λ MAJOR ADVANCE in the

measurement 01 PARTICLE SIZE DISTRIBUTION

from CAHN

• FAST • AUTOMATIC unattended • HIGH ACCURACY

& PRECISION • SAMPLES FROM 10mg-2g • 1-100 μ

• EASY CALCULATIONS

The new Cahn Particle Sedimentation System is a major advance in par­ticle size instrumentation. It is an automatic recording sedimentation balance incorporating the latest theoretical and experimental ad­vances in this rigorously correct and highly regarded technique. It yields weight percent as a function of equivalent Stokes d iameter . . . and agrees closely with other sedimenta­tion methods, permitting easy tran­sition from them and immediate use of its data.

Phone or Write for details

7500 Jefferson St., Paramount, Calif. 90723 (213) 634-1935

27 Essex Rd., Dartford, Kent, U.K., Ph. 21540

MEETINGS

first in which ion-selective electrodes have been used with radioactive solu­tions. It is encouraging that no de­leterious 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 par­ticularly stressing the high sensitivity and great promise of these new meth­ods, he nevertheless noted some inher­ent 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 com­fortably 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 reac­tions, E. Ricci reviewed the 3He-activa-tion program of Oak Ridge National Laboratory, and C. Engelmann de­scribed his facilities at the CEN, Saclay, France. Then followed four presenta­tions related to photon-activation anal­ysis. 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 experi­ments, and E. Schweikert discussed photon activation of heavy elements. Finally, J. E. Strain (ORNL) com­mented on high-yield tritium targets for 14-MeV neutron generators. A number of important details of non-reactor methods of analysis were devel­oped through discussion by both panel members and audience—e.g., the neu­tron spectrum produced by brems-strahlung targets in electron acceler­ators, the channeling effects in cbarged-particle activation analysis, and, for this method, the comparative merits of the mathematical treatments of Engle-mann and of Ricci-Hahn. The inter­est 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 Apa­thy in Isotope Applications: What Can Be Done?" was moderated by P. S. Baker, Editor of Isotopes and Radia­tion 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 pro­vocative that a separate summary of the session is being prepared for pub­lication.

If apathy in isotope applications is indeed a general trend, there was cer­tainly no evidence for it in the nuclear and radiochemical sessions of the con­ference. Low level determinations, both with liquid and plastic scintillators, were discussed by Landgrebe and Rod-riguez-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 <0.00f ppm. Electrolytic calibration is used.

J. L. Botts (ORNL) also described an application of GLC that created considerable interest. He has inter­faced a vacuum fusion apparatus with a gas chromatograph and used the com­bined units to determine interstitial gases in numerous refractory alloys. Transfer of the gases evolved within the

7 2 A · ANALYTICAL CHEMISTRY

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CAHN INSTRUMENT C O M P A N Y

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