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cury the vapor pressure, Po, of the pure material which is adsorbed a t the temperature of the adsorbent T ; and scale D gives the equilibrium adsorbate pressure, P, from the adsorbent a t the same temperature. I n order to find - AF for a given adsorbate concentration and temperature, the equilibrium adsorbate pressure point on scale A is connected by a straight line to the vapor pressure of the pure material which is adsorbed corresponding t o that temperature. This line when extended will intersect the reference line, M . When the point of intersection is connected to the temperature in question, the straight line when extended will intersect scale A to give directly the value of the term A F .
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adsorption isotherms for a system when only one isotherm has been determined experimentally. For any irregular systems where the free energy changes with temperature, the range of utility may be narrowed; although usually it will be the entire range of commercial import8nce. This method of interpreting data is excellent in evaluating the suitability of a n adsorbent for the qualitative adsorption of a given vapor. It will not allow the evaluation of heats of adsorption with any considerable precision.
Foi usual engineering work the values of A F are not desired, but this nomogram allows the direct determination of values of equilibrium pressures, temperature, and concentrations outside of experimental range merely by using the - A F scale as a “pivot scale” and without any use of the free energy concept directly. Thus, if it is desired to find the pressure necessary to produce the same adsorption concentration at a different temperature, the value for - A F found as indicated above for a n experimental condition may be connected through the new temperature to give a new reference point on scale M . A new point on the reference line is thus obtained. When this new reference point is connected t o the value of the vapor pressure (scale C) corresponding to the new temperature, this line extended to scale D will show the equilibrium pressure necessary to give the desired adsorbate concentration at the new temperature. By this method, it is possible to evaluate for all systems obeying this basic assumption any given value of concentration and pressure at any desired temperature or, in fact, a full set of
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ACKNOWLEDGMENT
Thanks are due to Salvatore Silvis for his help with this manuscript. LITERATURE CITED
BerBnyi, S., 2. p h y s . Chem., 94, 628 (1920). Ibid., 105,55 (1923). Brunauer, S., “Adsorption of Gases and Vapors,” Princeton, Pliinceton University Press, 1945. Emmett, P. H., and Brunauer, S., J. Am. Chem. Soc., 57, 2732 (1935). Josefowitz, S., and Othmer, IND. ENG.CHEM., 40, 739 (1948). Ledoux, Edward, “Vapor Adsorption,” Brooklyn, N. Y . , Chemical Publishing CO., 1945. Othmer, D. F., and Sawyer, F. G., IND.ENO.CHEM..35, 1269 (1943). RWEIVEDSeptember 5, 1946. Presented in part before the Division of Induotrial and Engineering Chemistry a t the 110th Meeting of the AMERICAN CHEMICAL SOCIETY,Chicago, Ill.
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Indexing Abstracts C. L. BERNIER AND E. J. CRANE Ohio S t a t e University, Columbus, Ohio The permanent value of a set of abstracts depends largely on adequate indexes. Abstracts are not made up of definite, uniform, single units of information, and their classification in a published journal does not prevent information from becoming buried. The common alphabetically arranged subject index has thus far been the most effective key to such information.
