NEWS
Preparative gas chromatography points to new standards of purity. And isolates workable quantities of fractions 99.99% pure. T h e Megachrom* is indeed a powerful new tool for research, handling large volume samples, and yielding ultra-pure fractions in significant quantities. M e g a c h r o m preparative gas chromatographs are offered by Beckman dealers everywhere... dealers qualified by factory training to provide complete assistance from the selection of equipment to meet the needs of your laboratory to service throughout the life of the instruments chosen. Write us for your dealer's n a m e and address and Data File ID-A-2.
Beckman®/ Beckman Instruments International, S.A. Rue des Pierres-du-Nitoii Genera. Switzerland
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State University, Detroit, October 16 to 18. A highlight of the Conference will be presentation of the Anachem Award for Outstanding Achievement in Analytical Chemistry to Dr. Izaak Maurits Kolthoff, University of Minnesota. Papers in the fields of instrumental, gravimetric, and volumetric analysis; fiuorometery; polarography ; emission, absorption, and x-ray spectroscopy; mass spectrometry, and chromatography, are sought. Special symposia are being planned on EDTA, clinical chemistry, and radiochemistry methods. All papers presented will remain the property of the authors and may be published by the authors in technical journals of their choice. Anyone desiring to present a paper should send to the Program Committee by April 3, 1961, title, author, estimate of presentation time (not to exceed 30 minutes), and an abstract (150 to 200 words). P. N. Burkard, Wyandotte Chemicals Corp., Wyandotte, Mich., is program chairman. Another important part of the conference will be more than 40 exhibits by major suppliers of laboratory equipment.
Carbon-14 Half Life Is 5760 Years A more accurate value for the half life of carbon-14—important in geological and archaeological dating—was obtained recently by the National Bureau of Standards. The new value is 5760 years, as compared with the previously accepted value of 5568 years. The redetermination involved quantitatively diluting high-specific-activity carbon dioxide for counting in lengthcompensated internal gas counters in the Geiger and proportional regions. Mass spectrometric analyses of parts of the undiluted gas sample were made to determine the isotopic abundance of carbon-14, which was found to be approximately 44 atom per cent. Experimental details of the redetermination will be published in the near future. Intercomparative measurements of the isotopic abundances were also carried out with the United Kingdom Atomic Energy Authority. The redetermined value is in fairly good agreement with the value of 5900 ±250 years obtained at NBS in 1953. The value of 5568 years that has been in use was somewhat arbitrarily chosen. Because of the wide range in measured values of the half life of carbon-14— from 4700 to 7200 years—a weighted average of three values determined by gas counting and by mass spectrometric
analysis was tentatively accepted for the purpose of radiocarbon dating of archaeological samples. Present measurements have led to the conclusion that the uncertainties in the values obtained experimentally may have arisen almost entirely from adsorption effects. The new value of 5760 years is of particular interest in assessing the age of, for example, the Dead Sea Scrolls. On the basis of the previously accepted half life, these scrolls were found to be 1917 ±200 years old, that is, dating to about 40 A.D. The new half life will place their age at 1983 years, dating them at about 20 B.C. The change, however, is less than the previously stated experimental error.
Analytical Methods Committee Report The Analytical Methods Committee of the Society for Analytical Chemistry has issued its report covering the year ending February 29, 1960. The committee, in existence since 1924, was established as a financially independent unit in 1954. Much of its financial support comes from industry. The committee now has 13 subcommittees. During 1959 the committee issued several reports which were published in The Analyst. These are: Radiochemical Investigations on the Recovery for Analysis of Trace Elements in Organic and Biological Materials; Determination of Lead; Notes on Perchloric Acid and Its Handling in Analytical Work; Determination of Tocopherols in Oils, Foods, and Feeding Stuffs, and Application of Gas-Liquid Chromatography to Essential Oil Analysis. Reports prepared by the Joint Committee of the Pharmaceutical Society and SAC were: Determination of the Capsaicin Content of Capsicum and Its Preparations; Determination of Rotenone in Rotenone-Bearing Plants with Special Reference to Lonchocarpus. A complete list of reports prepared and published in The Analyst since 1927 appears in the current annual report. "Recommended Methods for the Analysis of Trade Effluents" regularly published in The Analyst are now available in book form. These methods were prepared by a Joint Committee of the Association of British Chemical Manufacturers and the Society for Analytical Chemistry. The publisher is W. Heffer and Sons, Ltd., Cambridge, England. Further details of the work of the committee and investigations in prog-
Circle Mo. 17 on Readers' Service Card Circle No. 195 on Readers' Service Card 44 A
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