NEW HORIZONS IN SCIENCE Introducing Dusts, Germs, Molecules, and Atoms WILLIAM J. WISWESSER Willson Products, Inc., Reading, Pennsylvania
THIS is a
of the = ~ ~ ~ to i tchemis. ~ t i Today ~ ~ there are 7,W0,000. I talked recently with a man who said that in his boyhood there wae not a single public high school try'' published in the June, 194%issue of THISJOURNAL in his state. 1892 there was just one high school on (page 271), which cautioned that the future of civiliza- the island of Manhattan. Even in 1910 not more than 10 per tion will be bleak or bright, depending upon how we cent of the young people of high school w e were in school; by think. how well we earnestlv trv to live toeethe-in the 1936the proportimn had risen to 36 Per cent. "
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neighborhood, in the nation, and in the world. Science, teaches us how to think straight, how to avoid deceit, and how to benefit mankind most by honoring the authority of Truth. The following views of new horizons present a novel and frankly untested approach t~ the brighter side of science, emphasizing old human interests and new human visions in structural chemistry. These views refleet the current consciousness of entering a new era in Power technology, in world politics, and in the educa tional aim to develop amore compatible blend of science DhilosoDhv, . " . economics, and ~eace-abidinereli&ns. he urgency of this general task was emphasized the numerous fearful predictions quoted in the preceding article. The ability of a nation to solve its comprehensive problems reduces to the ability of its individuals to grasp the menaces suddenly rising in nature's minute entities of radioactive dusts, epidemic gems, and 6ssionable atoms, T~ change these menaces to benefits, the average man must get a quick, yet lasting, visual appreciation of these minute entities, and this is the ~ ~ - toh immediate goal for the ~ ' ~ introductionn chemistry given below. The importance of strengthening and expanding our mental horizons was evident in the recent meeting of the Society for Promotion of Engineering Education, now named The American Society of Engineering Education (1). President Harry S. Rogers recognized "the growing conviction that engineers should have a better understanding of human relations and the impact of technology on society." Educators must help "by associating themselves with historians, economists, and philosophers. . . ." Critics of the unconventional approaches given below must recognize that education itself is an experimental art or science which is entering a new era. Its inconspicuous expansion since the turn of the century recently was emphasized by James Creese, President of Drexel Institute (8).
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In this connection, it is helpful to recall that one of OF CHEMICAL EnUCAthe declared aims of the JOURNAL TION "is to make the theoretical and practical progress of chemistry intelligible to those of limited training and experience" (3). Finally, the new task for every ~ ~ can chemist was suggested by E. B. Wilson.. Jr.., in reYiewing "One ~ o r l d o N r ~ (4). ~ ~ '
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Because chemists had s. major share in bringing the bomb into chemists have a special rresponsibility for using their influence and their understanding of the problem to educate the public and especially our politicians and statesmen of the neoee sity for intelligent action before it is too late.
chemists musthelp convince the world that ~ but L ~ hope,,, isnot utomorrow~stargetx
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OLD HUMAN INTERESTS In the small world around us there have been a thousand things to stir our curiosity since our earliest childhood days. While the questioning spirit of those days may have been dxndoned long ago, i t was not because satisfying were found. From the nursery up, ~ ~ answers ~ such questions as:these are still profound: Why is salt so sdty? m y is sugar sweet? Why are some things poison? Others good to eat? does ice keep Why is fire Why is oil so oily, when other things are not? mat makes glue so sticky? Why does jelly What makes leather tough, and rubber stretch so well? Why are leaves all green? Why is snow pure white? Why does perfume smell? What is dynamite?
