- _January, 1923
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
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Physical Chemistry in Industry By R. S. Tour UNIVERSITY OF CINCINNATI, CINCINNATI, OHIO
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HYSICAL CHEMISTRY, as the name implies, may be After Lavoisier, more orderly investigations were carried on considered as that branch of science lying in the great and far-reaching discoveries in chemistry followed. Dalton borderland of physics and chemistry where the prob- attempted to summarize much of the work that had been done lems of each become so interconnected that they cannot be before him and in his “New System of Chemical Philosophy,” separately studied. Pure chemistry as a science has to do published in 1811, he laid the foundation stones for our physchiefly with the composition and constituical chemistry or theoretical chemjstry. tion of substances and classifies matter in He brought forth an “Atomic Theory” terms of its component elements. The wherein he assumed that matter was comchemist may use specific physical properposed of “atoms,” of fixed characteristic ties or definite energy relations to distinweight, which were simple in the true guish compositions or constitutions, yet elements and complex in compounds. He these characteristics themselves are but the further stated that elements combine in means to an end. Physics, on the other fixed proportions, and formulated what we hand, is concerned especially with the propnow know as the “Law of Multiple Proerties or the energy relations of matter portions.” per se, and classifies matter in terms of its PHYSICAL CHEMISTRY OF TO-DAY characteristic properties. Thus both physics and chemistry are concerned with propThe present realm of physical chemistry, erties of matter and energy, and for more i. e., the theoretical chemistry of to-day, complete correlation or greater generalization, the problems arising must be studied may be considered as a still more recent from both the physical and the chemical development than indicated above. It standpoint. dates back perhaps no further than the It is obvious that these two basic last half of the 19th century, when the laws branches of natural science, physics and of thermodynamics were being established. It has been by the study of the relations of chemistry, must have a great common ground, and it is logical that this common energy and matter that many of the great Towles ground should have first been known as strides in physical chemistry have been R. S. TOUR physical chemistry. It is only here that accomplished and that many of our present really conclusive generalizations may be drawn, laws for- theories have been developed. The present physical chemismulated and resultant theories propounded. Thus, most of try may be considered as based on three distinct developments: our hypotheses and theories of chemistry and of chemical the application of thermodynamic reasoning to chemical action have been developed in the realm of physical chemistry. problems; the generalized extension of Avogadro’s hypotheThis has been the case to such an extent that physical chem- sis; and the rise of the theory of electrolytic dissociation. istry, principles of chemistry, and theoretical chemistry have These three developments incidentally typify the fundabecome of recent years practically synonymous. To quote mental requirements for a normally rapid growth of any Arrhenius: “The theoretical side of physical chemistry is science: exact reasoning, generalized hypotheses, and logical and will probably remain the dominant one; it is by this theory. peculiarity that it has exerted such a great influence upon the The requirements for the normal growth of a science, neighboring sciences, pure and applied, and on this ground exact reasoning, careful generalization, and logical theory, physical chemistry may be regarded as an excellent school of are also prerequisites to the successful application of the exact reasoning.” results of any scientific investigation outside of its own sphere. Since physical chemistry demands and fulfils these preTHEBEGINNING OF PHYSICAL CHEMISTRY It has been said that chemistry as a science began with requisites, it is in a large measure responsible for the applicaLavoisier in the latter part of the 18th century. It may tion of chemistry in the world to-day; and the world benefits further be said that Lavoisier was the first great exponent of by scientific investigation only in so far as such investigation physical chemistry. He insisted that the balance, an in- finds application. The individual investigator may, and strument for purely physical measurement, be used for generally does, derive his reward in a purely psychological chemical investigation and finally established the “law of medium of exchange, but the community upon which, in conservation of mass.” Previous to this time most of the some way or other, he must depend for his necessities must experimentation and research was disorderly and uncoordi- be paid many times over for the outlay. nated, although Boyle had pointed out in his “Sceptical The present status of human knowledge, and that is present Chymist” (1662) the unsatisfactory results of the prevailing civilization, is an evolution of the study of cause and effect. methods and the importance of the logical application of the When such study of related phenomena develops generalizaprinciples of experiment and deduction. Yet, as late as tions and laws from which in turn other phenomena may be 1775, Priestley, the discoverer of oxygen, writes: “More prophesied or explained, civilization has been given a most is owing to what we call chance-that is, philosophically valuable tool. This tool may or may not have an imspeaking, to the observation of events arising from unknown mediately apparent application to the needs of humanity, causes--than to any proper design or preconceived theory in but if it gives the scientist a better understanding of his this business.” science, or if it aids in the advancement of that science as such,
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INDU6XRIAL A N D ENGINEERING CHEMISTRY ;i
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it will lead indirectly to applications which are of benefit to the community.
THEAPPLICATION OF PHYSICAL CHEMISTRY The application of the sciences for the benefit of mankind is a true definition of engineering. The sciences are the tools of the engineer. The -value of physical chemistry as a n engineering tool is sometimes questioned. A few industrial executives still remain who complain that the “theoretical” man is not “practical.” As this statement is generally interpreted, it may apply in individual cases. Yet this cannot condemn the value of theory for practical application. Who can deny the value of the phase rule developed by thermodynamio reasoning and mathematics, in the fields of metallurgy or in the industrial operations of distillation or crystallization? Who will question the applicability of the laws of equilibria in reversible chemical reactions? Who doubts the importance of the theory of solutions? As any problerh arises in an industry, it may be attacked in one of two ways, either empirically or scientifically. The former method is that sometimes known as “practical.” -But, in general, even the so-oalled or self-styled “practical” man attempts a scientific mode of attack on his problem, As a rule, he will proceed according to some hypothesis or theory that he’has developed to fit the particular case in hand. How much better and how much more certain of success he would be if the hypothesis or theory were always based on exact reasoning and correct principles. The truly empirical method of attack, not based on theory or reason, depends for its sukcess on chance. Success may come quickly but the probability of success is generally remote. as into contactwith the chemical inthat there are to-day too many plants OPerating under conditions no less than archaic. I n these plants win be found the hard-and-fast rule, ‘
