AA SplashSplash fromfrom thethe PastPast !! ChemSurf SomeMatters

A Different Approach

Fizzies—A Splash from the Past n this issue—the first in our 16th year—we unveil new departments for q Fizzies ChemMatters. One of our goals for www.fizzies.com I The official home page for Fizzies has more from Premiere Innovations. ChemMatters is to keep up-to-date, and so q The American Dietetic Association we are striving for the look and feel of the www.eatright.org/asweeteners.html current trends in magazine publishing. This page records the position of the ADA on the use of nutritive and nonnutritive sweeteners. This new look includes the ChemSurf department we introduced in the last issue Lindow Man—Murders in a and another department called SomeMat- q The Bog Page ters devoted to editorial notes, including www.jamesmdeem.com/bogpage.htm these comments. This department will also This Web site by James Deem, Bodies from the Bog, catalogs and discusses bog bodies. q Science at Work include your letters and comments, special www.campus.bt.com/CampusWorld/pub/ScienceNet/slup/Interviews/vincentd.html announcements, and updated information This site includes a discussion of the preservation techniques used for on articles from previous issues. Lindow Man. You will still see the familiar four “fea- Color in a Capsule ture” articles. From past evaluations, we

q Silly Putty on the Web have noted that most of you enjoy reading www.vern.com/sillyputty about mysteries and consumer products. This page lists some interesting trivia, uses, and history of Silly Putty. In response, we are making a commitment q The Art and Science of Microencapsulation to present articles of these types in each www.swri.org/3pubs/ttoday/summer/microeng.htm This article from Technology Today is a nice summary issue. In this and future issues, two of the of the microencapsulation industry. articles are presented as departments— Ozone Out of Bounds MysteryMatters and ChemSumer. In these two departments, you will q Ozone Transport Assessment Group see the use of symbols from the Periodic www.epa.gov/oar/otag/otag.html This Web site addresses OTAG and its Table of the Elements. We think it is appro- concerns for ground-level ozone. priate to connect ChemMatters articles q Georgia Tech Atmospheric Sciences with something familiar to all of us—the www-wlc.eas.gatech.edu/wlc.html This Web page by William Chameides, elements—and how they relate to the arti- Regent’s Professor, goes into more detail on cles. Look for links between the article and research of ground-level ozone. the element. Other Fun and Interesting Sites A fifth and final department—still in the planning stage—will seek more q MAD Scientist Network madsci.wustl.edu involvement from you. We want to print Some 500 scientists are working in this network to answer about 250 questions from stu- questions from you on a chemical topic dents a week in 26 areas of science. You can ask a question by completing the form you have always wondered about. If your under Ask A Question. However, check the archived questions or answered questions first to see if your question has already been answered. Just click on Recently Answered question is selected, it will be answered in Questions or The MadSci Archives to check. If you are interested, you can browse the a future issue. answered questions in a given area and check the ones that look interesting to you. This Your comments and suggestions are is not a site to ask homework questions. valuable. We like to hear from you, and we welcome your questions as well. Send your Correction: An error occurred in the illustration of cellulose appearing in the article, questions or comments to me with your “Counterfeit Detecting Pens” (October 1997, p. 14). The hydroxymethyl group appears on the wrong side of the molecule in every other molecule. A corrected version of the name and school affiliation to e-mail: polymer appears below. [email protected]; or write: ChemMatters, American Chemical Society, O O O O O 1155 16th St., NW, Washington, DC 20036-4892. O O O O

Cellulose Michael Shea

2 ChemMatters, FEBRUARY 1998 February 1998

DEPARTMENTS 2 ChemSurf

SomeMatters 2 A Different Approach ChemSumer 4 Fizzies—A Splash from the Past What sets Fizzies apart from other powdered drinks? The chemistry of the fizz in Fizzies is explored. MysteryMatters 7 Lindow Man—Murders in a Bog A well-preserved body is extracted from the Lindow Moss bog, but whose body is it? The quest for an answer has led to exciting insights into the life of ancient Britains. The Puzzle Page 16 Elemental Punishment Some of the clues of this crossword puzzle contain clever elemental puns. FEATURES 10 Color in a Capsule Silly Putty is but one example of how microencapsulation technology is used to create products that change to a different color and then change back again. Ozone Out of Bounds 13 We frequently hear about our need to protect the ozone layer, but ozone can be bad if it accumulates at ground level. ChemSumer