Why.. . ? After a moment's consideration, it must be confessed that the sophisticated answers hardly begin to explain. The bud cells do not explain taste; chlorophyll does not explain plant greenness; oxidation does not explain fire. almost every walk of life, as the followingquotations will show, such simple queries can be found. pioneers of science made much of them, approaching the curiosities and mysteries much like little children, with wide open eyes, unprejudiced minds, At the time of the Philadelph~acentennial there were not and feelingunsatisfied with halfway explanations. The modern inquiring mind, as descriped by Profesmore than 70,000 students m all the high schools of the country. 21
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JOURNAL OF CHEMICAL EDUCATION
sor C. C. Furnas in his "Next Hundred Years" (5), sued indigo, madder, and Tyrian purple? How do they wonders: become fixed to cloth? Food is still a major interest throughout life-an urWhat sends sap to the top of the tree? gent interest throughout the world. What guides the What causes cancer, or the common cold? important magic from planted seed to harvested plant? What is a satisfactory anesthetic for childbirth? What are the fundamentals in the simple muscular eontraction How can soil fertilitv be sustained. or crou vield and in walking around? quality improved? " What cause; growit? What .. . Almost every scrap of scienoe is vitally involved in human stimulates, suppresses, or eventually limits it, in any ezistmee, and fortunately, the more intelligent American is living thing? How do the hardy plant seeds and miinterested in these things. croscopic spores survive long periods of suspended aniThis same inquiring spirit in chemical education re- mation? cently was emulated in a poetic editorial by Professor Life itself, that hardy yet delicate, tremendously N. W. Rakestraw, concluding with this inspiration complex balance of chemical changes, is a continual (which is fully appreciated only by reading the entire source of very human interest from the moment a threeeditorial) (6) : year-old realizes that babies must come from someAnd on and an, no stop in such a quest; the far horizon still where. Need i t be mentioned that man cannot yet eludes us-always will. control sex determination, much less sex itself? Every But the wider and the longer is the path we tread down in the person living today is descended from an unbroken search, the richer all our life becomes. million-year-old line of ancestors who had mated a t And still we are content to reach no final end. least once in their life. It is fairly certain that most of Something deep within us drives us on. Man would be less than man without it. these ancients hardly knew why they mated, nor sensed In that same issue (7) a radio talk by John Kirkwood the consequences. They were simply obeying a bewas reprinted, giving a wondering "View of the Molecu- havior pattern (like mother love) dictated by certain lar World." He recalled such everyday questions as: amazing chemicals in the blood stream. These biochemical complexities evolved from processes that Why is an alloy steel strong? took millions of years to perfect-is it any wonder that Why is glass brittle? we are just beginning to untangle the simplest of these Why can rubber be bent and stretched? Finally, how are the properties of the resulting substances related "nursery" questions! What are these powerful hormone chemicals, and to the architecture of the molecules? how do they work? How do such "mere chemicals" The electron microscope, now reaching to 200,000 mag- determine whether an almightly human be clever or nifications, has helped tremendously in bridging the gap feeble, strong or weak, great or small, agreeable or disbetween microscopic (X 1000) andmolecular (X 1,000,- agreeable, domineering or condescending, masculine or 000) vision; and the builders of America's first mag- feminine? Human behavior, judging by the hormone netic focusing electron microscope-Professors Burton discoveries of the past few decades, is predominantly and Kohl-raised similar questions in their story of guided and controlled and balanced by these daily thismarvellous new instrument (8): traces that pour into the blood stream from the ductWe have many natural phenomena to theorize about. less or internally secreting glands. What is heat? What is sound? What is light? What is graviHow do narcotic drugs, those extremely potent plant tation? products, produce such highly specific and mentally Does a person ever tire of the fascination of a fire? A irresistible actions on the human body? Why does an log-pile of burning wood stimulates almost all of the excess of alcohol bring on a reeling drunkenness that senses, and the curiosity: What causes the smoke? makesman worse than beast in hismanners? Why must we eat in order to live? Why do we need the flickering flames? the soothing "throw" of ember heat? the appetizing odors? the crackling noises? a particular balance of fats and starches, a minimum reor the charring and disappearance of the original bulk? quirement