.I.C. Assistant Editors A. D. MITCHELL D.Sc. F.R.I.C. L. C. CROSS Ph.D. A.R.C.S. F.R.I.C. Indexer MARGARET LE PLA B.Sc. L O N D O N T H E C H E M I C A L S O C I E T Y CONTENTS PAUE THE EMISSION SPECTRA OF FLAMES. By A. G. GAYDON . 1 CHEMISTRY OF THE TRANSURANIC ELEMENTS. By M. W. LISTER . . 20 BIOGENETIC ORIGIIN OF THE PSRROLE PIGI~NTS. By P. MAITLAND . . 46 THE REDUCTION OF ORGANIC COMPOUNDS BY METAL-AMMONIA SOLUTIONS.By ARTHUR J. BIRCH. . 69 RELATION BETWEEN THE OXIDATION-REDUCTION POTENTIALS OF QUINONES AND THEIR CHEMICAL STRUCTURE. By M. G. EVANS and J. DE HEER . . 94 INTERHALOUEN C O M P O ~ S AND POLYHALIDES. By A. G. SHARPE . . 115 ROTATION SPECTRA. By D. H. WHIFFEN . 131 LIMIT~G DENSITIES. By R. WEYTLAW-GRAY . . 153 ISOTOPIC TRACER TECH*~IQUE. By H. R. V. ARNSTEIN and R. BENTLEY . . 172 So= ASPECTS OF FURAN PYRAN CHEMISTRY. By D. G. JONES and A. W. C. TAYLOR 195 ORGANOMETALLIC COMPOUNDS OF THE FIRST THREE PERIODIC LIGHT ABSORPTION AND PHOTOCHEMISTRY (including photo- polperisation and the effects of light on dyes). By E. 5. BOWEN . 236 SOME ORGANIC PEROXIDES AND THEIR REACTIONS. By E. G. E. HAWEINS . . 251 STRUCTURE AND ACTIVITY IN SYNTHETIC INSECTICIDES. By W. A. SEXTON . . 272 By G.M. BURNETT . . 292 THE CYANINE DYES. By F. M. HAMER . . 327 MELTING AND CRYSTAL STRUCTURE. By A. R. UBBELOHDE . 356 THE NITRATION OF HETEROCYCLIC NITROGEN COMPOUNDS. By K. SCHOFIELD . . 382 ANIONOTROPY. By E. A. BRATJDE . . 404 GROUPS. By G. E. COATES . . 217 RATE CONSTANTS IN RADICAL POLYMERISATION REACTIONS. QUARTERLY REVIEWS THE CHEMICAL SOCIETY PATRON HIS MAJESTY THE KING President E. K. RIDEAL M.B.E. M.A. D.Sc. F.R.S. Vice-Presidents who have filled the office of President F. G. DONNAN C.B.E. D.Sc. LL.D. SIR IAN HEILBRON D.S.O. D.Sc. SIR CYRIL HINSHELWOOD M.A. F.R.S. LL.D. F.R.S. Sc.D. F.R.S. W. H. MILLS M.A. Sc.D. F.R.S. SIR ROBERT ROBINSON O.M. D.Sc. N. V. SIDGWICK C.B.E. D.Sc. LL.D. F.R.S. LL.D. F.R.S. Vice-Presidents R. P. BELL M.A. B.Sc. F.R.S. G. M.BENNETT C.B. M.A. Sc.D. J. W. COOK D.Sc. F.R.I.C. F.R.S. F.R.S. R. P. LINSTEAD C.B.E. M.A. D.Sc. A. R. TODD M.A. D.Sc. F.R.S. W. WARDLAW C.B.E. D.Sc. F.R.S. F.R.I.C. Treasurer SIR WALLACE AKERS C.B.E. B.A. D.Sc. F.R.I.C. Secretaries D. H HEY Ph.D. D.Sc. F.R.I.C. I H. BURTON Ph.D. D.Sc. F.R.I.C. E. D. HUGHES D.Sc. F.R.S. Ordinary Members of Council J. S. ANDERSON M.Sc. Ph.D. G. BADDELEY M.Sc. Ph.D. C. E. H. BAWN B.Sc. Ph.D. L. L. BIRCUMSHAW M.A. D.Sc. G. R. CLEMO D.Phil. D.Sc. A. H. COOK Ph.D. D.Sc. F.R.I.C. L. HUNTER Ph.D. D.Sc. F.R.I.C. F. E. KING M.A. D.Phil. D.Sc. T. MALEIN Ph.D. D.Sc. F.R.I.C. L. N. OWEN Ph.D. D.Se. F.R.I.C. A.R.C.S. F.R.S. E. G. V. PERCIVAL Ph.D. D.Sc. J. D. ROSE M.A. B.Sc. R. SPENCE Ph.D. D.Sc. F.R.I.C. F. S. SPRING Ph.D. D.Sc. F.R.I.C. M. STACEY Ph.D. D.Sc. F.R.S. L. E. SUTTON M.A. D.Phil. F.R.S. A. I. VOGEL D.Sc. D.I.C. F.R.I.C. J. WALKER Ph.D. D.Phil. D.Sc. W. A. WATERS M.A. Sc.D. F.R.I.C. T. S. WHEELER Ph.V. D.Sc. F.R.I.C. GWYN WILLIAMS D.Sc. Ph.D. F.R.I.C. Ex-Officio Members of Council H. E. Cox D.Sc. Ph.D. F.R.I.C. (Chairman of the Joint Libra3 Committee). A. FINDLAY C.B.E. D.Sc. LL.D. F.R.I.C. (Chairman of the Chemical Council). L. H. LAPMPITT D.Sc. F.R.I.C. (Chairman of the Bureau of Abstracts). General Secretary J. R. RUCK KEENE M.B.E. B.A. Telephone Numbers Regent 1676/6 Librarian A. E. CUMMINS. Printed in Great Britain by Butler & Tanner Ltd. Frome and London