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 Front Cover
 Editors' corner
 Changing attitudes to reactor...
 Speaking out
 The chemical engineering approach...
 The integrity of chemical...
 Index for volume 1 (1965-1966)
 Back Cover














Chemical engineering education
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Title: Chemical engineering education
Alternate Title: CEE
Abbreviated Title: Chem. eng. educ.
Physical Description: v. : ill. ; 22-28 cm.
Language: English
Creator: American Society for Engineering Education -- Chemical Engineering Division
Publisher: Chemical Engineering Division, American Society for Engineering Education
Publication Date: June 1966
Frequency: quarterly[1962-]
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Citation/Reference: Chemical abstracts
Additional Physical Form: Also issued online.
Dates or Sequential Designation: 1960-June 1964 ; v. 1, no. 1 (Oct. 1965)-
Numbering Peculiarities: Publication suspended briefly: issue designated v. 1, no. 4 (June 1966) published Nov. 1967.
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General Note: Place of publication varies: Rochester, N.Y., 1965-1967; Gainesville, Fla., 1968-
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Table of Contents
    Front Cover
        Page i
        Page ii
    Editors' corner
        Page iii
        Page iv
    Changing attitudes to reactor design
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
    Speaking out
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
    The chemical engineering approach to entropy
        Page 70
        Page 71
    The integrity of chemical engineering
        Page 72
    Index for volume 1 (1965-1966)
        Page 73
    Back Cover
        Page 74
Full Text







FJN/E 1966M
JUN/E 1966A


CHANGING ATTITUDES
TO REACTOR DESIGN























chemical engineering

texts from Prentice-Hall


New for 1968...
INTRODUCTION TO FLUID MECHANICS by
Stephen Whitaker, University of California
at Davis. Provides an exceptionally thor-
ough treatment of the macroscopic (or
integral) momentum and mechanical energy
equations. February 1968, approx. 480 pp.,
$12.00

MATHEMATICAL METHODS IN CHEMICAL
ENGINEERING: MATRICES AND THEIR AP-
PLICATION by Neal R. Amundson, Univer-
sity of Minnesota. Outlines the elementary
theory of matrices discussing eigenvalue
problems, Hamilton-Cayley's theorem, and
systems of linear differential equations and
algebraic equations. 1966, 270 pp., $12.50

FOUNDATIONS OF OPTIMIZATION, by
Douglass J. Wilde, Stanford University and







For approval copies, write: box 903

PRENTICE-HALL


Charles S. Beightler, University of Texas.
Covers both the direct and indirect optimi-
zation techniques; extends the new non-
linear technique of geometric programming
to functions with negative signs and re-
versed inequalities. 1967, 480 pp., $12.95

KINETICS OF CHEMICAL PROCESSES by
Michel Boudart, Stanford University. Ex-
plains the kinetic analysis of elementary
steps, single reactions, and reaction net-
works for chemists interested in reactivity
and chemical engineers interested in re-
actors. April 1968, approx. 220 pp., $7.50


Englewood Cliffs, New Jersey 07632









0#EM/sffw






Contents for Volume 1, No. 4, June '66



55 Changing Attitudes To
Reactor Design

0. Levenspiel


70 The Chemical Engineering
Approach To Entropy

J. L. Throne


72 The Integrity of
Chemical Engineering

J. M. Douglas
and S. A. Miller


DEPARTMENTS


iii Editors' Corner


63 Speaking Out


R. G. Thorpe


EDITORS' I a

Chemical engineering curricula today face the
sternest confrontation of their entire history, a
challenge from inside the world of engineering
itself that amounts to questioning their raison
d'etre. Yet if the discipline of chemical engineer-
ing is reality and if the chemical process industry
is not illusion, there should be no doubt about
the reasonable purpose of chemical engineering
education. The core of that purpose is three-
kerneled: to prepare its graduates at all levels
to solve the engineering problems of chemical
processing, from research to marketing; to pro-
vide clear educational leadership in chemical en-
gineering in both academic and industrial spheres;
and to share strongly the technical leadership
of chemical engineering. The central kernel is, of
course, the first.
A not inconsiderable piece of the student's
equipment with which his chemical engineering
education should outfit him is attitude. He must
be conditioned to seek creative solutions to com-
plex, real-world problems. He must be able to
look at whole systems and not merely the com-
ponents thereof. He must be stimulated to sus-
tain a lifetime of continued learning. And he
must be aware of his field, recognize its power,
and sense the satisfaction it can yield to its
practitioners. Indeed, perhaps the most signifi-
cant burden laid upon late-twentieth-century fac-
ulties of chemical engineering is one of attitude.
We who teach must impress our undergraduate
and graduate students with the imperative of
continued scholarship and the reward that goes
with it. We must find ways to encourage disci-
plined originality. Above all, we must reflect
the genuine excitement of the real-life engineer-
ing problem. Without such inspiration, our stu-
dents can be expected to view the world of chem-
ical engineering toward which their college ex-
perience should direct them with mild interest
at best, and possibly with distaste. The persistent
maintenance of infectiously zestful attitude is a
demand of inestimable importance that we edu-
cators cannot evade.


ENGINEERING


b0ULAATION


The official journal of the


Chemical Engineering Division, American Society for Engineering Education


Editor Shelby A. Miller
Consulting Editor Albert H. Cooper
Assistant Editor John W. Bartlett
Publications Committee of CED
L. Bryce Andersen Chairman
Charles E. Littlejohn
E. P. Bartkus
James H. Weber
Executive Committee of CED
Chairman John B. West
Chairman-elect J. A. Bergantz
Secretary-Treasurer William H. Honstead
Elected Committeemen J. T. Banchero
W. H. Corcoran
Past Chairman George Burnet


CHEMICAL ENGINEERING EDUCATION is pub-
lished four times during the academic year
by the Chemical Engineering Division, Ameri-
can Society of Education. Publication months:
October, January, April, June. Publication
and editorial offices: 201 Gavett Hall, Uni-
versity of Rochester, Rochester, N. Y. 14627.
Title registered U. S. Patent Office.
Subscription rates: To Chemical Engineering
Division members, $3.00 per year; to non-
members in the Western Hemisphere, $4.00
per year; to non-members'outside the West-
ern Hemisphere, $5.00 per year; single issue
price, $1.50. Advertising rates quoted upon
request.