of proteins, and scarcely detectable traces In the garden the most casual observer is caught by of minerals and vitamins? How do vitamins work? the wonder of color. What is it, fundamentally? Do How do enzymes digest and liquefy coarse lumps of other animals see it as we do? How are colors made food? Why is there an almost universal appeal in in the flower? Why are there no blue roses? Why do subtle blends of flavors, spices, sweets, and hitters? the blues fade so fast? Why are blue, pink, and violet Why do tastes differ a t all? How are odors detected usually associated separately from the red, orange, and by nerves? Atomic energy, that confusing and misleading catchyellows? In the fall the green leaves turn yellow, orange, red, then brown. So commonplace, it hardly word loosely referring to the large scale transformation of matter into energy, brought a burst of new questions: causes prosaic comment. But what goes on? Coloring materials are of tremendous interest because What are atoms? How small are they? How indemodern society needs dyes for the textiles, pigments for structible? What do they look like? (Surely not those dynamically asinine ellipses?!) What is this heat protective paints, and inks for writing and printingnot to mention cosmetics for enhancing the romancing. flash? Radiant energy? Radar? How can particles What makes a good dyestuff-like the anciently pur- of matter--at rest and occupying space--in any way
JANUARY, 1941
change to waves of energy that do not occupy space and race away at a thousand-million feet per second? What are giant molecules, virus bodies, bacteriophages, or hereditary genes? What do all these things look like? Do we know for sure, or are we dreaming it up for the Sunday papers? In the universe around us exist certain real e n t i t i e e particularly matter, energy, and their intermingling action. These entities have always existed, and would continue to exist, whether we knew of them or not. It is the task of basic science to learn all that it is possible to learn about these realitiesnot merely for idle entertainment or for curiosity, but because as Roger Bacon predicted in the 13th century, knowledge i s power!' Our lives and welfare are vastly improved by our proper, honest understanding of these realities. Just beyond understanding, we can begin to harness these great actions and reduce our living labors; we can protect our societies from the catastrophies of flood, famine, pestilence, or political disease which would furiously and mercilessly destroy us, one and all. When the science trail begins to turn from the mild descriptions to more potent tables, graphs, and formulas, many faint hearts fall out. Most people need a special invitation to the terse literature of science, for they doubt whether the written page is sufficiently versatile to be very inviting in its treatment of these interests. It all depends upon the point of view: The little written word, man's marvelous invention for communicating his ideas, might he regarded as a shy old friend-in fact, one of the oldest friends of mankind. He exists mainly to please you, to help you grow in mental stature, knowledge, and power. He will guide, but not push you; should you tire of some details, he will not be offended if you skip and hurry on. If some difficulty halts you, he never hesitates to explain over and over until you are satisfied. And while he surely is unable to answer all your questions, he never shouts at you in a loud and impressive manner to conceal thereby his ignorance. He will not laugh a t yours. He asks for no fees, not even your undivided attention. He knows his place, and if you tire of him and cast him aside, he stays aside with infinite patience until you want to see him again. This is not a new point of view about the written word. It is a 14th century inspiration, a devotional tribute to books, very appropriately selected by B. A. Soule in his "Library Guide for the Chemist" (9):
Whosoever, therefore, aoknowledges himself to be a ze~lous follower of truth, of happiness, of wisdom, of science, or even of faith, must of necessity make himself a lover of hooks. -Richard de B w y , 1344 (published 1474)
Introduced in this way, chemistry easily becomes as human as history-and far more personal. NEW HUMAN VISIONS
Vision implies higher or deeper understanding. Its relation to seeing is obvious because about 90 per cent of the impressions that stimulate the brain are received through the eye nerves. The vertebrate eye, in both range and sensitivity, still greatly exceeds any manmade instmment. Its compactness, hardiness, and usefulness are truly remarkable. Consider, for example the winged eagle's ability to recognize small prey from a distance of a mile or more. Burton and Kohl began their informative story of the electron microscope with a chapter on vision and this immediate tribute (10): The human eye is a, wonderful optical instrument, more wonderful than any that man has ever devised. It unfolds to our mind the world that surrounds us and is the link which enables us to take s conscious part in it.