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HE great bulk of rapidly accumulating chemical information has led t o the need for big annual and huge collective indexes, which present challenging problems in nomenclature, form, structure, and the effort for consistency, accuracy, and adequacy. Furthermore, modern mechanical devices such as machines operated by punched cards and still more recent developments with electronic devices have raised questions as to possible substitutes for indexes. Without denial of the possibility of mechanized assistance in dealing with chemical literature, which is being thoroughly investigated, i t seems fitting at this time t o provide information on the building and use of subject indexes. For general use, these are not likely to be supplanted. Chemical Abstracts publishes five different kinds of indexes, based on (1) author names, (2) subjects, (3) empirical formulas of compounds, (4)patent numbers, and (5) organic ring structures. This discussion is limited t o subject indexing. MAKING A SUBJECT INDEX
The story of the making of a n index entry for the subject indexes t o Chemical Abstracts may be interesting and. useful to index users. Inquiries indicate t h a t there is misunderstanding in this connection. Some think, for example, t h a t only titles are
indexed. More entries are made from the bodies of abstracts than from titles, and original papers are very frequently utilized in our index building. Perhaps a beginning should be made by a word or two about the vocabulary of the indexer. An index must be built of words, and the indexer is continuously confronted with nomenclature problems, not only those of chemistry, but also those of botany, bacteriology, engineering, and every other phase of science and technology in which chemistry plays a role. Chemistry is a growing science, and the indexer of a n abstract journal must frequently deal with nomenclature in its early stages when lack of standardization and even lack of full knowledge make for indefiniteness. It is on this account t h a t collective indexing presents so many tough problems. I n speaking of the vocabulary of the indexer, however, we are thinking not of the words which he must use as building stones, but of those which he must use in speaking of his profession. A good index is something more than a key and pointer. It is a sort of inanimate memory. The human memory and indexes seem similar in that both store information in such a way t h a t i t can be recovered upon demand. Indexes bring together like information and, with their cross references, help in the correlation of data. The whole picture of what is happening in the field covered by a n abstract journal can be gained in outline form from its indexes. An index can become a source of good nomenclature information. What is a subject? It is t h a t concerning which anything is said or done. It is not a word or a phrase. Too often so-called subject indexes are really just indexes of words. Words are but the tool of the indexer. They must be used in such a way as t o avoid scattering of references to like subjects, omissions, and
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and column reference v,-ith fraction a t the bottom as shown. The X indicates t o the printer that this card is to be part of a double indenture. The next operation is that of checking the card for correctness of column number, subject selected, and modification chosen. Alphabetizing is another operation and editing of the cards the final one before they are sent to the printer.
Figure 1.
Structure of Subject Index
mnecessary entries. A subject suitable for storage in a subject index can be anything known to man. For this reason, subject indexes are the most flexible and comprehensive of all kinds. The subject indexes to Chemical Abstracts have a definite and comparatively rigid structure. Figure 1 shows most oi this structure. The heading is in bold-face or black type. Below the heading are the modifications, so called because they modify the heading in much the same way that adjectives modify a noun. After each modification comes the column reference and fraction which, starting this year, is i letter rather than a number. The heading, modification, and column reference with its fraction constitute an index entry. The heading is not a subject; neither is the modification, nor are both together. A heading with its modification is simply a condensed guide to a subject or an aspect of a subject in the material indexed. Following this heading is a cross reference. Cross Seferences play a most important role in leading the index user from place to place in an index where information sought or related information may be found. A good index contains inany cross references. The various indentures, indicated in Figure 1, avoid repetition and thus save reading time.
For many of t'he entries in the Chemical Abstracts Subject Indexes, eight operations by eight different people are involved, with consequent opportunity to check both as to accuracy and judgment used: (1) marking page proof for indexing, (2) making. cards, (3) checking cards for references, (4) checking these for modification writing and subjects select,ed, ( 5 ) alphabetizing, the cards, (6) editing the assembled cards, (7) checking the references on proof, and (8) general proofreading. As most of these operations are done by chemists,. there is good opportunity to catch mistakes in judgment or execution. The editing of the assembled cards a t the end of an index period is much more of & task than might be expected. h group of alphabetized cards under one heading presents a different picture from that presented by a single card vihen it is made or checked. This editing for Chemical Abstracts is aided by an extensive system of invert'ed cross references (40,000 of them) to ensure that the correct cross, references are used, t o get like things together, and otherwise t'o,
The mechanics of indexing Chemical Abstracts is comparatively simple. The first operation is that of marking. This consists in underlining, checking, or writing in a word or phrase on the page of abstracts to be indexed, after study of the abstract. It is always done by a chemist. A marked page of Chemical Abstracts is shown in Figure 2. Each underlined word or word written in represents one entry in the subject index. The second operation is index card malting (Figure 3). Cards are used to facilitate alphabetizing and editing. The heading is put a t the top, the modification in the center, and the volume
Figure 2.
