TRENDS Advances in corrosion science and engineering have made invaluable contributions to modern industry, but much remains to be learned and put to use. Assessing future needs o f those whose jobs involve the combatting of corrosion, H. H. Uhlig of MIT’s Department o f Metallurgy j n d s the expansion of three scient$% areas to be particularly necessary [J. Electrochem. SOC.,115, 108C (7968)1. Uhlig urges studies of: ( 7 ) ejectrode kinetics, (2) the nature of initially formed surface j l m s on metals, and (3) the way in which metals subject to a tensile stress interact with their environment. There is certainly no room for complacency when we cannot say with assurance whether thepassivejlm on stainless steels is a metal oxide or an adsorbed complex of oxygen and water. Uhlig’s remarks were given originally at the dedication of a graduate center for materials research at the University of Missouri in October 7967. On the same occasion he also suggested the establishment of a national institute for corrosion control for the coordination of corrosion research and to ensure its implementation.
Water vapor can be compressed to high densify at supercritical temperatures.
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The vapor pressure curve of a pure liquid ends at the critical point at which the liquid and gaseous phases become identical. By increasing the pressure at temperatures above the critical, liquid-like density of the gas can be attained without phase separation. For instance, at 500” C, the gas density increases from 0.01 g/cm3 at about 20 atm to 2.0 g/cm3 at 150,000 atm. Investigation os the chemical behavior of high-temperature water [Franck, E. U., Endeavour, 27 ( 7 0 1 ) ) 55 (1968)]in the pure state, as well as when serving as a solvent, throws interesting light on structural problems of 4ao 5oo boo polar fluids and on solvation phenomena. In addition, properties of the geochemically important “hydrothermal” solutions can be explained. (‘c)
procedure which solves component material-balance equations with a tridiagonal matrix algorithm. The unique feature of this procedure is that, in a mathematical sense, the equations are solved simultaneously. Therefore, the method can be used for all types of equilibrium stage processes according to T. F. Tomich, ESSOProduction Research Co., Houston, Tex., in a paper “ A hTew Simulation Method for Equilibrium Stage Processes” presented at the Second Joint AIChE-IIQPR meeting. Additionally, the use of Broyden (heat balances and summation equations) iteration ensures solutions which are both stable and more rapid than current techniques. A n exact solution for a 20-tray column with 20 components takes approximately 30 sec on an IBM 360165 computer. Design applications of the method may cover a variety of equilibrium-stage processes in the chemical and petroleum industries. Equilibrium stage operations may be simulated by a new general mathematical
Mechanical breakdown of solid polymers is capable of producing free radicals in
the polymer mass and so materially aids the initiation of block or graft copolymerization reactions. For some years it was assumed that the production of free radicals in polymers after grinding or milling was due to thermal degradation following the inevitable rise in temperature during mechanical working. Several investigators, most recently R. E. Eckert, T. R. Maykrantz, and R. J. Salloum of Purdue University [Polymer Letters, 6, 2 1 3 (7968)1, have, however, shown that free radicals are produced by fracture of the solid polymer and cleavage of the polymeric chain. The Purdue workers ball milled polystyrene in an atmosphere of nitric oxide, a free radical acceptor, and were able to verify that bonds were formed between the polymer and the NO, using a form of infrared spectroscopy. 4
INDUSTRIAL AND ENGINEERING CHEMISTRY
Backmixing in continuous flow systems is widely encountered, but it has recently
been pointed out by Professor A . Klinkenberg, now at the University of California, that some confusion is arising concerning the precise meaning of “backmixing” [Chem. Eng. Sci., 23, 92 (7968)l. Klinkenberg stresses that backmixing should involve movement backward past a $xed point or plane; other writers have started to use the term backmixing to describe any mechanism which results in a distribution of residence times for j u i d elements (i.e., any j o w other than p l u g j o w ) . This latter deJinition of backmixing is injnitely broader than Klinkenberg’s, and since it is being applied to describe systems when j o w velocity is locally both greater and less than the mean velocity, use of the preJix “back” is inappropriate and misleading. I n making this point, Professor Klinkenberg is performing a useful service similar to that of J . J. Carberry who emphasized the important diference between the terms “yield” and “conversion” in chemical reaction engineering in I€YEC, October 7966. Diffusivities in binary liquid metals can be measured by means of a concentration cell technique devised by J . B. Edwards, E. E. Hucke, and J . J.Martin at the University of Michigan [ J . Electrochem. Soc., 115, 488 (7968)]. The cell used for determination of the dz$usivities of metal A in an alloy, AB, of A with another metal B consists of an anode of pure A (sodium and potassium were studied at Michigan), a fused salt electrolyte containing A + cations impregnated in porous alumina, and a cathode containing the alloy A B (alloys with mercury, lead, and tin were used). By putting the M alloy in a capillary tube, dayusion of A through the alloy was assured of being the ratecontrolling step in the electrochemical process. A knowledge of the relationsha) between discharge current and quantity of metal transferred from anode to cathode, and of the relation between the equilibrium cell potential and cathode composition was needed in order for the electrical measurements taken to be converted into the j o w s and concentrations used in the appropriate solution of Fick’s second law.
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The heart as Q thermodynamic engine operates with an eflciency which is far greater
than that of any engine as yet built by man. The most remarkable and the most vital characteristic of the heart is its power of adabtation, of altering its activity, i.e., the amount of work it performs, according to the requirements of the body as a whole. J i m Steinbeck ( Wisconsin Engineer, Dee 7967, University o f Wisconsin) analyzes the mechanics of this adaptive ability. He has studied the mechanical process by which this work is done, calculated this work, calculated the total amount of energy required, and from these values arrived at ajigure denoting the eflciency of this most important thermodynamic engine. This jgure is not constant, but varies from a low of 72% to a high of 36y0in proportion to the work required. A new type of oxygen monitor has been developed by I . Bergman at the Safety in Mines Research Establishment in Shefleld, England [Nature, 218, 396 (7968)l.
The monitor uses as its working basis the fact that oxygen reduces the intensity of fluorescence given 08by a fluorescent material exposed to exciting radiation. Bergman has usedjuoranthene as the Jluorescent material, and his earlier devices involved bubbling oxygen-containing gas through a solution of JEuoranthene in cyclohexane. Although the presence of oxygen considerably diminished the intensity of Jluorescence in this crude arrangement, response time to changes in oxygen partial pressure were necessarily long. In the latest embodiment of the monitor, juoranthene dissolved in cyclohexane is absorbed in the pores of Vycor glass. The cyclohexane solvent is driven of, and the glass matrix allows both rapid response and the strong relationsha) between oxygen concentration and fluorescent intensity required for accurate measurements. VOL. 6 0
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