Man is descended from a line of animals which had developed special sense organs of sight a t least 400 million years ago (e. g., the compound eyes of the Cambrian Trilobita). Yet for more than 1000 years learned men believed that the mechanism of seeing involved al%hrowing-out" of filament receptors by the eye onto the objects which it perceived. A similar naive view that a filamentary "beam" connects light source and receiver persists to this day. Such views had to he questioned 300 years ltgo when Leeuwenhoek and Galileo invented two new instruments which extended man's vision to the microscopic and astronomic worlds. These inventions so greatly intensified the powers of human vision that they founded new fields of science; hut still the fallible, questionable human eye was the ultimate receiver. More than 100 years ago skeptical men had no way of truly knowing whether any two people saw exactly the same things. Frequent disturbances, such as dreams, visions in disease, hallucinations, and color-blindness, collectively tended to obscure any certainties of ohservations. Then in 1839 Daguerre and Nience perfected silver-plate phot~graphy.~ The discovery of photography was a profound step in man's learning. It led to further inquiries and important discoveries on the nature of light, visible and These are the masters who instmct us, without rods and ferrules, invisible, and eventually served to consolidate man's without hard work and anger, without clothes or money. knowledge of the universe-not only beyond the clouds, If you approach them they are not asleep; but within the molecules. The photographic method If investigating you interrogate them, they conceal nothing; If you mistake them, they never grumble; gave an absolute graphing of light, a permanant recordIf you are ignorant, they cannot laugh at you. ing of many v i s i o n s i n ultraviolet, X-ray, and radioThe library of wisdom, therefore, is more precious than all riches, and nothing that can he wished for is vorthy to be compared active rays. With its modern extensions into color, television, and electron microscopy, this new tool of with it. science has revolutionized methods in astronomy, spec-
' The year 1945 brought a correction to this old paragraph, in the subtly introduced banner phrase of thcA.C.S. publications, "Science Is Power."
' For a fuller appreciation of photography, see W. C. Oelke's article in THISJOURNAL, 23, 593 (1946).
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JOURNAL OF CHEMICAL EDUCATION
troscowv, .- . and militarv science, and incidentallv has given the average man a precious new amusement. The pho+~Xraphicmethod first aided atomic structure studies by recording the thousands of radiation frequencies rnitted by activated atoms and molecules, ~~~i~ it aided in recording the kinds of scattering patterns produced when X-rays pass through solids. B~ analvzinp these watterus, i t was oossible to deter" mine with great certainty the actual space arrangements of atoms in many crystals. A similar structure analysis of gaseous or volatile substances was made possible by their diffraction of an electron beam, and again the photographic method served for convenient recording. These are just three examples of many methods of inquiry into the nature of thingsmethods that were completely free from the psychological uncertainities of ordinary human vision. [Only quite recently have any capable scientific thinkers re-examined the question of how the sense of human vision may reach out beyond the physical to nonphysical or extra-physical worlds. One of the world's outstanding astronomers, Gustaf Stromberg, popularly summarized an impressive treatment of this question in his "Soul of the Universe" (11). The profound unifications that were developed in this book and in the more recent "Autonomous Field Theory" (id) are bound to stir new views and broaden man's psychophysical horizons.] The convergent results of all the recent physicochemical structure inquiries are summarized by Professor Linus Pauling in his Willard Gihbs Medal acceptance address (15):
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even the shapes of such important molecules as serum proteins, enzymes, genes, the substances which make up protoplasm. . . . I believe that the next 20 years will be as great years for biology ,d medicine as the past20 haye heen for physios and chemistry.
HOWCan these old human interests and new human visions be utilized in an introduction to chemistry? Urnally when a man takes a new task or study, or joins a new institution, or enters a new field or strange land, he is given a brief orientation of some kind-an outline, an "introduction" tour, a sightseeing review, a chart or map-in order to grasp an appreciation of the horizons before submerging into his immediate details. In the same spirit it might seem profitable to introduce chemical science with a quick literal sightseeing tour from intimately familiar visible things down a dimensional ladder to pictures of interesting intermediate particles, thence to molecules and atoms.