Page Marked for Subject Index
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provide careful correlation. Scattering of like information is one sf the greatest faults of a carelessly built subject index. The mechanics of indexing is, of Fourse, much less important than the philosophy of indexing, which controls not only the structure but also everything that goes into the index. Thus, the philosophy of indexing governs the selection of information.
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Ethylene
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I Figure 3.
Index Card
Figure 4 shows a short abstract. What information is to be selected from it to go into a subject index? Chemical Abstracts makes, as the basis for this selection, novelty and(or) emphasis. By “emphasis” Chemical Abstracts means significance as subject matter, even though the emphasis is light. That which has been studied or discussed, even incidentally, is indexed, but common solvents or reagents, well known starting materials, unimproved and commonly used apparatus, etc., are not indexed when they are incidentally treated in a paper; when they constitute the theme of the paper, they are indexed, of course. Novelty and emphasis are so interrelated that they should almost be mentioned in the same breath. In the abstract of Figure 4, the novelty lies in the experimentally determined relations between flame structure, composition, and rate of feed of gas, and in the claimed confirmation of a hypothesis of Clusius and others. The emphasis is given fairly well by the title, “Hydrogen diffusion and flame structure.” The composition of the gas mixtures used is also chemically significant, although not mentioned in the title. This abstract was indexed, as marked, a t Hydrogen, Diffusion, Flames, Oxygen, Carbon dioxide, and Methane. The novelty and emphasis reflected in the abstract are products of the labors of the author of the paper and are not under the control of the indexer nor of the user of the index. We like, a t times, to think of an abstract as resembling a relief map modeled in clay. The peaks on the map correspond to the novel or emphasized information of the abstract which, in turn, reflects the novel or emphasized information in the original paper. It is not.difficult to pick out the high peaks on either the map or the abstract. One has difficulty occasionally with the very minor peaks-in knowing whether or not to select them. &lost of these problems are solved by an attitbde of generosity; .“When in doubt, index” is the motto. However, an index can be harmed (cluttered up) by too many entries, just as it can be harmed by too few entries. The time of users is too valuable to ask them to follow unfruitful leads. Once the indexable information is selected, the next task is to fit it effectively into the pattern of the index. Thus, if the heading Density had been used before in the index, it would be unwise to start the heading Specific gravity. Headings preferablv consist of words most commonly used by chemists instead of synonyms or related words. I n this way, information is put where the majority of index users will look first. Some index headings, such as Density and Viscosity, are con-
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sidered general headings, suitable for entries on methods of measurement, relationships, and the like, but not for studies where specific values of density or viscosity are given. Thus, a study on the values for the density of mercury a t various temperatures would be indexed under Mercury but not under Density; whereas a study on methods for the determination of the density of mercury would be indexed both under Mercury and under Density, the latter entry being made because of possible application of the methods of measurement to other substances. This is another phase of fitting selected information into the pattern of the index. The different headings have definite and, occasionally, highly restricted meanings to the indexer. The sense in which the heading is used can be discovered by a glance a t the entries under it. Thus, Ceramic materials means, in an index to Chemical Abstracts, the clay and other raw materials, whereas Ceramic ware means the finished or partly finished ceramic products. Refractory materials means materials refractory to heat and not necessarily t o corrosion. Waterproof materials means materials resistant t o swelling, discoloration, destruction, and shrinking by water, as well as those merely resisting penetration by water. This process of fitting the selected information into the pattern of the index often takes more time than selecting the information, especially in the indexing of complicated chemical compounds. It is, in a sense, a process of classification; however, the index so produced is not a classified index in the sense of systematic clasnification. Thus, 2-butene is considered best entered under its own name rather than under Olelins, which, in turn, might be placed under Hydrocarbons. The consistent fitting of information into the index requires extensive knowledge of the index and makes the training of indexers a long process. The indexers for Chemical Abstracts have hundreds of guiding notes to help in this. If a new bit of information does not fit under one of the existing headings, a new heading is started, and once started, is rarely abandoned unless shown to be unsuitable or incorrect.