JUNE 1966


CHIEMICAL






THE AMERICAN SOCIETY FOR ENGINEERING EDUCATION


FOURTH ANNUAL

CHEMICAL ENGINEERING DIVISION

LECTURESHIP AWARD

to

Dr. Octave Levenspiel







SHE CHEMICAL ENGINEERING Division Lectureship
Award of the American Society for Engineering
Education is an annual award of $1000 to a distinguished
engineering educator for outstanding achievement in funda-
mental chemical engineering theory or practice. It is spon-
sored by the 3-M Company.
The recipient of the Fourth Annual Award, presented
on June 22, 1966, was Octave Levenspiel, Professor of
Chemical Engineering at Illinois Tnstitute of Technology,
who responded with an address on "Changing Attitudes to
Reactor Design." Previous award winners and the subjects
of their lectures were:
1965, Leon Lapidus, Princeton University
"Aspects of Modern Control Theory and
Application"
1964, C. R. Wilke, University of California (Berkeley)
"Mass Transfer in Turbulent Flow"
1963, A. B. Metzner, University of Delaware
"Non-Newtonian Fluids"


CHEM ENG ED








Changing Attitudes

TO REACTOR DESIGN


Octave Levenspiel
Professor of Chemical Engineering
Illinois Institute of Technology, Chicago, Illinois

Exciting things are happening today in
the field loosely covered by the terms
chemical technology, reactor design, and
kinetics, for, without fanfare, study re-
ports, or discussion in ASEE or in AIChE,
a new way of looking at this subject was
recently introduced. The new view may be
characterized by the phrase Chemical Re-
action Engineering, and its friendly recep-
tion by the profession is causing a remark-
able change in our approach to and our
teaching of chemical technology.
I should like to discuss this new develop-
ment, to sketch its strategy as opposed to
the traditional approach, to give a few ex-
amples to illustrate what I mean, to show
how it has affected our pattern of educa-
tion, and finally to consider what I feel is
its place in the main line evolution of our
profession.
In the traditional approach, we engineers
were more concerned with the peculiar and


unique features of this or that reacting
system than with the similarities and com-
mon characteristics among such systems.
It is true that the unique features make
for the success of a particular process. It
is also true that what is useful for the pro-
cesses of tomorrow are the analogies and
generalizations which we are able to extract
from the technology of today. Thus for
predictive and design purposes we need
generalizations; in the past, however, we
have emphasized the particular and the
unique.
In the U.S. of the forties we saw the
first break with this philosophy. The gen-
eral approach was brought forward; how-
ever, it was soon channelled, narrowed, and
dominated by the problems and interests
of the oil industry. Hence there was an
overwhelming emphasis on catalytic re-
actions and a rather unhealthy preoccupa-
tion with developing models to account for
their kinetics. Little wonder that this sub-
ject was known and is still known as applied
kinetics, chemical engineering kinetics, or
just kinetics, despite the fact that finding


JUNE 1966







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the rate of reaction is only one phase in the
over-all problem of scale-up and proper
reactor design.
In the late fifties a bolder attempt at
generalization was started in Europe. To
emphasize its concern with the over-all
problem it was termed Chemical Reaction
Engineering or CRE for short. As the name
suggests, we are here concerned with the
"engineering" of chemical reactions, or
their efficient exploitation. The philosophy,
then, is to seek common factors to link
processes and to develop broad methods of
attack for problems, and this is done with
the conviction that these methods can be
used as a basis for design in all areas of
application, whether it be in polymer pro-
cessing, industrial metallurgy, pharmaceu-
tical manufacture, foods, biological pro-
cesses, high-temperature reactions, or any
other operation - in fact wherever a new
material or chemical species is to be pro-
duced economically on a commercial scale.
In a nutshell the concern of CRE is shown
in Figure 1. Thus we engineers must deter-
mine how to treat a feed stream so as to
obtain most economically a most desirable
product stream. More specifically we must
decide what temperature, pressure, and
contacting pattern to use, and in general
this decision requires knowledge of the
stoichiometry, thermodynamics and kine-
tics of the systems.
It is convenient to classify reacting sys-
tems according to the phases participating
in the reaction. As shown in Figure 2 the
broad division is between homogeneous and
heterogeneous systems. In the former, one
fluid phase alone moves through the reactor


and only chemical kinetic factors influence
the rate. In the latter classification, we may
have to deal with additional problems aris-
ing as a direct consequence of the hetero-
geneity of the system, such as phase equili-
brium, mass transfer from phase to phase
or from phase to interface, and contacting
pattern of the phases. As may be expected,
heterogeneous systems represent a more
complex situation.
Next we see that homogeneous systems
may be divided into systems where only
one reaction occurs and into systems where
two or more reactions occur simultaneously.
The reason for this split is that different
questions are pertinent in these two situa-
tions. With one reaction all we ask is to
maximize conversion with a most economi-
cal reactor arrangement; with multiple
reactions we ask how (by what tempera-
ture, pressure, and contacting pattern) to
promote the formation of the desired
product and depress the formation of all
other undesired materials. The primary
concern is not the same in the two cases.
And so it is with heterogeneous systems,
where we have (in what I consider to be
the order of complexity) solid-catalyzed
gas-phase reactions, non-catalyzed fluid-
solid reactions (reduction of metal oxides,
burning of coal), fluid-fluid systems (ab-
sorption with reaction), and finally the
catch-all et cetera classification which in-
cludes all other multiphase systems. These
systems can be horribly messy to treat, and
in the interest of simplicity I shall avoid
them in this paper, even though they in-
clude many processes of great industrial
importance.
CHEM ENG ED


Homosemeous


mu ltiple|
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i ermo cre ion s
Fig. 2 - Classification of Reacting Systems