SEEING MOLECULES
The extraordinary minuteness of molecules cannot be described by a shower of verbal superlatives, such as "exceedingly tiny, infinitesimal, indescribable, inconceivable and unbelievable!" The great Lord Kelvin, famous English scientist, often cautioned his listeners with this reminder: "When you can measure what you are speaking about, and express it in numbers, you know something ahout it." New and difficult concepts usually are learned in a stepwise manner, seeing new things in terms of those already understood. It seems most logical, then, to approach a visualization of molecules through a stepwise approach of size reduction^,^ beginning with Only a quarter of a century ago, there was not known the familiar and symbolic unit-entities, such as common distance between the stoms in the molecules of any gaseous garden seeds, garden-variety microbes, and submicrobes. substance, nor, indeed, of any orgsnio substance whatever.. . Seeds in particular are importantmany will reIt was not until 1929, when the technique of electron diffraction member how preciously the food seeds were regarded by gas molecules was developed by Mark and Wierl, that it became possible t o determine the interatomic distances in a that were sent to G. I. outposts far from home. To an ever-hungry world, the introductory remark by H. large number of organic molecules. Chambers in the Encyclopaedia Britannica (15) is a Today's commonplace descriptions of the distances, sober reminder: angles, and even vibration modes between the atoms See& are the keystone to the agricultural and horticultural in molecules cannot be appreciated without recognizing the vast range of the dimensional "forest" now open for industry, an industry which is vital to the life and prosperity of exploration. Pauling emphasized this "size apprecia- every country. tion" very effectively in his Westinghouse Forum adDusts have gained a new prominence since the lethal effects of radioactive dust from nuclear fission have dress (14) : Forty years ago the dark forest of the dimensional unknown been emphasized, but dusts always have been important stretched from this (1 micron) limit of the visible microscope in industry because of their contaminating, explosive, back indefinitely into the region of smaller dimensions. In or health hazards. It is almost certain that the average recent years the region from lo-' down to 10-1%cm., containing person has a very inadequate appreciation of the atoms and simple molecules, has been thoroughly explored by minuteness of biologically effective dust (or mist) an expedition outfitted with X-rays and similar tools, and the physicists are strongly pushing back into the region of the struc- particles, and this particle size exhibit will do much to clarify old notions.. t u x of atomic nuclei, below lo-" cm. Widespread DDT spraying also draws attention to Another detailed exploration is being carried out with the electron microscope. This has pusbed the nearer boundary of the importance of fine particle size for effective dispersal. the unknown back from to 10-6 cm. . . . For examnle. a new Public Health Renort on "Ablane The answers to many of the basic problems of biology . . are ~nwlication bf DDT Aerosols" (16) gves the following hiding in the remaining unknown region of the dimensional forest, mostly in the strip between 10 and 100 A.U., 10-7 and magazine used this method in a widely popularized
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10-Qcm.; and it is only by penetrating into this region that we We do not know, except very roughly, can track them down.
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article on science (frontispiece illustrations in Reference 8, but the geometric s t e p were not evenly spaced.
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I. T HI E "SEED=RANGE (a5 s e e n
1500
II.THE'GPnlN RAN6E
111. THE "GERM RANGE
- ~L I M I T O F- "SHOPPING" - VISION m n or
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I
x 20
MASNlFlCATlON
L I M I T O F OPTICAL MICROSCOPE
X ZOO0
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. , I = O . O I H M = lo fA
X 200,000
1 . . , , ,
,
150m i r m s away)
N.THE "GIANT-MOLECULE S E P ~I 5 n l i r o n s
-
100 MM
- L I M I T OF SIMPLE
see" 0.15m m or
(&
5 ft away)
or
RANGE-LIMIT OF ELECTRON MICROSCOPE i i O O O Angsfrmi
, i=o.lp=
away)
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V. THE XTOMIC" RANGE L I M I T OF CERTAINTY ( x w e n 150 &lgstroms away)
Ths "Vie.ainv dilltancad' ara relative to a normal reading dirtance of 30 cm. or 1 foot. on the moon (254 million tim-s fsrther .ray).
1000 8,
X 20.000,OOO
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,
,
.
