TRENDS Steam distillation of aroma extracts from foods can be measurably improved by a new apparatus designed by A . A. Williams of the Uniuersity of Bristol Department of Agriculture and Horticulture. Steam distillation for these applications is limited by the low volatility of the aroma content, which comes ouer the top w i t h enough water to dissolve it or make it so dilute that subsequent recovery f r o m the distillate is dzjicult. Key to the apparatus’ efectiueness (Chem. Ind., Vol. 18, Oct. 1969, p 1510) i s the use of side arm in the receiver which drains the aqueous distillate into a supplementary receiver rather than back into the stillpot. Hence, the distillate is continually soluentextracted with the extracting solvent returning to the stilbot. Williams has used the method successfully on the uery delicate flavor components of strawberries and cider. Diffusion of water into high polymers may be determined by several methods. Ernst-Otto Schmatz and Horst Grundke, VEB Chemiefasercombinat, WilhelmPieck-Stadt (Faserforsch. Textiltech., Vol. 20, h T o . 8, 7969, pp 377-3232) present a gravimetric and manometric method especially designed for granulate samples. Experimental results given were obtained w i t h nylon 6 and polyethylene terephthalate between 70’ and 200°C. The vibrating viscometer has been applied to continuous viscosity measurement in stirred vessels. T h e principle used by E. Kleinschmidt, Herbol- Werke and HerbigHaarhaus A.G. (Paint Technol., Vol. 33, iVo. 9, Issue 382, 1969, pp 34-43) is that of a blade of magnetostrictive material vibrating at an ultrasonic frequency. T h e damping of the vibrating blade by a liquid depends on the viscosity of that liquid and is indicated on a chart recorder. Since the liquid in a stirred uessel is in a state of turbulent flow, the probe of the instrument has been given a new shape to prevent disturbances that may aject readings.
at circular cylinders in a transversejeld offlow has been made by W. Kriickels (Chem. Ing. Tech., Vol. 4 1 , No. 19, 1969, pp 7068-1076). T h e flowing medium is air; the substance to be transferred, ammonia, is absorbed on the surface of the bodies and chemically bound. Studies were made using circular cylinders of aarious diameters in j e l d s of transverse flow. T h e method enables local mass transfer numbers to be determined to within 5.470 while using relatively simple equ$ment. Photometric measurement of the local mass transfer
Laser pyrolysis apparatus for gas chromatography using a pulsed ruby laser was constructed and tested on a variety of samples by 0. F. Folmer, J r . , and Leo V . Azarraga, Continental Oil Co., Ponca City, Okla. ( J . Chromatog. Sci., Vol. 7, Nov. 1969,pp 665-670). For comparison, the samples were also pyrolyzed with a jilament pyrolyzer and with a tube-furnace pyrolyzer. T h e chromatograms obtained f r o m the laser apparatus generally show simple patterns and discriminate more ejectively between similar substances than f r o m either of the other approaches. Deliberate synthesis of new complex organic compounds is the latest job thrown at the computers, thanks to Dr. E. J . Corey ana’ Dr . W. Todd W i p k e of Haruard University (Sci. News, Vol. 96, Nov. 15, 1969, p 449). T h e molecule needed f o r a chemical job i s manually drawn with a special pen on an electrostatic tablet. An image then appears on a cathode ray tube connected to the computer. T h e computer has been programmed w i t h general rules governing chemical reactions. I t then works backward in stepwise sequence to come up with a succession of subelements that could lead to the desired molecule. 2
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
a sophisticated and expensive f o r m of food preservation, according to Arnold Spicer (Food Technol., Vol. 23, No. 70, Oct. 7969,pp 42-57). T h e two limiting factors are: (a> mass transfer (the transfer of water vapor from the ice front) and ( b ) heat transfer (transfer of heat to the ice front). T h e rate of mass transfer depends on the pressure gradieGt across the dry material which i s related to the drying rate and the structure of the dry layer. T h i s restriction on mass transfer imposes limits on heat transfer, as the supply of heat to the ice front has to be constantly changed to suit the available capacity for water vapor removed. Freeze drying has been and still i s
Heat transfer in flowing gaseous suspensions is dz$cult
to determine but methods habe been developed to enable designers to make more accurate predictions. Whenfine particles are added to a j o w i n g gas, the wall heat transfer coejicient can be considerably increased, and the prediction of this efect is often important for design purposes. R. G. Boothrogd, Dept. of Mechanical Engineering, Birmingham University, Birmingham, England (Chem. Process Eng., Vol. 50, No. 10, 1969, pp 108-7 1 4 ) reviews the dependence of wall heat transfer on p o w conditions, radiation, thermophoresis, and duct entrance efects, all of which are signiJcant factors. is reviewed i n the October 1969 (Vol. 50, NO. 10, pp 67- 702) issue of Chemical Process Engineering in seven articles. D. Noden, Pratchitt Bros. Ltd., Carlisle, England, reviews industrial dryers f or selection, sizing, and costs. W . Hauschild, Luwa AG, Zurich, Switzerland, describes thin f i l m evaporatorldryers and K . Masters, Niro Atomizer, Ltd., Copenhagen, Denmark, reviews spray drying of minerals. T h e other titles include rotary louvre dryers by G . C. Browner, spray drying of thixotropic pastes by M . Young and A. J . C. Ireland, turbotray dryers, coolers and calciners, and molecular sieve dryers. Drying as a unit operation
A n automatic program for finding the unit cell from powder data has been developed by J . W. Visser, Technisch Physische Dienst T N O - T H , Delft, T h e Netherlands ( J . Appl. Cryst., Vol. 2, Pt. 3, 1969, pp 89-94). T h e program jinds the constants of the reciprocal lattice frompowder data and the planes through the origin of the reciprocal lattice. After evaluating these, the program selectspairs of zones with a common row i n order to find reciprocal lattices which are then reduced in a simple way. Each solution is compared with the experimental data, and a jigure of merit i s calculated. T h e author points out that the program is limited by its dependence on the accuracy of the input data.
Get the computer system you want. Management failures, not mechanical failures, have caused many mismatches of computer systems and corporate needs. T h e computer has done a great deal for business, but unfortunately, it has done in a number of businessmen-especially i n the cases of new computer systems that are delivered later or do not work as expected. For these troubles, according to Roy M . Freed in the Nov.-Dec. 1 9 6 9 isshe of Haruard Business Review, management usually can blame no one but itself; it just has not insisted on the kinds of procurement policies and practices that have become standard for other major equipment purchases. Freed shows how a reasonable degree of top-management involvement i n contracting can substantially improve the chances of getting optimal performance from computer systems. VOL. 6 2
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