Fizzies— A Splash from the Past

By Brian Rohrig the distinctive “plop, plop, fizz, fizz” In search of a hey’re baaack . . . a splash sound for which they have become sweetener from the past! Fizzies instant famous. These scientists thought it T sparkling drink tablets, popular would be great if they could duplicate In 1968, Fizzies were removed in the 1950s and 1960s, are now back this effervescence and create a tablet from the market in the United States on the market. What sets them apart that would make instant soda pop because they contained cyclamates, an from other powdered drinks is that when dropped into water. Thus, Fizzies artificial sweetener. Cyclamates were they bubble and fizz when placed in sparkling drink tablets were born. They banned because of a study that found a water, forming an instant carbonated first appeared on the market in 1957 possible link between this substance beverage. Simply place a tablet in a and became wildly popular, sweeping and cancer in laboratory rats. However, glass of water and watch it fizz for a U.S. and international markets. according to the U.S. Food and Drug minute or so. After the tablet has Administration (FDA), 75 subsequent completely dissolved, drink up! studies have failed to demonstrate that Fizzies were formulated by cyclamates are carcinogenic. Because scientists at the of the initial study, however, all prod- Emerson Drug ucts containing cyclamates Company in the had already been removed 1950s. The from the market. Cyclamates researchers had been are currently under review by working with sub- the FDA, which is considering stances similar to their possible reintroduction today’s Alka-Seltzer, a into the U.S. market. They are popular antacid. Alka- already in use on a limited basis Seltzer tablets, when in other countries such as Canada dropped in water, produce and Australia.

4 ChemMatters, FEBRUARY 1998 Relative Sweetness of Several years after Fizzies were banned, Sugars and Sugar At higher temperatures, less gas is able the formula was purchased by Premier Inno- Substitutes to dissolve in a liquid. If Fizzies are made with

vations, Inc. The company immediately warmer water, less CO2 remains in solution, began searching for a suitable substitute for and the drink tastes “flat.” If you don’t drink

cyclamates. An artificial sweetener was up right away, much of the dissolved CO2 gas essential, because such sweeteners are much will diffuse into the air, leaving behind a fizz- sweeter than ordinary sugar (sucrose) and less sweet liquid.

only very small amounts are needed. Cycla- The Fizzies label does not list CO2 as an mates are almost 45 times sweeter than ingredient because the CO2 is formed in the sugar. drink as a result of a chemical reaction Today’s Fizzies are made with aspar- between the first two ingredients listed: citric tame, often marketed as NutraSweet, which acid and sodium bicarbonate. As soon as a is about 200 times sweeter than sucrose. If tablet hits the water, a gas is released, indi- sugar were used in Fizzies, each tablet would cating that a chemical reaction has occurred Cyclamate Aspartame Glucose Frucose Saccharin be the size of a hockey puck, making it diffi- Sucose (see Reaction 2). cult to fit into a glass! After many years of The other ingredients in Fizzies, such as research, the newly reformulated Fizzies were artificial flavors, aspartame, and ascorbic put back on the market in 1995 and have hese values are averages; relative acid, combine with the products of this reac- steadily gained in popularity. Tsweetness depends on temperature, pH, tion, to give Fizzies their unique taste. The fizz in Fizzies and other substances in sweetened food. Neutralizing Fizzies For example, aspartame and saccharin The fizz in Fizzies is caused by bubbles decompose at high temperatures; conse- A bubbling glass of Fizzies drink is a of carbon dioxide (CO2) gas that are released quently, they cannot be used for cooking. good example of a neutralization reaction. An when the tablet is dropped into water. Careful Cyclamates, however, can withstand the acid and a base combine to form three prod- observation reveals that these bubbles high temperatures of cooking. ucts—sodium citrate (a salt), water, and CO2. always rise to the surface because CO2 gas is However, because some of the CO2 combines much less dense than water. However, not all with water to form carbonic acid, the final of the CO2 gas rises to the surface; some of it product registers an acidic pH. The tablets dissolves in the water. The dissolved CO2 can are enriched with vitamin C (ascorbic acid), react with water to form carbonic acid, H2CO3 which also helps to lower the pH. (see Reaction 1). For the reaction between citric acid and ↔ sodium bicarbonate to take place at an appro- H2O(l) + CO2(aq) H2CO3(aq) priate rate, large numbers of citric acid mole- Reaction 1. The fizz in solution cules and bicarbonate ions must be able to One of the ingredients on any soft drink label collide with each other. In the solid powdered The pH of the Fizzies drink registers is carbonated water, which is another name state, the reactants lack mobility, so fewer between 5 and 6, showing that the resulting for carbonic acid. However, in the production effective collisions occur and the reaction is

solution is clearly acidic. Carbonic acid is of soft drinks, the CO2 is pumped into the slow. After dissolving in water, each molecule found in other carbonated beverages as well. solution under high pressure at the bottling and ion is freed and can move about indepen- plant. dently in the solution. This allows a much The directions for Fizzies state to add greater number of tiny, highly mobile mole- the tablet to cold water. Milk can also be cules and ions to collide.