H dro en di&sion and flame structure. Hans Beh3--9( 1944) .-Clusius and re&&m-jten others ( C . A 36, 43TS8) explained the unusual combustion of H - 0 mixts. by rapid dxusion of H which causes the flamevont to become nonhomogeneous and to consist of a 5 no. of individual threaded flames. Expts. were made with lean H flames (H CO2 0 mixts.) confirming this hypothesis. Either a Metertype burner or a fritted-glass burner was used. Curves show the change in no. and size of ’the flame threads as a function of the H content and of the rate of feed. The H concn. varied from 0.15 to 0.25 stoichiometrically (ratio 0:CO? = 40:60). Photographs illustrate this thread-flame eEect. If CH, is mixed in with the gas, the flame appearance is w a p 6 B. J . C. van der Hoeven
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Figure 4.
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Typical Short Abstract
I n order more specifically t o designate the subject selected, the heading is usually followed by a modification. For example, “filtration of molten” is placed under the heading Sulfur. The structure of good modifications is fairly definite; the indexers have thousands of notes telling the salient points of modification writing for many of the headings in Chemical Abstracts. The most important word in a modification should come first when possible, and maximum clarity with a minimum of words should be sought. Every word bears so much weight that even tKe prepositions are chosen with care. Classification of entries under a heading is not usually sought, although a serious attempt is made to bring like things together. A few statistics on the subject indexes to Chemical Abstracts will help to give more background for the discussion of indexing which follows.
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The number of entries for Volume 40 is about 200,000. The number of headings in an annual index is, roughly,’40,000. There are approximately 675,000 words in the subject index to Volume 40; this represents about one fifth of the number of words in the abstracts. When one takes into consideration all the kinds of indexes issued by Chemical Abstracts, including the author indexes to the individual numbers and the collective indexes, it can be said t h a t for every thousand words published in the form of abstracts 650 words are now published in the form of indexes.
Chemical Abstracts has a “master file” of about 40,000 cross references from which perhaps 30,000 are selected for inclusion in an annual index.
It is best for indexers to specialize. Organic chemists deal with the organic sections, biochemists with the section on biological chemistry, and so on. At present, twelve workers put in a t least a part of their time on indexing subjects. TRAhSMISSION O F CHEMICAL INFORMATION
This Symposium on Technical Library Techniques is concerned, fundamentally, with the transmission of chemical information among chemists. Indexes constitute only one step, a n important one, in this transmission. Others are: observation of the experiment, recording as notes, collection of the notes into a paper, publication of the paper, abstracting (which may involve translation) and publication of the abstract, indexing of the abstract and publication of the index, searching of the index, and conversion of the words in the abstract or original paper into ideas. There is a good deal of variation in efficiency among these steps. Since all these steps are rarely held in mind, the efficiency of an index is sometimes overrated as a factor in the over-all transmission of information, but there is probably no more important single factor. It will be well to bear in mind all these steps when consideration is given to index substitutes or supplementing devices. An increasing amount of money is being set aside these days for scientific research. There is a tendency for those responsible for research grants to overlook the fact that publication of the results of research work is an important part of the whole undertakirig and t h a t adequate publication includes not only full original papers but also secondary publications. Efficiency all along the line is necessary for high over-all efficiency in transmission. Indexes or substitutes therefore cannot be counted on fully to correct inadequacies in other phases of information transmission. Chemical Abstracts is placing more and more emphasis on the preparation of abstracts complete from the indexing viewpoint and on the indexing of every bit of useful information. The number of papers and patents abstracted in 1936 was 62,763 and these abstracts occupied 8692 columns on the pages of the journal. I n 1946, the number abstracted was 38,753 and these occupied 7706 columns. This represents an expansion of 44%, in ten years, in size of abstract. The method of abstracting patents has been revised to give more chemical information. The indexing is being improved continuously. The number of index entries per abstract has increased from 2.9 in 1936 to about 4.2 in 1946. More than 400 entries were made for one recent abstract. Chemacal Abstracts has always made a good many more index entries than does the average journal for a given paper. The index user has been helped, especially in his struggles with chemical nomenclature as used in Chemical Abstracts, by the Introduction to Volume 39. This comprehensive description of nomenclature practice can be obtained separately as a reprint. Chemical Abstracts assisted in instituting the A.C.S. Photocopying Service which is helping bridge the gap between abstracts and original papers. A11 these things, and many others unmentioned, are aiding in getting chemical information from chemist to chemist more quickly and surely.