,
8
I ,I M p 1 0A
Thus atoms S ft. away are about u easy t o .w up.-
JOURNAL OF CHEMICAL EDUCATION
data on "the approximate number of droplets formed fromO.l lb. of RDT per acre as a 20per cent solution in Velsicol NR-70." PARTICLE DIAMETER
(MICRONS)
NO. OF PARTICLES FORMED PER SQ. m.
These figures emphasize the mathematically obvious conclusion that a tenfold size decrease could cause a thousandfold increase in the effective dispersal of the "ray. Germs always have been important-yet difficult to appreciate because of their minutenessand the choice selections recently described (17) for bacterial and virus warfare are bound to command interest. In the interests of security alone, the widespread publication of microscopic pictures of the great epidemic menaces would seem to be justified. Molecules can be visualized through this "sizeladder" medium, in an entertaining and impressing manner, with the ridiculously simple "apparatus" of a 6" X 8" X 8" box of 24 medicine bottles, supplemented by half a dozen poster charts or slides. The 3-ounce bottles are partly filled with various familiar things, such as seeds, pollen, starches, imitation red blood cells and germs, suspensions of lacquer pigment, India ink, gelatin, mucilage, and water-all selected to make a uniform geometric progression in size, and filled to contain a calculated fixed number. The bottles are numbered from 1to 24, and the listeners are permitted a bit of wild "bean-jar" guessing before
being.told that this number reveals the number of zeros in the figure enumerating the contents. Table 1 gives the pertinent data on 24 random items suggested for their probable interest and convenience. If more careful thought is given to the substances (e. g., seeds selected for their suggestion of the molecular notion of a functionally ultimate unit), an enthusiastic group can develop a series of size-fixing objects they will never forget-much less doubt the seed-like realism of molecules. The supplementing diagrams obviously serve to give uniformly gaged magnifications of the bottled samples and auxiliary objects of guaranteed human interest, but particularly to give realistic pictures of molecules and atoms. The power of the illustrated magnifications can be appreciated more fully by paralleling with corresponding reductions of large scale objects. For example, a 20-fold reduction would shrink human stature to a 3inch doll size. A 2000-fold reduction would bring the Empire State Building down to a 7-inch model. The 200,000-fold magnifications would he inversely comparable with a rocket-nose view of the earth from its 40-mile level (taking one foot distance for close vision). Such a 200,000:l scale reduction would make the entire metropolitan New York area fit in one square foot, from the lower tip of Staten Island northeast to the Connecticut state line. Sizes would appear exactly as shown on the "Esso" road maps of this area (3 miles per inch), with 42nd Street only inches long, shore to shore.
TABLE 1 A Particle Size Perspective Scale Pmtiel
Bottk No. (0)
Biological Ezampks
Other Ezamoles
Eggs, walnuts Braeil nuts, acorns Corn, beans Wheat, lentils Rape, flaxseed White clover Red top, portulaca Lobelia Large diatoms Potato starch grains Average pollen grains Cornstaroh, amoeba Red blood cells Bacilli Chromosomes Micrococci Cowpox (vaccinia) Mosaic virus Bacteriophages, genes Antibodies, enzymes Starch molecules Gelatin molecules Mucilage molecules Glucose molecules Water molecules Hydrogen molecules
Golf balls Coins (nickel) HAIL Fine gravel RAIN Coarse sand DRIZZLE Average sand MI~T Fine sand HEAVYFOR Road dust LIGHTFOG Silt Harmful dust Clay Metal fumes Paint pigments Blue smoke India ink hlack Collodion Egg albumen Tannins Kerosene Ammonia Helium
Pa~lick Sire "Stations" 2 em. 1 cm. 0 . 5 cm. 0 . 2 cm. 0 . 1 om. 450 microns 210 microns 100 microns 45 microns 21 microns 10 microns 5 microns 2 microns 1 microns 0 . 5 microns 0 . 2 microns 0 . 1 miorons 450 Angstroms 210 Angstroms 100 Angstroms 45 Angstroms 21 Angstroms 10 Angstroms 4 Angstroms 2 Angstroms