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JUNE 1966







The line at the bottom of Figure 2 shows
the usual stages in our control of reacting
systems all the way from initial studies on
thermodynamics and stoichiometry to a
search for optimum operation.
Our ability to handle problems is quite
different in the different classifications. For
example in homogeneous single-reaction
systems we are at the stage of selecting
optimum set-ups. In catalytic systems we
would be just about as far along if it were
not for the obstinate problem of represent-
ing and properly accounting for the kine-
tics of the reaction. With fluid-fluid sys-
tems our difficulties are everywhere: how
to represent the rate usefully, how to ac-
count for movement of reacting species in
the flowing phases, and in general how to
predict the extent of reaction given all
kinetic and equilibrium information. This
means that except for special cases we have
trouble trying to develop a design equation
for this classification. And so it is with the
other classifications shown in Figure 2; in
each there are particular difficulties to be
overcome.
Let me next offer three examples of re-
cent research activities in CRE. They must
be brief for this review to conform to rea-


sonable length. Nevertheless I hope that
they will provide a feeling for the sort of
thing that is going on.
The first example concerns the search for
an optimum set-up for the single catalylic
reaction whose thermodynamics and stoi-
chiometry are known, and let us restrict
ourselves to adiabatic operations in packed
beds. Now there are many possible ways of
running such a reaction - for example,
single-stage operations in one packed bed
reactor, multistage packed-bed operations
with interstate heat transfer, operations
with recycle of fluid between stages or with
bypassing of certain stages with fresh feed.
And for every set-up we can choose the
temperature of fluid entering the various
stages. With all these factors at our con-
trol, are we to make a computer search of
every possibility that comes to mind, or
are there methods which give us a feel for
the situation and allow us to reject quickly
many of the alternatives while retaining
those few which are promising? Since I
favor the latter approach let me outline a
graphical method which does just that.
Figure 3 shows the design equations for
the flow patterns of interest: the ideals of
plug flow and backmix flow and the inter-


CHEM ENG ED






mediate of recycle flow. It should be noted
that plug and backmix flows represent the
extremes of recycle flow when the recycle
ratio m becomes zero and infinite, respec-
tively. These equations indicate that the
four quantities, V (size of reactor), FAO
(feed rate of reactant A), -rA (rate of
reaction), and XA (conversion of reaction)
*


.-U1

0~I
-c


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are all interrelated, and knowing any three
of these quantities gives the fourth. The
sketches in Figure 3 are a graphical repre-
sentation of these equations for any ar-
bitary kinetics and the shaded areas are a
measure of the size of reactor needed for a
given duty. These expressions are quite
basic to CRE.


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JUNE 1967


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Figure 4 is the temperature-conversion
graph for typical exothermic and endo-
thermic reactions when starting with a
given feed. Shown in this figure are the
equilibrium curves obtained from ther-
modynamic considerations and typical re-
action paths starting with feed at tempera-
ture To, both for isothermal and adiabatic
operations. In the succeeding figures we


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shall build on this plot. I shall discuss only
the exothermic situation, but I include in
the figures the corresponding endothermic
reaction for the reader who wishes to pur-
sue that case on his own. The logic of the
two situations is somewhat similar.
Now to Figure 5: the dotted lines show
the locus of constant reaction rate, and this
general shape again is typical of all re-


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CHEM ENG ED







actions. Next, to minimize the size of re-
actor we want to choose the temperature
where the rate is maximum for that com-
position. The heavy line in this figure shows
the progression of temperatures which
satisfy this condition. Comparing with
Figure 4 we see that the slope of this opti-
mum line is opposite that for adiabatic
operations.
Because of the opposite slopes the way


all


to approach this optimum with plug flow
units is shown in Figure 6. Abiabatic stages
with intercooling are required. It is appar-
ent that intercooling simply shifts the
operating line horizontally to the left on
this graph.
Since it is impractical to use a large
number of stages, we may start by examin-
ing one-stage, two-stage, and then three-
stage operations. Figure 7 illustrates how


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JUNE 1966 61


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to find the minimum size of a two-stage
plug-flow unit to achieve a given conversion
XA,. The procedure is a one dimensional
trial-and-error where To alone is guessed.
Points a and c are found by the integral
given in the figure and point b has the same
rate as point a. Figures 8 and 9 sketch
analogous plots for recycle and for backmix
flow.
Again we ask if we must search all these


possibilities. Figure 10 indicates that this
is not necessary and that the key to the
proper contacting is given by the slope of
the adiabatic operating line. For the shal-
low slope of case a the rate of reaction is
extremely low at low conversions; hence we
should avoid operating in this range of con-
ditions. This immediately suggests that we
use backmix flow or recycle flow with a high
(continued on page 64)
CHEM ENG ED


U -


1'







R. G. Thorpe
Associate Professor of Chemical Engineering SPEAKING
Cornell University, Ithaca, New York


About-The Industry-University Interface

The classical conception of an interface, bounded
by several high resistance films and across which
mass and energy are transported under the in-
fluence of a driving force, has undoubtedly been
of more value in the solution of real problems
than any other concept one could name. Engineers
have always been singularly perceptive, if not
ruthless, in the adaptation of engineering ter-
minology to the description of human behavior.
It is not surprising then, to find "interface" being
used ir a particularly appropriate sense to de-
scribe the transfer of intellectual capacity between
groups which have quite different responsibilities
and interests. No empty verbalism this, for the
use carries with it the connotation that a re-
sistance to the transfer process does in fact exist.
I have returned to the academic cloister from a
most interesting and exciting sabbatic leave dur-
ing the 1965-66 academic year as a full-time en-
gineering consultant in the Engineering Tech-
nology and Services Branch of Monsanto's new
Central Engineering Department. I functioned
during the entire period directly with Monsanto
professionals in the solution of short-term prob-
lems and in the development of new technology
for long-term application. I now can see the pro-
cess industry-engineering college interface in de-
tail. The resistance on the industrial side is mini-
mal, but it is certain that the academic side re-
sistance is much too high for the single reason
that there appears to be much more concern in
the engineering colleges with advancing science
than with making the advances of science useful.
Clearly, there has been serious abrogation of re-
sponsibility by the colleges in the teaching of
analysis, synthesis, and design to meet modern
day demands - both at the undergraduate and
more seriously, at the Ph.D. level.
In the broad spectrum of engineering activity,
research has rightly been the pivot between prac-
tice and theory. Massive infusion of the colleges
with government contract research funds over a
period of several academic generations has
brought us to the point where the design naivete
of the instructor is producing students who are
design deprivates. Undergraduate students, in
general, are not being properly prepared to cope
with the very real and extremely complex en-
gineering design problems of today, and if the
present trend toward greater acceptance of the
non-experimental or "paper" thesis continues, the
engineering Ph.D. degree is in danger of becoming
an anachronism. Development of acceptable de-
sign competence in the student is an enormously
difficult task in comparison to the development of
research and theoretical competence. Even if the
engineering professor did not exist in a design