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THEORYO F INDEXING Let US look a t indexing from the viewpoint of both the indexcr and the index user. The subject indexer is concerned with the selection of novel and(or) emphasized subjects. The point of view of the author of a paper naturally has much to do with the t,rcrid of his study and with the points of emphasis in his result,s. This makes it seem somet’imes that the same subject matter had been indexed in entirely different ways. Here is an example: One author studies the kinetics of the reaction between sulfur dioxide and oxygen in a solution containing catalysts. His paper would be indexed under Sulfur dioxide, Oxygen, Reaction kinetics, Catalysts, and possibly Specific catalysts. Another author studies the removal of sulfur dioxide from air by passing it, through a solution containing the previously mentioned catalysts. This v-ould be indexed under Sulfur dioxide and Air, and possibly Catalysts. A third author studies the manufact’ure of sulfuric acid by passing a mixture of sulfur dioxide and air or oxygen through a solution containing the same catalysts. This would be indexed under Sulfuric acid and perhaps under Catalysts. ,4 fourth aut,hor studies the dktermination of hydrogen sulfide in air by burning it to sulfur dioxide, passing the sulfur dioxide with air through a solution containing the same catalysts, and titrating the sulfuric acid formed. This would be indexed under Hydrogen sulfide and Air. Thus, apparently the same subject, t,he reaction of sulfur dioxide wit,h oxygen in solutions containing catalysts, is indexed in entirely different ways because the indexing is controlled by the emphasis or viewpoint and purpose. At first thought, this difference in indexing of apparently the same reaction xeem.5 to point t o a grave defect in the policy of permitting viewpoint to control the index entries selected. This defect,, if it really existed, would make impracticable if not impossible a complete literature search on any subject, except by chance. Actually, there is no defect, for, in the example given, the react,ion between sulfur dioxide and oxygen was studied only by the first author; in the last three cases, it was tacitly assumed that the reaction was a n old one and so required no study. Had the last three authors also studied or emphasized the kinetics of a novel reaction between sulfur dioxide and oxygen, their papers would also have been indexed under Sulfur dioxide, Oxygen, and Reaction kinetics, as t,he first paper was. I n a very real sense the reaction in the first case wa,s different from t,he reaction in the last’ three. ,In t,he first case it was novel and st,udied; in the last three cases t,he reaction was well known and unemphasized. Thus, the difference in indexing is justified, for it would be highly undesirable to have an index send the user repeatedly to information already known. A4uthorssometimes fail to indicate clearly novel information, abstractors fail to abstract it, and indexers fail to index it. These failures, however, pose entirely different problems and are quite unrelated to the effects of the policy of indexing by emphasis or viewpoint,, except in so far as such a policy demands that emphasis and novelty be clearly indicated by authors and abstractors. Actually such failures are exceptional; chemists are usually astute enough t o know when they have discovered something new and they are understandably careful t o see that they receive proper recognition for their discoveries. Abstractors are more likely to be at fault. Chemical Abstracts now, with each sending of assignments, emphasizes the importance of making abstracts complete from the indexing viewpoint. The entries t h a t have gone into previous indexes also exert an influence on t,he selection of subjects and on the arrangement of the selected information t o fit in with the patt,ern of these indexes. There is a reluctance to start new headings unnecessarily. Old headings are made to do in some cases by wording the information in a slightly different manner. This is good indexing practice, for it prevents the starting of many headings which would complicate index searching more than they would help. This fitting of new information into t,he pattern of old-that is,
