I&EC TRENDS TODAY
New clues to the free radical character of lignin come from electron spin resonance
(ESR) characterization of proposed structural models us. correlations with ESR characterization of lignin. C. Steelink, on leave from the University of Arizona, has shown from work at the U. S. Department of Agriculture Forest Products Laboratory that various lignin-containing products including whole wood contain free radicals. He concludes that lignins are in part comprised of a simple molecular structure derived from quinhydrone. Related research at the same laboratory yields conjrmatory evidence that both diphenyl ether and biphenyl linkages exist in lignin. This was established through experiments with enzymatic coupling of simple phenolic compounds, which also yielded evidence of monomeric phenols in lignin. A s the result of these new jindings, we are brought closer to decreased loss of lignin in chemical processing of wood and the possibility for more extensiue commercial use of lignin. Simulation of multimonomer polymerization has been successfully carried out for test formulation of multicomponent paint vehicles by Jerome A. Seiner of Pittsburgh Plate Glass Co. Using Price-ALfrey copolymer parameters, he has developed a computer program for accurate prediction of compositional distribution or degree of polymerization W i t h the use of the at any instant after reaction initiation for multimonomer systems. Seiner “Monomer Machine,’’ it is proved possible to obtain from a computer readout a semilog plot of weight per cent of polymer us. per cent conversion, the latter of which is a function of time. Shown to the right is one such plot with per cent conversion on the abscissa, this one for polymerization of an initial mixture of S5770 ethyl acrylate, 27.5y0 styrene, 2.5y0 meihacrylic acid, and 5.0% acrylamide. This technique is one of several manifestations of the transition of the traditional paint trade to a coating formulation science (see p . 52).
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Coupling of liquid-liquid extraction with chemical reaction is the subject of research in several quarters. Rigorous mathematical treatment of this coupling is impossible because chemical reaction is a scalar rate process and extraction is a uector rate process. Therefore design has only been based on empirical treatment of the process variables, and this can be complicated by the possibility of four dzyerent processes: dzfusion in each phase andlor reaction in each phase. T w o empirical correlations for particular cases of coupling extraction with chemical reaction have been developed recently, which we hope will help clarify the situation. A t Uniuersidad Nacional de L a Plata in L a Plata, Argentina, J . J . Ronco and J . C. Merchuk are studying the integration of kinetic equations expressing mass transfer with simultaneous chemical reactions for systems with transfer coeficients which vary depending o n where you are i n the system. Using concepts of “efective areas of transfer,’’ they have developed expressions linking volumetric reaction factors to technical Damkohler numbers (functions of dtyusion and mass transfer coejicients) , and hence have provided generalized representations of practical use for correction of the Van Krevelen-Hoftijzer diagram and dejinition of irrigation quality of packing. T. Corrigan of Ohio State University has been studying kinetics of extractive reactions to deteimine efect of extractive agents on chemical reaction kinetics, and on product distribution in parallel reactions; results of this study permit eualuation of the use o j liquid-liquid extraction to enhance product yield with such parallel reactions. VOL. 5 7
NO. 8
AUGUST 1965
7
Q=UAAT+E
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BARTLETT-SN0W - PAC1FIC
I&EC TRENDS
INDICATORS FOR TOMORROW
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Dropwise condensation on hydrophobic noble-metal surfaces has proved advantageous for distillation conversion of sea water as the result of development work by R. A. Erb and E. Thelen at the Franklin Institute under sponsorship of the U S . Ofice of Saline Water. T h i s work has led to the discovery that thin coatings of gold or silver on copper-alloy tubes can increase condensation rate per unit area and increase the overall heat transfer coejicients by 50 to 90%. This major step forward in heat transfer results from a long search for hydrophobic substrates to achieve dropwise condensation. Once-tried T e j o n coating proved nonideal because of its low thermal conductivity, although R. L. Hummel of the University of Toronto has reported ten- to one-hundred-fold increases in heat transfer coejicient with application of T e j o n spots on tubes; many investigators have tried organic and inorganic materials chemisorbed on metallic-tube surfaces. More recently, su&de and selenide jilms have been tried at Franklin Institute; but only very recently was the discovery made that unsuljided silver provides better dropwise condensation than suljided silver, and that gold displays similar properties. Nonwettability of noble-metal jilm is explained by lack of surface oxides present, and the weak bonding of water to the surface by dipole-induced, dipole and dispersion forces. Several approaches now being made at Franklin Institute seek to optimize performance per unit f i l m thickness and hence achieve more attractive economics.
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Roughness factor of powdered solids is measured by a new technique, developed bv Sidney Ross and Ian Wiltshire of Rensselaer Polytechnic Institute. N e w technique utilizes dgerence in adsorption of dgerent size gas molecules, a method traditionally used for porosity determinations for porous powders. After the total surface area of the powder is determined by gas adsorption, a nonvolatile material of relatively high molecular weight is adsorbed on the solid surface. Remeasurement by gas adsorption shows the degree to which the surface area i s decreased. T h i s decrease represents the jine-grained structure of the substrate denied to the gas by the presence of the larger molecules. A n example of the application of this technique is the measurement of roughness of graphitized carbon black, using ortho-tricresyl phosphate as the preadsorbate and argon as the surface-measuring adsorbate.
such as quasilinearization, dafferential approximation, and dynamic programming are being applied to fundamental problems of engineering and applied science by R. E. Bellman and colleagues at the Rand Corp. Using these new tools, they are attempting to unscramble experimental data. Another noteworthy application is the determination of the structure of mathematical models given random observations over a given period of time; this approach is distinct from the usual practice of predicting future model behavior after deJining the model for a given initial state. New mathematical techniques
Generalized method of predicting high-gradient mass and heat transfer has been suggested by W. E. Ranz and P. F. Dickson of the University of Minnesota. Their work, reported in this month’s I H E C Fundamentals Quarterly (pp. 345-531, was concerned with review of simultaneous transfer with large concentration and temperature gradients, variation in transport coejicients, convection caused by dzfusion, and boundary conditions. For transfer systems that warrant analysis, they recommend a three-step procedure involving mapping of boundary values, establishment of assumptions about the principal variables, and integral analysis to determine functional relationships. VOL. 5 7
NO. 0
AUGUST 1965
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