JUNE 1966


Immediately upon receipt of the B.Ch.E.
degree from Rensselaer, Raymond G.
Thorpe was ordered to active duty in the
U. S. Navy and served for four wartime
years. After the war had ended and he had
received his discharge, he pursued and
earned the M.Ch.E. degree at Cornell. He
joined Monsanto's Plastics Division, but
ultimately was drawn back to Cornell where
he has remained for over ten years.
A year of academic leave spent consult-
ing with Monsanto's Central Engineering
Department crystallized thoughts about the
relationship between engineering academe
and industry that Professor Thorpe had
been forming for some years. His observa-
tions were first published in the Monsanto
Technical Review, whose permission to re-
print them here CHEM ENG ED gratefully
acknowledges.



and technology void, the task would still be
difficult - and expensive. The industrial sabbatic
leave is one mechanism by which the engineering
professor may, it would seem, acquire the neces-
sary insight and skill for design teaching. All
too often, however, the young engineering pro-
fessor is merely transplanted from his own limited
academic research surroundings to a broad-based
industrial research environment. He gains in re-
search experience, fulfills both his academic and
industrial objectives, and returns to the campus.
His research-conscious academic administrators
are satisfied, but his students continue to remain
design cripples.
Monsanto engineering management believes
that technological upgrading of the young en-
gineering professor is not only necessary, but pos-
sible. What is required is that the professor be
temporarily absorbed into an engineering organi-
zation and permitted to function as a permanent
employee without restriction. Monsanto does not
subscribe to the concept of the prolonged guided
tour, but feels that mutual maximum benefit can
only occur if complete professional interaction
takes place in a climate in which the professor is
not only permitted free access to company per-
sonnel and technology, but most importantly he is
exposed to real economics and encouraged to
make a genuine contribution in decision making
processes. It is assumed that the professor, from
a new vantage point comparable to that of the
process designer, may reach certain inescapable
conclusions with regard to the limitation of the
purely theoretical approach and the true worth

(continued on page 69)







(continued from page 62)
recycle rate. On the other hand plug flow
is quite satisfactory for the steep slope of
case b. The numerical values shown on this
slide represent a heat of reaction of 30 Kcal.
So, simply by making this type of graph we
can tell what class of contacting schemes to
examine and what class to reject.
Other alternative arrangements can also
be considered, for example the cold-shot
cooling of Figure 11. This arrangement


-I


eliminates all the interstate heat ex-
changers; however it is only practical to use
this scheme under the conditions shown in
the figure.
Only a detailed cost study of exchangers,
catalyst, pumping, and the like will tell
which set-up is best in a specific situation;
however, I like this graphical procedure be-
cause it is rapid and simple to use, it is
general, and it is easily extended to non-
abiabatic and to homogeneous reactions. It


h 0


CHEM ENG ED






also gives a visualization, a feel, for what
is going on. I can't help thinking that its
role in reactor design is somewhat like that
of the McCabe-Thiele method in distilla-
tion.
But enough. Let us look at another area
where a search for generalizations is going
on. This concerns multiple reactions and
the question of product distribution.
Suppose we have a feed consisting of the


two dichloro compounds shown on the left
side of Figure 12 and we want to know how
to contact this stream with chlorine so as
to maximize the formation of the desired
trichloro compound. Should we use counter-
current contacting, concurrent contacting,
a vigorously agitated vat through which
chlorine is bubbled, or some other arrange-
ment? The direct way of answering this
question is to evaluate the five rate con-


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JUNE 1966





stants and then to solve the design equa-
tions for the various contacting patterns. It
would be very nice, however, if we had some
general rules allowing us to find the best
contacting pattern, not only for the reaction
shown in Figure 12 but for other reactions
as well, without going through the detailed
calculations, or better still, without even


knowing the values of the rate constants.
Such rules would be a useful guide and a
great timesaver.
A number of such rules have indeed been
proposed to date. Some have been proved,
while others are still conjectures. Let me
present a few of them.
Rule 1. For reactions in parallel, for ex-


a.


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CHEM ENG ED





ample A , the concentration level
of materials is the key to proper control
of product distribution: a high concen-
tration of a component favors the re-
action of higher order with respect to
that component, a low concentration
favors the reaction of lower order.
This rule is easy to prove for parallel re-
actions of all kinds including catalytic and
autocatalytic.
Rule 2. For reactions in series, say
A --e R --* S --- T, keeping the composi-
tion homogeneous, thus not allowing
material of different composition to mix,
will allow a maximum amount of any
intermediate to be formed.
This rule has also been proved in general
for any stoichiometry and reaction kinetics
and for any intermediate in the reacting
chain.
Rule 3. Multiple reactions can be looked
upon as a combination of their constitu-


ent series and parallel reactions, as far
as product distribution is concerned. For
example, the consecutive competitive re-
action scheme
A + B--R
R + B---S
can be looked upon as the sum of
A -*R --S and B S
This rule is useful and allows us to break
down complex reaction schemes into their
building blocks, from which the optimum
contacting pattern can easily be found.
Rule 4. With respect to product distribu-
tion every non-continuous contacting set-
up has its steady-state continuous-flow
analog and vice versa.
This rule suggests, for example, that if you
can produce a polymer with a specific mo-
lecular weight distribution in batch opera-
tions then you should be able to design a


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Cl

("" C1

,CI





Cl
0-


cI


CA

( Cl
)A


/X\DesireArn ranierial


+Cl



+CI3<


Co.