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the maintenance of a certain rigidity of structure-serves a very useful purpose in simplifying searches back through a series of indexes. This rigidity of index-heading structure must not be so great t h a t changes in the meaning of words or the introduction of new, useful words cannot be accommodated or assimilated. The question often confronts the indexer of deciding whether or not to index compounds which play a secondary role in a study: starting materials, intermediate products, solvents and other forms of reagents, by-products, and the like. Often these compounds should be indexed, but many times it would just clutter up a n index to enter them. The decision depends on the nature of the study. Whenever new information of any sort is provided, a compound should be entered, but an index would lose in value if it were filled with references to the mere mention of compounds in well known uses; the index user would lose time and be disappointed in being led t o such mention in abstracts. For example, it would be unwise t o make an entry for sand and lime every time glass manufacture was indexed and t o make entries for each reagent used in a n analytical procedure. However, if some starting material, the utilization of which is a problem, entered into the manufacturing process or some new and unusual reagents were used in an analytical procedure, there would be justification for index entries. Intermediates and useful by-products are often of interest. The building of good subject indexes is largely a matter of using-indexing help which is yell informed and of applying common sense. When the properties of compounds have been studied, including their effects, such as biological ones, entries are called for even though the results may be negative. Current interest in punched cards and their requirements has raised the question of the value of classification us. simple alphabetic arrangement in indexes as a means of locating information. An important factor is simplicity. Classification introduces complexities. A choice between these two forms of arrangement depends on the purpose and on the means a t hand,, The common alphabetic index is inexpensive and it serves most purposes best. It is the ideal method of pointing out individual items and small groups of information, and, used with ingenuity, will usually solve more general problems. For certain types of socalled generic searches, classification would be more effective, but an index or its mechanized equivalent would have to be built with that purpose in mind. One can get out of a n index or its equivalent only that which is put into it. There are many possible bases for classification in chemistry and no two individuals would classify in the-same way. An individual can classify information for his own purposes to be used by himself much more effectively than he can classify ’information for the various uses of many others. We maintain t h a t a n index pref pared for general use should use classification only in a limited manner and only in so far as it helps in the general purpose of a n index. Classification is a tool and not a n objective of the indexer. The classified index requires the user either t o learn the classification scheme or to consult it each time the index is used. This often puts an extra step into the path of those using the index. Whether the index builder is justified in making most of his customers take this extra step depends on the requirements of most of the customers. The main difficulties inherent in classified indexes lie far deeper than in just making the index user take a n extra step. Librarians are well aware of the difficulties in the various classification systems. The existence of many different systems for classifying knowledge is a sign t h a t no universal classification scheme is generally acceptable. It is easy for the library searcher to imagine all of the information he wants collected at one spot; he might devise a classification scheme t h a t would put i t in one spot; he might even go farther and prove unquestionably that his classification scheme would be inexpensive t o put into effect. What he may not understand is that, for the next
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problem t o which he is assigned, the index may prove of no value because he will then require a different classification. INDEXING THEORY AND THE INDEX USER
The views held by the indexer on the subject of building indexes will largely control the method of using the index. If the indexer selects only novel or emphasized information, the user willnot be able to locate trivial information. Should he be able to? By trivial information we have in mind the answer to questions like these: “In what papers published this year are 250-cc. beakers, or potassium permanganate, or oxidation reactions, or molecular distillation mentioned?” The searcher will be able to find only those papers in which these subjects were really studied with the provision of new information. Incidental mention, the words, will not be found indexed, If the indexer selects only titles, the user may miss information located in the bodies of the articles or abstracts. If the indexer selects only important words (word indexing), the user may miss subjects. The user, in short, is limited by the theories of the indexer. With an alphabetical index, the user in a sense constructs his own classification scheme by selecting a n array of headings under which he wants t o look. Thus, ’each index user can tailor-make his own classification scheme. This array of headings may consist of synonyms, more-general headings, more-specific headings, and otherwise related headings, such as those representing reciprocal topics.
