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10 on Readers' Service Card. NEW BOOKS to 4 X 1010 ergs ... R. M. Lange, Wright Air Develop- ment Division, U. S. Air Force. PB. 171 401. September 19...
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NEW BOOKS to 4 χ 1010 ergs per gram carbon. Further investigation is recommended to develop the systems. Calibration, reproducibility, sensitivity to impuri­ ties, dose rate dependence, and irradi­ ation to higher dose levels are facts which should be considered. Molecular Weight Determination in the Characterization of Polymers.

R. M. Lange, Wright Air Develop­ ment Division, U. S. Air Force. PB 171401. September I960. 28 pages. 75 cents.

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ANALYTICAL CHEMISTRY

Preliminary results and recommenda­ tions for future study are given on the determination of the molecular weight of poly-(dimethyl-2 ; 2-dimethylene pimelate) prepared by solution polymeri­ zation to 40% conversion. Techniques used in the study included osmometry, light-scattering, viscometry and frac­ tional precipitation. Osmotic pressure measurements on a sample of the whole polymer in toluene solution gave a number-average molecular weight of 3.36 X 10s grams/mole. Some light-scattering measurements showed a weight-average molecular weight of 2.80 X 106 grams/mole. The heterogeneity index (M w /M n ) indi­ cated a broad distribution of molecu­ lar weights. It was recommended that in future light-scattering studies cy­ lindrical cells rather than semi-octag­ onal cells be used and that equipment be developed for determining the weight-average molecular weight of very small quantities of material in the range of 0.010-0.500 gram. Theoretical and Experimental In­ vestigation of Radioactive Ion­ ization Gauges. M. A. El-Moslimany, University 0} Michigan, for Air Research and Development Com­ mand. PB 171 105. May I960. 183 pages. $3.00. As part of a systematic study of radioactive ionization gages, the chief ionic and electronic processes encoun­ tered are briefly reviewed. A relation­ ship between the collected ion current and the gas pressure is analytically de­ veloped for a planar configuration, considering the probability of electron attachment as a function of the elec­ tric field intensity and the gas pres­ sure. In calculating the theoretical current-pressure curves, the numerical values used for ionic mobilities and the recombination coefficient are those used for different mixtures of nitrogen and oxygen. Experimental current-pres­ sure curves are found to be in fair agreement with the theoretical results. Two radioactive ionization gauges were