.DC8 1?eactor No ucbs


Fig. 12 - Multiple-Reaction System

JUNE 1966 67


C.1

C cl
CI
C1






continuous process which will give the same
quality product. Also beer, traditionally
batch-prepared, should be produceable con-
tinuously*. I suggest this rule with some
hesitation because it has occasioned rather
antagonistic responses, with counterex-
amples quoted from the literature. In fact,
none of the counterexamples have held up.
Thus, the rule is still open to question -
it has yet to be proved or disproved.
Rule 5. For a given set of reactions,
optimum contacting is independent of
the value of the rate constants.
This rule certainly holds for some of the
simpler reaction schemes, such as those
indicated in Rules 1, 2, and 3. It can be
shown by counterexample, however, that it
does not hold for all reaction schemes. My
opinion is that it holds if reactants enter
in separate feed streams and if their in-
troduction can be controlled, thus
A
" Reactor -> Product
B
but that it does not hold if the reactants
enter or are present in the reactor in a
fixed ratio which we are not able to control,
say if they enter in one stream
(A + B ) -! Reactor -4 Product
Rule 6. The steady-state optimum can
never be surpassed by unsteady-state
operations.
This is an interesting rule because recently
a number of papers have appeared suggest-
ing that unsteady state operations can raise
conversions and improve product distribu-
tion. All right then, in terms of general
classes of reacting systems what are the
limitations to this rule? Is it applicable to
homogeneous systems? To those with mass-
transfer-controlled kinetics? This is what
we need to know.
I could suggest others, but I think that
these six are enough to indicate the sort
of thing we are looking for. Actually we
are just beginning timidly to probe this
area, uncertain even of the questions to be
asked, never mind the answers. What we
need is our own modem day Euclid for
this area of CRE.
The examples cited have been intended
to demonstrate that the concern and em-
phasis in CRE is quite different from the
*It is being so produced. Ed.


approaches used in the past. Also, with all
the discussion in educational circles about
what constitutes proper research, I cannot
escape the conclusion that this type of
activity, this search for generality which is
useful for design and prediction, is indeed
engineering research in the proper sense of
the term.
Now to engineering education: here we
must ask how best to prepare students for
prediction and design for the problems of
tomorrow. Well, the basis of all experience
has shown that generalizations and uni-
versals are our best bet, not the details and
particulars of this or that phenomenon or
process. Generalizations constitute teach-
able knowledge, whereas the teaching of
facts that stand alone and outside of any
general conceptual framework is simply the
passing on of today's art. In fact, I may
go as far as to say that until a general point
of view is taken a subject cannot be taught
effectively.
To show that CRE does constitute such
teachable knowledge let us see what hap-
pened to the educational pattern after
CRE appeared on the scene. First of all
the first congress on CRE, where its pro-
gram was first spelled out, was held in 1957.
The 1962 ASEE survey of under-graduate
chemical engineering education in the US
gave these figures:
In 1957 18.5% of schools taught "Kinetics"
In 1961 53.2% of schools taught "Kinetics"
Professor Thatcher, who prepared this re-
port, considered this large jump to be the
most significant shift in the chemical en-
gineering curriculum in this period. Why
the increase? Is it a coincidence that not
long after the CRE approach was intro-
duced this subject - which had always
been important - all of a, sudden became
teachable? I'm convinced that it is no
coincidence. And if you compare the sub-
ject matter - before and after - in these
courses I'm confident that you too will say
that the CRE approach was largely respon-
sible for this shift.
As of today my guess is that the 53%
figure has risen to over 80%. This is a re-
markable development especially in view of
the fact, as I mentioned earlier, that it has
taken place without major discussion in
ASEE or AIChE.
CtIEM ENG ED






Finally I'd like to say a few words about
CRE and the main line evolution of the
profession. Early in this century the unit
operations approach was the unifying prin-
ciple which brought order to the study of
the physical operations of chemical tech-
nology, and it became the focal point about
which chemical engineering as a profession
achieved its identity, flourished, and grew.
Now, fifty years later, in the midst of much


Octave Levenspiel was born in 1926 in
Shanghai, China, and grew to manhood
there. He came to the United States in
1946, became a citizen
in 1958, is now married
and has three children.
He attended a German
elementary school, Brit-
ish secondary school and
French University (Uni-
versite l'Aurore) all in
Shanghai. Dr. Leven-
spiel received his B.S.
degree in chemistry in
1947 from the University
of California at Berkeley and his M.S. and
Ph.D. degrees in chemical engineering in
1949 and 1952 from Oregon State University.
Except for one year in research at Uni-
versity of California (1951-52), Dr. Leven-
spiel has been continuously in engineering
education. He taught at Oregon State Uni-
versity (1952-54), Bucknell University


(continued from page 63)
of his own academic research. The student will
inherit a long overdue legacy if administration in
the engineering colleges will recognize that the
intangible non-research activity so necessary for
analysis, synthesis, and design is not only aca-
demically legitimate, but important.
Many industrial managers hold the view that
the market for highly theoretical and research
trained engineering Ph.D.'s in narrow specialty
areas is rapidly becoming saturated. Progressive
graduate schools might very well either: 1, con-
sider adoption of a requirement that a portion
of the engineering doctoral candidates demon-


questioning in the profession about identity
and purpose, I see the promise of a similar
but broader unification, this time encom-
passing the chemical operations and with
CRE as its vehicle. Such is the role in our
ever-changing profession which I envision
for CRE, an approach whose name and
program were clearly spelled out a short
nine years ago. Only time will tell whether
we will shape CRE to fulfill this promise.


(1954-58) and Illinois Institute of Tech-
nology (1958 to the present), where he is
now Professor of Chemical Engineering. In
1963-64 he spent a year at Cambridge Uni-
versity as a National Science Foundation
Senior Post-doctoral Fellow.
In research and scholarly activities his
interests have centered about the use of
knowledge and the development of the gen-
eral approach for prediction and design. In
this line he has published articles on heat
transfer, fluidization, the design of chemical
reactors and flow patterns of fluids in ves-
sels. He has written a review on the last
named subject in "Advances in Chemical
Engineering", Vol. IV. In 1962 he wrote
"Chemical Reaction Engineering" to in-
troduce students to the method of design of
chemical reactors.
Dr. Levenspiel is a Professional Engineer
(State of Oregon) and has strong interests
in the philosophy and history of science,
and in statistics.