For example: A chemist interested in something about hexoses would construct a n array concerning the “something” and concerning hexoses. For the second part of the array, he would probably find the most pertinent information at the heading Hexoses. If he desired t o extend his search, he would do well to include in his array of search places headings representing specific hexoses, as Glucose, Fructose, Galactose, Allose, etc. His array might profitably include more-general headings, as Sugars, Carbohydrates, Oses, Glucides, etc. He might gain useful information from related headings, as Pentoses, Glycosides, Arabinose, etc. The index user constructs his array with the help of dictionaries and other reference works; as he starts his search he is helped by cross references, whibh really constitute a rudimentary sort of array. Preformed arrays could be printed in a book which would resemble a thesaurus or put on punched cards. A preformed array might be compared t o a ready-made suit of clothes. It is possible t h a t the array suit could be made t o fit fairly well most of the problems a chemist meets. The chemist could then play tailor and alter the array exactly t o suit his needs more cheaply and more rapidly than by starting from scratch with yard goods-reference works. These arrays t h a t the user of a n alphabetical index may need t o construct are not, or should not be, static things. They should grow with the searches. It is difficult to conceive of how a novice could construct anything even faintly resembling a complete array. And everyone who starts into a new problem must be something of a novice. The growth of an array need not occur all at one sitting; as the laboratory research progresses, the array should expand. This is a n argument for making one’s own literature searches. The limit of usefulness of a n alphabetical index for a given problem is largely determined by the difficulty in forming a suitable array of search places. Difficulties connected with arrays are brought about by the size of the array, the searcher’s lack of knowledge and ingenuity, his lack of availability of suitable reference works, and the frequency of change of arrays. Thus, a n author writing a monograph on brominated hydrocarbons would find the ,Subject Indexes t o Chemical Abstracts not very useful because the array of search places would be so large. Putting it another way, the Subject Indexes to Chemical Abstracts were not designed for generic searches of this nature. This kind of search is regarded as too special to justify the expense of the
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much expanded indexes which would be required and, still more important, to justify the probable awkwxdness introduced into the index for the usual needs. SUGGESTIONS FOR INDEX USE
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Some suggestions may be helpful in effective use of the Subject Indexes to Chemical Abstracts. In index searching, there is a t least one field in which our knowledge is elementary: the psychology of the process. Research directors have reported difficulty in gett.ing their men to consult the literature. This difficulty may be caused by various factors. Index searching is a passive sort of thing compared to laboratory work; it is not so satisfying to the creative urge. Also, all of us feel a certain sense of bewilderment when we enter a library with a need to answer a specific question. Fortunately this feeling is usually short-lived and is often easily dispelled by start’ingto search almost anywhere, even in the less likely places. I t may be replaced by a feeling of delight in information and ideas discovered. As the search proceeds, there ,may develop a feeling of uncert’ainty as t,o its completeness. Information may never have been discovered, it may have been discovered but not published, or abstracted, or indexed, it may have been indexed in the wrong place,.or the searcher may be looking in the w o n g places. There is often uncertainty as t o how much effort one is justified in investing in a search. Furthermore, is it not true that research chemists sometimes search diligently in the literature for information that they hope they will not find? If they do find t’he information they seek, their research problem has evaporated. We can sympathize with those who feel baffled by indexes, for we often do ourselves. Let the baffled derive comfort in the knowledge that, if worse comes t o worst, t’hey can read every heading in the index and still be reading only 1’% of the words in the abstracts. The best place to look first in an index is the word coming first to mind. It is not wise to try to outwit the indexer, so t o speak. His first concern is putting the information where the user will look first. If the first word fails to disclose the information, then an array of search places can be made. The array is probably best started with synonyms-for example, vitamin BI, thiamin(e), aneurin(e), etc. When the index is searched for synonyms, “See” cross references may be found. These will lead to the headings of main interest. The remaining synonyms should be checked to eliminate the possibility of losses from scattering, especially “synonyms” which are trade names. After the main headings have been located, the array can be expanded to include more-general headings, more-specific headings, and otherwise related headings. Confidence in the completeness of