STANDARDIZATION of CHEMICAL ENGINEERING LETTER SYMBOLS J . II. Perry and T. H. C h i i t o n , E. I. du Poiit de Yeinour3 Cy C , o r n p a r i ? , I I I C ., W i l m u i g t o t i , D e l . ; .J. K. Callaham, C h e m i c a l Engineering, New York, N. T.; 0. i.Hougen, Lni\eriity of Wisrorlsin, \Iadison, W i s . ; W. €1. hIc;idams, \Iassachusetts Institute of Technology, Cambridge, 11a-b.; W. L. \IcCabe, Carnegie Institute of Twhnology, Pittsburgh. Pa.: F. J . Van intwerpen. Chemicnl Engirtwring Progress. \ e w lark, Y. I . I
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N THE facing page is a tabulation of the letter ~ytiibri1.-
covering t h e concepts most geiierally employed in unit operations. This list is approved by the American Institute of Chemical Engineers and has been adopted as a n American standard by dmerican Standards Association (;is-& Z10.12--1946). T h e phenomenal growth of cheniical engineering in the pa-t twenty t o thirty years has led t o the development, of a large and complex vocabulary of terms used in unit operations and auxiliary operations. A natural tendency has existed for pioneers in certa.in fields to create a vocabulary for their specialty that frequently conflicted with terms used in other fields of chemical engineering, or in nonchemical fields where such terms as entropy, free energy, mass, force, and activity were in common use. T h e practical advantage of attempting t o reconcile these different groups of symbols has long been recognized. I n 1932 an official start at, development of a uniform list’ of symbol< w a ma,de ~ with t h e establishment of a committee of the American Institute of Chemical Engineers t o investigate t h e subject and t o wconimend desired usage. This committee made good progrv-h toward &mdardization, and in 1938 (6) published a tentative list of syniboh, which was revised and republished in 194-1 ( 8 ) . Somenclature in other branches of engineering had been a major concern of the American Standards Association since .January 1926, when the Sectional Committee on Letter Symhols and Abbreviations for Science and Engineering (Committee Z10) was appointed. Sectional Committee Z10 now consists of wpresentatives of thirty-seven national societies, associations, and governmental departments ( 5 ) . A.S.A. had not concerned itself t o any extent with t h e nomenclature in t h e particular field of chemical engineering, although i t had made progress in issuing niany other standard lists; among those of particular interest t o cheniical and heat engineers are t h e lists for mechanics ( 3 ) ,hydraulics (a), and thermodynamics ( 4 ) . In July 1943 Sanford A . Mo.ss, vice chairmen oi Sectional Coniniittee Z10, suggested t h a t a subcommittee, composed of the same personnel as t h e A.1.Ch.E. committee, be appointed with the goal of developing from t h e A.1.Ch.E. list of chemical engineering symbols, then in the final stages of development, a list that could be approved by A.S.A. as an Anierican standard for chemical engineering. This committee was constituted a s suggested, n-ith J. H. Perry as chairman, a,nd a revised list \vas submitted in Sovember 1944 t o the members of Sectional Comniittee 210 for letter ballot vote. This vote was favorable and was folloxved by a vote of approval by t h e five sponsor bodiea of A.S.A. (American Association for the Advancement of Science, American Institute of Electrical Engineers, American Society of Civil Engineers, American Society for Engineering Education, and .imericnii So-
nit.[)l’OSE!d it:iIldar.ti icvar for de..ig:riation as an America.ri gi\cii Septcnibcr 26, 1046: ( 5 ) . Thc puhlislird ytandarcl iiivludc- niaterial t h a t does not’conform in all ri~;.ljrrtsto other hnirrir:m standard pamphlets in that, t h e unit- :mil tlieir ai)lirevi&tion>a r r i,rconiniendations of the A.I. C1i.E. and do not coristitute :I part of the preierit, Ameririln stand: i d . T h e import,a’nt differences are a> follow: The pre3ent subc>oniniitteeha? inFihted 011 the use of periods, whereas the staridaid for wieiitific :mtl engineering terms ( 1 ) recommends their omisiioii. T h r rlniit har in-te:$tl of “per” ;uid ,‘lh, sq. in,’’instead of “psi.“ :LWal>o cmployed in the list recxcinunended by A.1.Ch.E. The hasis for these differencesfrom the previous American stkndai,ds is discussed in the March 1947 issue of Chemical Engineering Progress ( 7 ) . Recommended ahbreviatione for names of the principal units are given on the facing page, follow-ing t h e symbols. The rvork of arriving a t this qtandardlist included a survey of the piwtices employed by the leading publications, textbooks, and research institutions. This involved t h e resolution of >uch conRids as Rere found t o exist in the practice prevailing a t that time, nt t h e best usage. In scope and the outcome is belie ueed in mathematical equathis list is limited t o lett tions and expreisions, include standardization of names and definitions of the concepts represented. It does not extend t o the field covered by the h r 6 ~ 1 c . 4CHr,:vx(..kL ~ SOCIETY Committee on S o m e n c h t u r e , Spelling, and Pronunciation, which deals with the naming of chmiical compounds and such matters. Chemical symbols-that is, the symbols for ele mathematical symbols and do not come under t h So other lists of chemical engineering letter symbols, to our knowledge, have h e m published or officially proposed by any other organization up t o the preseiit time. The future plans of t h e committee in con~iectionwith letter .*ynihols for chemical engineering include R revisim or expansion of this list where the further >tudies of the committee and suggestions from the chemical engineering profession +howt h a t additions or changes are desirable. h further goal is the general use of the standard. T h e value of this 1i;t in simplifying the nomenclature problem will be directly related tu the extent to which each chemical engineer makes (‘onscious use of it. The mere publication of t h e list is only the start in the evolution of a standard; it is hoped t h a t sugge*tii)n~ for it3 iniprovpnient \rill be the nini of c r r r y c.11emic:il enginrrr.. LITER.ITURE CITEI)
(1) Am. Sfaridnrds. 210.1-1941 (19411. (2) I b i d . . 210.2-1942 (1942’1. (3) I b i d . , 210.3-1942 (1942). (4) I b i d . , 210.4-1943 (1943). ( 5 ) I b i d . , ZlO.12- 1946 (19461. ( G ) Badger, TT. L.. Chilton, T. H., Xe\\-inaii. -1, B., and .McA1daliLs, W.H., Trans. A m . Inat. Chem. Enors.. 3 4 , No. 1, 93-100 (1938). ( 7 ) Perry, J. H., Chem. Eng. Progress, 43, X o , 3 , 20 (1947). ( 8 ) Perry, J. H., Callaham, J. R., Chiltou, T. H., Hougen, 0 . .%., SlcAdams. TV. €I., McCabe, IT. L., and Van Antwerpen, F.J., Trans. A m . I n s f . Chem. Eugrs., 40, 90.2, 251-68 (1944). 1 Members ol the .Iiiieriran In-titute of Chemical Engineers’ Coninlittee on Standard Bysteni of Symbols and Somenclature Covering Unit Operations of Chemical Engineering, and Subcommittee S a . 12 on Letter Symbols for Cheniical Engineering of the Sectional Coininittee on Letter Symbols and Abbreviations for Rcienre arid Enerneering of the American Standards As-
soriation.
438
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