C


state an acceptable degree of competence in de-
sign, or 2, adopt curricula which will produce
broadly trained design professionals at the ad-
vanced degree level who are able to utilize
modem computational facilities to the fullest ex-
tent. Training of our young people cannot be
done by professors who are themselves design
illiterates.
Solutions to the problem of design instruction
will not fall out easily. We do, however, have an
effective way of using a new dimension in in-
dustry-university cooperation to scaledown the
problem.


P-I
(f-I


JUNE 1966







THE CHEMICAL ENGINEERING

APPROACH TO ENTROPY

Views of A Non-Thermodynamicist


James L. Throne
Assistant Professor of Chemical Engineering
Ohio University, Athens, Ohio


In a recent article (2), Bates sets forth some
"canonical statements" in an attempt to clarify
some of the irrational concepts and misleading
labels which have evolved with thermodynamics,
probably beginning with Black and the concept
of caloriess" (5). I wish to take issue not only
with Bates' approach to the healing of thermo-
dynamics, but with the entire philosophy of
teaching thermodynamics on the undergraduate-
first year graduate level. In this paper, I would
like to present what might be called a "non-
thermodynamicist" viewpoint to the problems of
teaching thermodynamics, my focal point being
the concept of entropy and its abuse in chemical
engineering. In a subsequent paper, I intend to
present a course outline for thermodynamics on,
say, a first year graduate level in chemical en-
gineering. Such a course has been taught success-
fully at Ohio University by non-thermodynami-
cists.
Forests and Trees
While Bates' arguments regarding misconcep-
tions and irrational nomenclature are well taken,
I am not convinced, first, that his introduction of
another set of nomenclature (regardless of its
rationality) is "first aid," and second, that even
if adoption of a standard set of symbols, de-
finitions, axioms, canonical statements, and what
have you, does take place (highly improbable,
when, for example, Tribus (1) introduces; through
information theory, concepts such as "temper"),
that this type of first aid will not result in direct
application to thermodynamics of the old saw,
"the operation was successful, but the patient
died."
I think that the dying patient, which I prefer
to call mechanical thermostatics (bowing to Tri-
bus' careful definitions here), needs radical sur-
gery, transfusions, and miracle drugs rather than
simple first aid. Perhaps the time has come for
the engineer who utilizes thermodynamics (in its
true sense, i.e., transport of heat, mass, and
momentum) in his work with physical and chemi-
cal phenomena (and here it must be understood
that I am referring to a much greater scope of
problems than those outlined by Bird, Stewart,
and Lightfoot (3)) to render advice and, if neces-
sary, to step in and perform the necessary sur-
gery himself. It may well be that those who now
apply first aid may see only single trees where
entire forests (mostly unexplored) lie waiting.


Philosophy and Thermodynamic Concepts
As is well known, there are two major ways of
approaching the developments of the major cor-
ner-stones of thermodynamics: through classical
or macroscopic developments and through "statis-
tical" or molecular developments. Both paths or-
iginate in physics and both require the person
following the development to make some form of
idealizing assumption. While I will have more to
say on this point in the subsequent paper, I want
to point out two recent important changes in
emphasis, one in each approach. In classical
thermodynamics, much work is being carried out
in "moleculeless" continuum mechanical thermo-
statics. While we seldom use this title, the de-
velopment of the energy equation explicitly de-
pends .upon this approach. In statistical thermo-
dynamics, Tribus' work and that of others dealing
with the development of a thermodynamics which
relies on information theory alone must be con-
sidered as a novel way of developing the same
principles one can obtain from "classical" (as
opposed to quantum) statistical thermophysics.
Undergraduate chemical engineering thermo-
dynamics courses are apparently so crowded now
(too many trees?), that aside from isolated ex-
perimental attempts (1) to introduce statistical
concepts, only the macroscopic approach is
emphasized.
Since we are dealing here only with under-
graduate thermodynamics, and since we must
recognize that thermodynamics is truly a building
block in the over-all concept of chemical engineer-
ing process and product design (or if you prefer,
systems and materials engineering), the pragmatic
philosophy must control the way in which we
present the three laws of thermodynamics and
their applications to real engineering problems.
Let me point out that, unlike Bates, I believe
that the first law of thermodynamics is the
"canonical statement" of temperature, the second,
of energy, and the third, of entropy. My position,
incidently, places me directly in the path of cross-
fire from the mechanicists who choose work and
power for the second and third laws and the
thermodynamicists who choose internal energy and
reversibility. It is not true, in my opinion that the
concept of entropy is more abstract than that of
energy, which in turn, is more abstract than that
of temperature. All concepts are abstract, if one
follows the Platonic philosophy; as a result, if we
are to use these concepts in any pragmatic (and
hence, engineering) way, we must make approxi-
mations to them. The student thinks he knows
what temperature is; he makes a "heat" balance
and thus has some connection, on paper or by

CHEM ENG ED






relation to some physical process such as heat
transfer, with the engineer's idea of conservation
of energy. However, what makes entropy mys-
terious (and thus, to the student at least, "more
abstract") is not the abstract concept, but our in-
ability to measure it with a meter!

