Laboratory Heating Bath Using Fluidized Solids Milton Manes and David G. Chalmers
Pittsburgh Chemical Company Pittsburgh, Pennsylvania
LETTERS
To the Editor: I n his letter published in THIS JOURNAL, 37, 540 (1960), Professor Keighton of Swarthmore College crit,icized the omission of that institution from the list of liberal arts colleges whose faculty had published articles abstracted in Chemical Abstracts [See THIS JOURNAL, 37,316 (1960) 1. I state again that my classification was based on the designations in the 9th edition of the "College Blue Book." The omission of an institution which includes a school of engineering seems consist,ent,. The standing of any such professional school would be jeopardized by failure to publish in recognized scientific journals. Very seldom is the same true of liberal arts colleges. Kot only is it often possible for professional schools to secure funds for research, hut they often employ faculty members who give their full time to that activity. Again, such a condition is seldom encountered in liberal arts colleges. I regret that the adoption of this criterion may have resulted in the omission of worthy institutions. Their omission did not, imply the lack of productivity in research.
The laboratory heating bath described herein combines the high temperature limit of the traditional sand bath with the good heat t,ransfer and temperature uniformity of fluidized beds. The bath used in our laboratory (to heat a 2-ft. vertical reaction tube) consists of a nichrome-wrapped borosilicate glass tube, with a coarse fritted disc sealed near the bottom to contain the sand. Laboratory air enters the bottom inlet tube and passes through the fritted glass di~trihut~or, fluidizing the sand. loor example, 20 X 40 mesh sand is fluidized in a 2-in. 0.d. tube (about 30 in. in lengt,h) with air a t about 20 l/min. Smoother operation was observed using 80 X 200 mesh silica gel. At 300°C, and an air flow rate of 6 l/min, a temperature variation of *2'C was observed from a point 1 in. above the distributor plate to the top of a 10-in. bed. Further refinement in technique should probably give smaller temperature 1%riation through the usable bed length. The highest temperature sought has been 455°C; undoubtedly one can get - Bolo,iolr Tubs much higher temperatures with this sort of . system. There was some tendency for solids to - Nlhl"rot,". ild.." blow out of the bed, which was corrected by a glass wool plug. None of the specifica- i-;~ mom hi,lsd O1ess Om,,h*, tions or limits given here are critical. The system is recommended for its ---L o ~ m t o , " A,, simplicity and its easy
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To the Editor. A recent article by Ricket.ts in THIS JOURNAL, 37, 311 (1960), discussed an experimental approach to qualitative analysis as an exercise in deductive reasoning. We have used a similar approarh as a way of doing qualitative analysis in our terminal chemist,ry course. Students are assigned six cations and two sets of test reagents. The cations are chosen so that the separations involved will illustrate basic principles of chemical equilibria. The primary t,est reagents are used on separate 0.5 ml portions of each cat,ion. Where precipitates form, secondary tests are carried out on separate portions of the precipitates. Students devise and use analytical schemes based on their own test result,~. This approach teaches a great deal of chemistry and keeps student interest high.
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Journol o f Chemical Education
To the Editor:
I was very interested to read t,he note on Fehling's test by Daniels, Rush, and Bauer in your JOURNAL recently, 37, 205 (1960). I have spent a great deal of time trying to convince st,udents that this is not a specific test for aldehydes. Usually they do not believe me. When it is "in the book," the printed word carries great conviction. I would point out, t,hough, that Tollens reagent is not an "infallible test" for aldehydes as stated by Daniels, el al. Fructose is one ketone which certainly reacts with Tollens reagent, and I helieve t,hat all a-hydroxyketones do.
