ANALYTICAL CHEMISTRY
EDITORIAL
August 1961, Vol. 33, N o . 9 A P P L I E D JOURNALS, ACS Director of Publications, C. B. Larrabee Editorial Director, Richard L. Kenyon Assistant to the Director of Publications, Joseph H. Kuney Assistant to the Editorial Director, Rodney N . Hader Director of Editorial Research, Robert F. Gould
ANALYTICAL
CHEMISTRY
Editor, LAWRENCE T . HALLETT
Managing Editor, ROBERT G. GIBBS
EDITORIAL
Cross-Checking Essential in Analysis
HEADQUARTERS
WASHINGTON 6, D . C. 1155 Sixteenth St., N.W. Phone REpublic 7-3337 Teletype WA 23 Associate Editors: G. Gladys Gordon, Stella Anderson, Katherine I. Biggs, Sue M. Solliday, Ruth Reynard Assistant Editors: Robert J. Kelley, Malvina B. Lester Editorial Assistants: Katherine H. Ginnane, Virginia E. Stewart, Lorraine M. Bertuzzi Layout and Production: Joseph Jacobs (Art Director), Melvin D . Buckner, Betty V. Kieffer, John V. Sinnett Editorial Reference; Barbara A. Gallagher
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APPLICATION
OF PHYSICAL METHODS t o t h e m e a s u r e m e n t of atomic
masses h a s shown t h a t m a n y of t h e generally accepted values for atomic weights are n o t so accurate as formerly believed. A substantial percentage of atomic weight determinations was made b y classical chemical methods. Between 1905 and 1946, for ex ample, the preparation and analysis of a series of chlorides and bromides led to t h e determination of atomic weights of 64 elements. M u c h of the painstaking research on these determinations w a s carried out in t h e laboratories of T . W . Richards, G. P . Baxter, a n d 0 . Hônigschmid. Because so much of t h e work w a s done a t H a r v a r d University, t h e method used was called t h e H a r v a r d method. Development of accurate physical methods for measuring atomic masses provided an independent check of t h e results of t h e chemical analytical methods used earlier for atomic weight determinations. I n struments such as t h e mass spectrometer were n o t available a t t h e time the original work was done. N e w values showed t h a t t h e chemical methods were not so accurate as previously believed. T h i s is not to say t h a t instrumental methods alone are t h e answer, as these methods m a y have their own systematic errors. T h e combination, however, of chemical and physical approaches gives more reliable results. Based on the newer results, a recheck of t h e H a r v a r d method established t h e existence of systematic errors. Once t h e existence of these errors was proved, it was possible t o recheck t h e chemical method and pinpoint t h e sources of systematic errors. Details appear in t h e " R e port for Analytical Chemists," page 23 A. These refinements a r e of value as there are still m a n y atomic weights whose values have not y e t been definitely determined. T h a t these errors occurred in spite of t h e most careful a n d painstaking attention to details by giants in t h e field, reaffirms t h e need for independent verification of results b y alternative methods. T o d a y , with the host of chemical and physical methods and instruments available, most work can be checked.
Contributing Editor: R. H. Müller Advisory Board: F . E. Beamish, C. E. Bricker, D . D. DeFord, E. C. Dunlop, C. L. Luke, W. J. Mader, H. V. Malmstadt, W. B. Mason, F. W. Mitchell, Jr., M. L. Moss, Ν . Η. Nachtrieb, L. B. Rogers, B. F. Scribner, Sidney Siggia, F. H. Stross Advertising Management R E I N H O L D PUBLISHING CORP. (For Branch Offices see page 131 A) VOL. 33, NO. 9, AUGUST 1961 · 1 1 3 7