n grams t8 2 1 0 -1 -2 - 3 - 4 -5 -6 -7 - 8 - 9 -10 -11 - 12 - 13 - 14 - 15 -16 -17 -18 - 19 -20 -21 -22 -23
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Wumber in Medicine Bottle
JANUARY, 1947
The 20,000,000-fold magnification, which a t last brings distinct atoms into view, compares inversely with a surface seen 4000 miles away. From this nearvanishing point, the body of the moon, for example, would look as large as a 200-foot perisphere viewed from across the extremes of a football field (i. e., 145 yards). It would have an angular diameter of about 15 degrees, and since this viewing distance is ahout 50 times closer than the earth, a 50-power telescope would he required to produce this view from the earth. Summarizing these comprehensive size ranges, one might remember that i t is about as easy to see bacteria, vimses, and atoms on the surface of a howling hall as it is to see-from near the moon-destroyers, men, and marbles on this earth. For an emphatic conclusion, quantitative comparisons may be added, proving for example that there are (1) as many atoms in a red blood cell as blood cells in the human body (loL3), (2) more molecules in a quart of water (loz5) than there are quarts in all the oceans (loz2), (3) far more molecules of air in an empty milk bottle (lo2=)than stars in the Milky Way (101°), (4) more gas molecules hitting each mm. square of graph paper than there are mrn. squares in a flagpole stick of tissue-thin regular size graph sheets, (5) 30 million molecules per cc. in the best possible laboratory vacuum, atm., even after the traces are chased by the chemical "getter." Interstellar space is estimated to be a million times rarer, or 1mol./cc., atm. (the molecule is most likely hydrogen, fuel for the stellar furnaces), and (6) more air molecules in a single cubic millimeter of air than can be represented by mm. squares in a stack of graph paper reaching halfway around the world: 2.7 X 1016mols. (1 atm., O°C.), 2.0 X 1016mm.squares (10' per running mm.). ~ h e s sugges$ons e of particle size pictures and samples
help convey an instantly effective introductory appreciation of atoms and molecules. As long as "seeing is believing," visual aids such as these help most in fixing a reasonably convincing awareness of these basic entities which are the exclusive concern of chemistry. If the new student or troubled layman is visually convinced that atoms and molecules are not the fairyland concepts of Boltzmann and Mach's generation, and if he is given a fairly good picture of these ultimates as we now know them, he will be far less "baffled to inaction" by the fearful or wonderful potentialities of synthetic chemistry and nuclear physics. ACKNOWLEDGMENTS
The assistance of Shaeffer's Seed House in collecting the seed samples, and of Mr. John Beck in making the seed prints, is gratefully acknowledged. LITERATURE CITED (1) ST& REPORT, Chem. Eng. News, 24, 2036 (1946). J.. J . FranklinInst.. 242. 15 (1046). (2) CREESE. RAKESPRATV, N. w., A.C.S. h. i , p 29 (1946). WILSON, E. B., JR., Chem. Eng. News, 24, 2112 (1946).
NO.
FUENAS,C. C., "The Next Hundred Years," Reynal & Hitchcock, New York, 1936. F~AKESTUW, N. W., J. CHEM.EDUC.,22, 417 (1945). KIRKWOOD, JOHN,ibid., 22, 462 (1945). BURTON, E. F., AND W. H. KOHL,"The Electron Microscone." 2nd Ed.. Reinhold Publishine Cornoration. New
Reference No. 8, p. 13. STROMBERG, G., "The Soul of the Universe," David McKay Company, Philadelphia, 1940. STROMBERG, G., J . Franklin Inst., 239,27 (1945). PAULING. L.. Chem. E m . News. 24. 1788 (1946). . . PAULING; L.; ibid., 24, i375 (1946)'. CHAMBERS, H., "Encyclopedia Britsnnica," 20,277 (1930). Knum, C. W., AND R. L. METCALP, Public Health Repfs., m. iixn i i o--,. m .., ---(17) SHALLET,S., Reader's Digest, 49, 29 (1946). \."
