tained from experiments, some generalizations appeared. At higher temperatures, more cations in a fused mixture change to less active forms producing a less acidic effect, for example. In alkali fuses, high oxygen activity is characteristic. Prof. Erdey also covered work on pre-treatment of reagents and life of precipitates as these factors affect rate of precipitation and precipitate grain size. With precipitates such as barium sulfate, strontium sulfate, and calcium oxalate, aging increases grain size. This is due to a lower rate of nuclei formation and crystal growth. Adding nuclei-forming agents also will decrease grain size. Such results follow observations of the "nitration effect" experienced on fine pored filters. Working with sterile and nonsterile liquids, Prof. Erdey finds that differences exist in filtration effect and grain size of the precipitates due to micro-organisms in the nonsterile solution. Polymer Analysis. With the development of instruments that measure endothermie and exothermic activity with temperature changes of as little as 0.2° C , differential thermal analysis of polymers yields quantitative data on physical and chemical structure. John Mitchell, Jr., of E. I. du Pont de Xemours said that both preand post-melting behavior can be followed in a single run. DTA use has been extended in polymer analysis to measurements of freezing, melting, and boiling points; pre-melting crystalline transitions and glass transitions; collection of data for calculating heat and entropy of fusion and degree of crystallinity; and to follow thermal and oxidative degradation, polymerization, and curing reactions. Activation Analysis. Dr. W. W. Meinke of the University of Michigan covered basic principles and requirements of activation analysis, and reviewed the progress of the technique during recent years. After summarizing the development of small and portable nuclear particle generators, he cited areas of possible major development. These include such techniques as fast neutron activation, resonance neutron activation, prompt gamma analysis, and neutron emission. Chronopotentiometry. Various types of electrodes are available for use in chronopotentiometry said Dr. Donald G. Davis, Louisiana State University in New Orleans, in describing advances in this field. Key to accurate chronopotentiometric work is the design and construction of the electrodes. Under ideal conditions, an accuracy of ± 0.3% can be obtained.
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VOL. 34, NO. 3, MARCH 1962 ·
53 A
