TRENDS

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TRENDS

but it could utilize nearly 1 5 millzotc tom of the nation’s trashpile. Professor Cedric W . Richards, Department of Civil Enpinepi ing, Stanford University, Stanford, Calif. (Technol. Kev., Vol. 72, No. 4, Feb. l W 0 , !J 66) has a plan to recover andpurify glassjowder from urban incineration f o r U I P ur aggregate to replaLe the sand in aerated concrete. T h i s aerated concrete is a foamed cemented mixture that can be foiined into panels and short beams. I t can be sawed and fastened much the same as wood paneling, has good thermal insulating and jreproojing qualities, and is ideal for prefabricated construction. Concrete from glass may be as clear as mud,

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N e w valwes of the solubility parameters from vapor pressure data have been calculated by K . L. Hoy, Union Carbide Corp., South Charleston, W . V a . ( J . Paint Technol., Vol. 42, A ~ o541, . Feb. 197Q,p- 7G-118) from an expression derived from the relationship of Haggenmacher. Over 680 values of the solubility parameter were calculated and presented in tabular form. From the data obtained, it has been possible to expand the usefulness of Small’s Molecular Cohesion Constants. The chameleonic nature of associated molecules is discussed as a means of understanding some apparently anomalous physical phenomena.

are of frequent occurrence and are usually carried out in either ajixed orJuidized bed; however, little is known about the improved heat transfer rates to gas-solid mixtures produced by swirl j4ow promoters. B . B. Lodh, G. S. R. N . Murthy, and P. S. Murti, Indian Institute of Technology, Powai, Bombay 76, India (Brit. Chem. Eng., Vol. 15, No. 1, J a n . 1970, p j 73-75) describe an investigation of the e$ects of promoter geometry and particle properties, and give an equation for two-phase transfer coe8cients. They found that heat transfer and pressure drop for two-phase stwirlj’ow increase with increase in width of the promoter, gas velocity, loading ration, and decreasing pitch of the promoter, and that heat transfer rate is dependent more on heat capacity of the solid than its thermal conductivity. Reactions between gases and solids

G. C. A . Schult (Chim. Ind., 51, No. 12, Dec. 1969, pp 1307-1318) gives a survey of work on the oxidation of

What makes an oxidation catalyst er selective catalyst? 5/01.

o l & s over oxide catalysts. O n the basis of theories and experimental results from other groups, a mechanism for the oxidation, selective andlor nonselective, has been set up. Tliis comprises the allylic intermediate, the Mars- Van Krevelen theory of catalyst reduction and subsequent reoxidation by 0 2 . The active site is supposed to be an anion vacancy at the surface of the catalyst oxide. Five factors are postulated as important in deciding catalyst activity and selectivity.

by an X-ray defraction technique is described by R. C. Rossi, Aerospace Corp., Los Angeles, Calif., and R. M . Fulrath and D.W . Fuerstenau, University of Calif., Berkeley, Calif. (Ceram. Bull., Vol. 49, No. 3, March 1970,pp 289-292, 373). T h i s technique is especially useful becaure it gives not only the chemical composition of samples from the mixer before sinterinp, hut also the composition of the sintered material. B y determining the amount of reaction /irod?LcL produced in samples from the mixer, a sensitive mea.rure is obtained of the degree oJ,4mlicle --article contact in the mixture. I n this study, even though sample analysis indicated compositonal uniformity of the mix, spinel determination showed that maximum $article-particle contact was not attained. Quantitative analysis of the mixing of fine powders

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