What Good is Entropy?
To this question I am tempted to answer
"none," at least as entropy is presently taught
to undergraduate chemical engineers. If we deal
solely with the macroscopic mechanical thermo-
static developments, the classical development of
the concept is through Kelvin refrigerators or
Clausius (Carnot) heat engines, via the TS
versus PV diagrams, to the second law relating
a new variable, called entropy, to a measure of
reversible heat and temperature. The next step
is to rush into irreversible systems, to "prove"
that entropy in any conservative system must
either remain constant or increase with time.
Siedel (6) at one time collected some 25 state-
ments said to define entropy. At this point, rein-
forcement of the concept is needed (again because
we can't measure entropy) and in desperation
and with trepidation, the thermodynamicist dips
into statistical thermodynamics and extracts the
statement that entropy is a measure of the dis-
order of the system. Thereby he escapes cross-
examination either because the student is too
confused to ask for clarification or because no
real use is made of the pseudo-concept anyway.
Now I wish to raise two questions:
1. Why, if statistical thermodynamics is
to be referred to at all, must it be emascu-
lated only to support an archaic approach to
the ideas of teaching entropy?
2. Why is it necessary to teach mechanical
thermostatics to chemical engineers at all?
Carnot engines and Kelvin refrigerators are
great devices for making simple heat balances,
but certainly more realistic examples like
fuel cells, air liquefaction, and fresh water
recovery are more vital. The tired answer to
this is, of course, that the subject has been
presented this way for years, so why rock the
boat?
Boat-rocking notwithstanding, I would now pro-
pose the pragmatic approach to the concept of
entropy, leaning heavily on the recent work of
Coleman (4). Rather than 1) wasting time and
increasing confusion by introducing statistical
thermodynamics and 2) spinning wheels playing
with cycles and reversibility-irreversibility, I sug-
gest that the engineer's approximation to the con-
cept of entropy be put to work. From classical
thermodynamics we can determine whether a pro-
cess is reversible or irreversible, but we have no
idea of the rate at which a process is approaching
an equilibrium state (if ever), or the rate at
which conservative (reversible) energy is being
converted into dissipative (irreversible) energy.
At the risk of sounding like an "Onsagarist," I
propose that entropy be used not as a measure

JUNE 1966


of the reversibility of a system, but as a measure
of conversion of 'recoverable energy into nonre-
coverable or dissipative energy. Furthermore, that
the pragmatic approach to the utilization of
entropy be not in the calculation of the conversion
from stored energy to energy in motion, but rather
in the determination of the time rate of dissipa-
tion of energy in the form of heat. This means
that we are not restricted to Bates' PV versus TS
diagrams, but can now consider interactions be-
tween forces and fluxes (in a general way, or if
preferred, in the linear Onsagar Law way).
Entropy considerations will tell us not .only what
the system will or will not do but will enable us to
obtain a measure of the rate of energy dissipation.
To the student who has suffered through in-
numerable PV versus TS reversible-irreversible
problems and lectures, this "moleculeless con-
tinuum mechanical thermodynamics" approach
appears as an oasis in a desert of sand and
bleached bones of archaic thermodynamicists.

Conclusion
If I seem unkind to present approaches to the
teaching of thermodynamics, it is because my own
experiences as a student are healing very slowly.
Thermodynamics, or classical mechanical thermo-
statics, needs more than first aid. It is dying, and
unless non-thermodynamicists recognize the mal-
ady as malignant consumption and act quickly,
the do-gooders with their adhesive tape will short-
ly embalm the still-warm body.
I have tried to give an example of an entirely
pragmatic approach to a very simple concept,
entropy, and, more importantly, an illustration
with regard to the direct engineering application
of this concept to modern chemical engineering.
This approach would almost certainly allow
Gibbs to rest quietly - and I doubt that he is
resting quietly now.
It is admitted that no mention has been made,
either by Bates or me, of chemical thermostatics.
For my part, I support the philosophies of Gibbs
and Denbigh. Additional comments will be forth-
coming.

REFERENCES
1. Balch, C., University of Toledo, personal com-
munication, 1967.
2. Bates, H. T., Chem. Eng. Ed., 1, 37-43, (1966).
3. Bird, R. B., Stewart, W. E., and Lightfoot, E.
N., "Transport Phenomena," John Wiley, New
York, 1960.
4. Coleman, B. D., and Noll, W., Arch. Rational
Mech. Anal., 4, 97-128, (1960).
5. Roller, D., The Early Development of the
Concepts of Temperature and Heat: "The
Rise and Decline of the Caloric Theory," Har-
vard University Press, Cambridge, Mass.,
1955.
6. Siedel, B., University of Delaware, personal
communication, 1963.
7. Tribus, M., "Thermostatics and Thermo-
dynamics," D. Van Nostrand, Princeton, N. J.,
1961.








The Integrity of Chemical Engineering


J. M. Douglas
Associate Professor of
Chemical Engineering


S. A. Miller
Professor of
Chemical Engineering


University of Rochester, Rochester, N. Y.


Chemical engineering is a chemistry-and-physics
based discipline. Chemical equilibria and kinetics
share equal importance with physical equilibria
and transport rates. The conservation statements
about chemical systems are as significant as those
about physical ones. Furthermore, the processing
that accompanies chemical reactions in the manu-
facturing setting depends heavily on diffusive
transport of molecular matter, an aspect of
physical chemistry exploited predominantly by
the chemical engineer. In this kind of physical
operation there has developed peculiar identifica-
tion with the chemical engineering discipline.
By combining chemical (stoichiometry, thermo-
dynamics, kinetics), physico-chemical (diffusion,
phase transformation), and physical (heat trans-
fer, fluid mechanics, strength of solids) principles
under the constraints of practical economics,
chemical engineering has produced processes of
great complexity, carried out in plants that are
often enormous (ten million gallons of product
per day) and costly (hundreds of millions of
dollars). Chemical engineers are responsible for
the entire plant and process-their conception,
development, design, and economic operation -
every component of which must operate properly
with respect to all the others if success is to result.
This is true systems engineering.
The history and present status of engineering
and the engineering industries demonstrate that
there is a distinct need and proper place for the
peculiar educational experience that a chemical
engineering curriculum affords, and for the pro-
duct of that education. Chemical engineering
problems are characterized, indeed, by a degree of
complication greater than those usually identified
with the other traditional engineering fields. The
evolution of our discipline has brought with it
methods of attacking such problems, and concepts
of exceptional power and wide usefulness. A con-
sequence is that chemical engineers, essential to
the process industry, are in demand in a variety
of other environments, industrial and extra-
industrial. One of their great assets is their
ability to work unusually effectively with repre-
sentatives of other disciplines in the solution of
problems of great scope and interdisciplinary
character.
Notwithstanding the success of past advances,
the techniques and insight provided by chemical


