ANALYTICAL CHEMISTRY
EDITORIAL
FEBRUARY 1958, Vol. 30, No. 2 APPLIED JOURNALS, ACS Director o f Publicafions, C. B. Lorrobee Editorial Director, Walter J. Murphy Execofive Edifor, Jomes M. Crowe Production Manager, Joseph H. Kuney ANALYTICAL CHEMISTRY Editor, Lawrence T. Hallett Managing Editor, Robert 0. Gibbs EDITORIAL HEADQUARTERS WASHINGTON 6, D. C. 1 1 55 Sixteenth St., N.W. Teletype WA 23 Phone Republic 7-5300 Associafe Edifors: 0. Gladys Gordon, Stello Anderson, Ruth Cornetfe, Kotherine 1. Biggs, George B. Krontz Assistant Editors: Betfy V. Kieffer, Arthur Poulos, Robert J. Riley, Robert J. Kelley, Hanns 1. Sperr, Ruth M. Howorth, Eugenia Keller, Sue M. Sollidoy Editorial Assisfanfs: Molvino B. Preiss, Morjorie H. Swenson, Ruth Reynard, Gloria H. Wills Staff Arfist: Melvin D. Buckner BRANCH EDITORIAL OFFICES CHICAGO 3, ILL. Room 926 36 South Wobosh Ave. Teletype CG 725 Phone State 2-5148 Associate Editors: Howord J. Sanders, Chester Plocek Asrisfanf Editor: Lourence J. White HOUSTON 2, TEX. 718 Melrose Bldg. Teletype HO 72 Phone Foirfox 3-7107 Associate Editor: Bruce F. Greek Arsistanf Editor: Earl V. Anderson NEW YORK 16, N. Y. 2 Park Ave. Phone Oregon 9-1646 Teletype NY 1-4726 Associate Editors: William 0. Hull, Horry Stenerson, David M. Kiefer, D. Groy Weaver, Walter S. Fedor, Morton Solkind Assirfant Editor: Louis A. Agnello SAN FRANCISCO 4, CALIF. 703 Mechonics’ Institute Bldg. 57 Post St. Teletype SF 549 Phone Exbrook 2-2895 Associate Editor: Richord G. Newhall Assisfanf Editor: David E. Gushee EASTON, PA. 20th ond Northompton Sts. Teletype ESTN Po 48 Phone Eoston 91 11 Associate Editor: Charlotte C. Soyre Ediforial Assisfants: Joyce A. Richards, Elizobeth R. Rufe, June A. Borron EUROPEAN OFFICE Bush House, Aldwych, London Cable JIECHEM Phone Temple Bar 3605 Associate Edifor: Albert S. Hester Contributing Edifor: R. H. Miiller Advisory Board: R. M. Archibold, W. H. Beomer, H. 0. Carsidy, W. D. Cooke, R. M. Fowler, l o u i s Gordon, J. 1. Hoffmon, M. T. Kelley, E. E. Leininger, W. M. MocNevin, V. W. Meloche, John Mitchell, Jr., E. J. Rosenboum, R. 0. Russell, A I Steyermork Advertising Managemenf: REINHOLD PUBLISHING CORP. 430 Pork Ave., N e w York 22, N. Y. (For Branch Offices see page 1 13 A]
New Analytical Methods Challenge -Old Ones
CLASSICAL
methods of determining elements or groups are based upon chemical reactions or decomposition under specified conditions. These methods, the result of years of research and testing by analytical chemists, are considered the standards by which all other methods are judged. Newer methods, based particularly on nondestructive physical approaches, are beginning to cast some doubt on the accuracy of some time-honored procedures. Thermal gravimetric studies by Duval, for example, have thrown much light on the composition of precipitates. His method has led to more reproducible and accurate results from ignition procedures. The older method of heating to constant weight without particular attention to heating conditions is giving way to heating to constant weight under carefully controlled conditions. By such methods we are learning more about the nature of water of crystallization and adsorption. As a result, heating can be better controlled to prevent decomposition of the sample. More recent is the utilization of nuclear magnetic resonance as a nondestructive method for determining adsorbed water and water in the molecules. Accuracy not heretofore attainable is possible. KMR avoids the errors which may result from decomposition during ignition. Infrared studies of functional groups are proving more accurate than some of the more conventional chemical methods. Viscosity measurements which differ depending on the method used, have long been a controversial subject. Kern data are becoming available in this area through use of ultrasonics. In conventional methods based on the falling ball, flow through tubes, and spinning cones, the molecules in the material being tested are subjected to various degrees of shearing stress. These stresses vary with different methods and therefore may give results which do not agree. Ultrasonic methods do not disrupt the system under study and so probably give a more accurate indication of true viscosity. The application of nondestructive physical methods to analysis will permit more accurate studies of molecules and their interactions. When the validity of results obtained using the newer physical methods is proved, the physical methods will probably become the standards by which chemical methods are judged. We are, of course, a long way from the analytical chemist’s goal of having a truly specific test for each determination. The newer methods being developed, however, hold much promise of attaining that goal.
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