:ι·\\Ί λ MAJOR ADVANCE in the
measurement 01
PARTICLE SIZE DISTRIBUTION from CAHN
• FAST • AUTOMATIC unattended • HIGH ACCURACY & PRECISION • SAMPLES FROM 1 0 m g - 2 g • 1-100 μ • EASY CALCULATIONS The new Cahn Particle Sedimentation System is a major advance in par ticle size instrumentation. It is an automatic recording sedimentation balance incorporating the latest theoretical and experimental ad vances in this rigorously correct and highly regarded technique. It yields weight percent as a function of equivalent Stokes d i a m e t e r . . . and agrees closely with other sedimenta tion methods, permitting easy tran sition from them and immediate use of its data.
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CAHN INSTRUMENT
COMPANY
7500 Jefferson St., Paramount, Calif. 90723 (213) 634-1935 27 Essex Rd., Dartford, Kent, U.K., Ph. 21540 Circle No. 23 on Readers' Service Card
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ANALYTICAL CHEMISTRY
MEETINGS
first in which ion-selective electrodes have been used with radioactive solu tions. It is encouraging that no de leterious effects were noted. A period for open discussion followed these three papers, with the three authors seated before the audience. This question, answer, comment period was lively and spontaneous. The session had to be terminated at the lunch-hour, but the discussion continued in small groups throughout the conference. Another portion of the program that created a great deal of interest was a panel discussion on nonreactor methods of activation analysis. This session ojiened with an invited lecture by Ph. Albert (CNRS, France) during which he examined the present status and future outlook of chargcd-particle and photon activation analysis. While par ticularly stressing the high sensitivity and great promise of these new meth ods, he nevertheless noted some inher ent pitfalls which he urged analysts to avoid through study and experience. This lecture was followed by a very lively panel discussion, moderated by W. S. Lyon (ORNL). Each of the panel members gave a short talk about a problem of his specialty, and a com fortably long question and answer period followed each presentation. The first three speakers discussed different aspects of the use of charged particles in analysis. O. TJ. Anders (Dow) talked about results of measurements of prompt particles from nuclear reac tions, E. Ricci reviewed the 3 He-activation program of Oak Ridge National Laboratory, and C. Engelmann de scribed his facilities at the CEN, Saclay, France. Then followed four presenta tions related to photon-activation anal ysis. G. J. Lutz and F. A. Lundgren discussed the tungsten converter used at the National Bureau of Standards and results obtained with it. H. R. Lukens (General Atomic) presented data from photo-excitation experi ments, and E. Schweikert discussed photon activation of heavy elements. Finally, J. E. Strain (ORNL) com mented on high-yield tritium targets for 14-MeV neutron generators. A number of important details of nonreactor methods of analysis were devel oped through discussion by both panel members and audience—e.g., the neu tron spectrum produced by bremsstrahlung targets in electron acceler ators, the channeling effects in cbargedparticle activation analysis, and, for this method, the comparative merits of the mathematical treatments of Englemann and of Ricci-Hahn. The inter est created by the panel program, which began at 2 pm, was such that, despite its length, there were thirty persons
present at the time the session was adjourned, after 6 pm. A second panel discussion, "The Apa thy in Isotope Applications: What Can Be Done?" was moderated by P. S. Baker, Editor of Isotopes and Radia tion Technology. Although opinions and suggestions were clearly divergent, the "apathy" was recognized as a very real problem. Many elements of the discussion were so stimulating and pro vocative that a separate summary of the session is being prepared for pub lication. If apathy in isotope applications is indeed a general trend, there was cer tainly no evidence for it in the nuclear and radiochemical sessions of the con ference. Low level determinations, both with liquid and plastic scintillators, were discussed by Landgrebe and Rodriguez-Pasqués (NBS) and Oestmann (Argonne). Currie (NBS) presented an interesting statistical approach for reporting trace amounts of radioactivity. Chemical and fission product measurements at the Dragon HTR were discussed in two papers by Gray and Reed (Dragon Project Office, Dorset). A variety of chemical and radiochemical species were investigated. A number of novel isotope applications to water conservation were presented by Smith (USDA). He showed how nuclear equipment and methods can be applied to snow-pack analysis and, as a result of his investigations, many previous "laws" of snow-water systems appear to have questionable validity. Two applications of gas-liquid chromatography deserve special mention. R. E. Johnson (AEC Ltd, Chalk River) described instrumentation for the in-line determination of dissolved gases in aqueous samples. The application of OLC to aqueous systems is a difficult, but extremely promising, field of study at the present time. The approach reported here involved partitioning of the dissolved gases in the sample between water and ultrapure ethane, then routing the stripping gas into a gas chromatograph for separation and estimation. This technique has been under test for several years and has proved to be quite satisfactory provided the equipment is carefully designed and fabricated. Detection limits for hydrogen, oxygen, and nitrogen are