engineering are still evolving, and there is strong
reason to believe that contributions arising out of
them will be even greater in the future. Chemical
engineering originated from the consolidation of
the principles common to a number of previously
isolated use-centers: the paper industry, petro-
leum refining technology, acid manufacture, et
cetera. Its great strength derived from its capacity
to unify and establish bonds between these other-
wise diverse, discrete industries, and to provide
education and training that make the chemical
engineer effective in all of them. Today there
seems to be some tendency again to fragment the
field into use areas with new names but distinct
identities: environmental engineering, food en-
gineering, and the like. A competing tendency
would generalize certain of the subdisciplines
shared by several of the engineering fields into
new disciplines: thermal engineering, materials
science, and systems engineering are examples.
In both cases, the identification of interest centers
at which competence from a number of disci-
plines can converge for the attack of broad super-
problems is useful and salutary. But to suggest
that they should subordinate or supplant the
established discipline of chemical engineering is
to suggest the destruction of the burgeoning
promise of tremendous future contributions ori-
ginating in our field.
We submit that future society will benefit
most from the maintenance and continued evolu-
tionary development (at the most fundamental
level consistent with the definition of the field)
of an academic discipline erected on the subject
matter at the core of chemical engineering today.
Simultaneously, vigorous effort should be directed
to those developments at or near the diffuse
boundaries where other currently defined disci-
plines, basic and applied, and chemical engineer-
ing merge. We believe that such a frankly disci-
plinary approach optimizes the task of conserving
and extending the treasure of knowledge, under-
standing, and skill for which chemical engineering
has become a particular repository; of applying
that treasure to new creative goals in the world
of the process industry; and of sharing major
interdisciplinary challenge with others in a sig-
nificant effort which, in using without sacrificing
its contributing collaborators, is enduringly
synergistic.
CHEM ENG ED















h#EMJ I7




fe1 A7


INDEX FOR VOLUME 1 (1965-1966)


AUTHOR INDEX


SUBJECT INDEX


Abraham, W. H. ..--
Bates, H. T. ----.--
Berg, L. ---- - ......-
Burkhart, L. E. -----
Burnet, G. -------..--.-
Burr, A. A. ---- ....--
Chilton, T. H ........--
Christensen, J. J ......-
Douglas, J. M ---. ..-
Genereaux, R. P. ----
Griffith, D. E. ------
Hamielec, A. E. .---
Hubbard, R. M ---....-
Kenyon, R. L. ..----------
Kiser, K. M. ------..
Levenspiel, 0 --...--------.
Madonna, L. A. ----.---
Miller, S. A. -------
Murphy, G. -------
Pfeffer, R . ...---- ...
Schmidt, A. X. .....----
Snyder, J. R. ------.
Thorpe, R. G. -----.
Throne, J. L. ---...--
Wheelock, T. D. ..--
Willis, M. T....... ------
Wise, D. L. ------ ..-
Woods, D. R. ----.-
Yerazunis, S. ------. ...--.--


-------------.... 12,
------------------..........
---------------- .(1)


.....-----------------.-.-------
............................
............................











1
------.----------------------
----------------------------







1
. .... . . . . . ...... . .
---.----...........-----
-...----- -----.......






--1------------------------
............................
............................
............................

............................
............................
............................








----------------------------


--------------. 19,


Bifurcation ------.......------ ---------..... 1, 5, 3, 7
Career choice ----------...... .......---------------- 12
Chemical Engineering Division -- (1) iii, (1) iv


1
iv
7
9
14
72
27
1
52


Cooperative programs
Core curricula --..-
Curricula -
Design
Engineering science
Entropy -
Five-year programs
"Goals" Report ....---
Industry, relations with


...-------- ... 14
--- -----... 24
--- 1, 3, 5, 7, 14, 25
(3) iii, 19, 52, 55
-----....--. 24
-- ------- 70
--------- 14
------- - (2) iii
------- 9, 27, 63


10 Integrity of Chemical Engineering
15 Interdisciplinary programs ....-.
48 Job choice --------------
55 Laboratory demonstrations ......---
24 Multifurcation -------... ...--
72 Option, curricular ..-----
3 Overhead projector ----..... ------
13 Process control (book review)
13 Professional challenge ..-------
11 Professional practice ----....---
53 Reactor design ---- --------
70 Reactor design (book review) ---
5 Rensselaer program ---....--------...
16 Science-oriented curricula ---- .
24 Teaching aids ----------- ...
52 Teaching load -----.-------
7 Thrmodynamics -----------
Transport phenomena -------
Trouble-shooting ---..-------...
Unit operations --..--......--.....
Visual aids ...---- ..............-------------


--- 72
1, 24
- 12,44
---- 10
--... 1,3
1,3,5, 24
---.... 11
---- 30
---- 45
-- 9,44
-- .. 55
--- 48
... 7
3, 7, 24
- 10, 11
-. .... 13
_ 37, 70
---. 46
- ---- 19
- --- 46
--.... 10


JUNE 1967







CHEMICAL ENGINEERING EDUCATION
? / 201 Gavett Hall,
University of Rochester,
Rochester, N.Y. 14627.


November 17, 1967



Dear Subscriber:

No, there's nothing wrong with your mail
service. It is your editors who are responsible
for your receiving Volume 1, Number 4 of CHEMical
ENGineering EDucation in November, 1967, instead of
June, 1966. But although the masthead date shown
on this issue is technically correct, you may be
assured that the contents are contemporary. Copy
for all of the material that it carries except the
feature article was received within the last six
months -- some of it, notably advertising copy,
only a fortnight ago. And Professor Levenspiel's
fine paper is certainly as readable today as it
was in mid-66.

We are sorry for the delay. We hope that
you find the issue rewarding in spite of having to
wait for it so long.

The official publication of ASEE's Chemical
Engineering Division will come to you in the future
under new, extremely competent editorial leadership.
I know that bright days lie ahead for all of us readers
who are interested in chemical engineering education.
Meanwhile John Bartlett, Al Cooper, and I are grate-
ful for the privilege we've had to serve you and the
Division during an interim period in the life of
CHEMical ENGineering EDucation.

Sincerely yours,


S. A. Miller
Editor

SAM: sm




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