the array can often be increased by noting the increasing frequency with which the same paper is picked up through different parts of the array. The array should expand with the literature search and also with the laboratory work. This index-searching process is a developing, unfolding sort of thing; it is really an educational processthe more one knows, the more varied is the information that becomes acceptable and useful. I t is highly improbable t’hat’ all the useful information will spring from the index a t the first. glance. Once a desired heading has been located, the best method of searching among the modifications becomes the next concern. Many times a glance will reveal the desired information or its absence. Under the larger headings, it will take something more than a glance. Since experience has shown it difficult to predict the word starting a modificat,ion, it may be necessary to read every modification. This is not such a loss of time as it might a t first seem, since it offers a good opportunity of discovery of substitute, related, and accidental information. The modifications can be arranged then into an order of probable importance to the index user, or a number of modifications can be se-
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lected and arranged, likewise. The list can be looked up, starting with the most important, and the process continued until too little relevant information is discovered to justify continuance. After the main ent’rieshave been looked up, read, and digested, it is sometimes well again t o read the modifications under the more important headings, since the increased background of lrnowledge on the subject will make more information understandable and a,cceptable t o the searcher. luow that a start into the literature has been made, the references found printed in most scientific papers will probably provide much further information. $uthor indexes are often of help, at this point, in locating more information, since authors tend to specialize in their research. I n some respects, searching the literature may resemble a. nuclear chain reaction; it may be difficult, to start, but once started, it’may be difficult t o control, since the reference multiplication factor is usually much greater than one. It is desirable to read the entries under a heading slowly because it takes time to add, from the imagination, the supplementary information that the indexer had to leave out of the index. One might think of an index user as a paleontologist. The entries he discovers are the bones of yesterday’s information. As he looks at these entry bones, he must judge, from their size, shape, quality, and location, to what kind of subject animal they belonged. The paleontologist reconstructs the whole animal from the fragment of bone he holds in his hand; the index user reconstructs the source information, with similar imagination, from the entry he holds in his mind. An index entry, “Phenanthrene, purification of,” suggests the possibility of finding the melting point of phenanthrene; it also implies a source of the compound and perhaps even a method of preparation. A melting-point apparatus is possibly described. The fact that an index entry seems, by its \%-ording,to indicate nothing new should not mislead t,he user, for it is frequently impossible to indicate the novelty in a modification of reasonable length. One should expect every index entry t o lead to novel or emphasized information. Some research chemists may feel that they do not have time to play index paleontologist; they have a research problem and must get on with its solution. To these impatient ones we say: Perhaps the index searching is not the main rate-determining factor in gaining information from chemical lit,erature in most cases. Perhaps reading and mentally digesting the information in the abstracts and original papers are the main factors. For those whose profession is index searching and compilation of bibliographies, this is not so. These chemists are most helped by improvements in indexes and searching methods. We have been building chemical indexes now for a good many years. We have long ago learned that indexing is a science and an art in itself. The chemical-literature worker misses an opportunity for experimental chemical work in the laboratory, but he can experiment’ with procedures in dealing with chemical literature and one of our most interesting opportunities for such investigation has been in connection with the indexing of Chemical Abstracts. This has involved much work with nomenclature, form, st,ructure, building procedures, safeguards for accuracy and adequacy, etc. We admit having pride in the indexes to Chemical Abstracts, but this does not mean that we do not expect t.hem always to be susceptible to improvement nor that our minds arc closed to thc possibilities of radical change in view of such developments as punched-card machines. At this point, however, it is bur conviction that the common alphabetic index is here to stay and that devices such as punched cards, which may or may not require a greater degree of classification of information, will be supplementary, though useful tools, particularly for special purposes, for which they must be built. RECEIVED August 28, 1947. Presented before the Division of Chemical Education, Symposium on Chemical Literature, a t the 111th Meeting of the AMKRICATC H E M I c a L SOCITTY, Atlantic City, N. J.