H3C6H5O7(aq) + 3NaHCO3(aq) → Na3C6H5O7(aq) + 3H2O(l) + 3CO2(g) citric acid sodium bicarbonate sodium citrate water carbon dioxide

Reaction 2. The reacting ingredients in Fizzies

used, producing something like an instant The term aqueous solution (aq), used in root beer float! Although Fizzies sparkling Reactions 1 and 2, is another way of saying drinks taste better cold, what happens when that a substance is dissolved in water; thus, it you drop a tablet in warm water illustrates exists either in the form of molecules or ions. PHOTO COURTESY OF PREMIERE INNOVATIONS, INC. some interesting chemistry. Fizzies are stored in sealed pouches with a

ChemMatters, FEBRUARY 1998 5 Mini-Fizzies Activities

You can do some activities to learn more about how Mini-Fizzies behave. • Which dissolves faster, whole Mini-Fizzies or tablets crushed into many pieces? • Does temperature play a role? Try Mini-Fizzies in different temperature water. • Does concentration matter? Try dissolving Mini- Fizzies in an already acidic drink like coffee or orange juice. • Why does the candy always rise to the surface before it finishes dissolving?

foil lining to keep the tablets dry and it immediately reacts with saliva and begins and prevent a premature reaction to fizz, for a very interesting tingling sensation. with water from the air. A chemical reaction in your mouth—the water in the saliva causes the citric acid and sodium

Fizzies bicarbonate to react—produces CO2. versus Pop So what’s the difference between Mini- Fizzies and Pop Rocks? Pop Rocks do funny Rocks: What’s things in your mouth too; in fact, they also give

the difference? off CO2 gas. But take a look at a Pop Rocks Fizzies are also available as a label; CO2 is one of the ingredients. CO2 bubbles candy that can be popped into your are manufactured inside the candy, and as the mouth, known as Mini-Fizzies. Each sugar dissolves in the mouth, the gas is packet contains five flavors: berry, released, producing a popping sound. This is a cherry, grape, punch, and orange. You physical change: No chemical reaction here! put a single Mini-Fizzie on your tongue,

PHOTO COURTESY OF PREMIERE INNOVATIONS, INC.

The original packaging for Fizzies

Brian Rohrig is a chemistry teacher at Aurora High School in Aurora, OH. He has just written a book called 150 Captivating Chemistry Experiments Using Household Substances. This is Brian’s first article in ChemMatters.

REFERENCES Alper, Joseph. “Crazy candies!” ChemMatters, October 1993, p. 11. Lukas, Paul. “Fizziness as usual.” New York, Sept. 16, 1996, p. 50. Selinger, Ben. Chemistry in the Marketplace, 4th ed.; Harcourt, Brace, Jovanovich: San Diego, CA, 1989. Sizer, Frances; Whitney, Eleanor. Nutrition: Concepts and Controversies, 6th ed.; West Publishing: St. Paul, MN, 1994.

6 ChemMatters, FEBRUARY 1998 MysteryMatters Lindow Man— Murders in a Bog

By Lynn Sibley n May 13, 1983, Andy Mould and Stephan Dooley O were working the shredder at the Lindow Moss Company in County, England. It was their job to watch for rocks or large pieces of wood that might jam the shredder. They spotted what appeared to be a burst football and, picking it up, joked that it might be a dinosaur’s egg. As they handled it, the peat that was stuck to the “egg” began to fall away. Curious, they hosed it off, and it became clear that the object was a human skull—hair clung to the scalp, the left eyeball was still intact, and brain tissue was visible inside the cra- nial cavity. They called the police. The police were intrigued by the

discovery. When the preliminary PHOTO: ©THE forensic report found that the skull was that of a European female between the ages of 30 and 50, the for Archaeology analyzed the skull by More body parts police arrested Peter Reyn-Bardt for using a dating technique involving murdering his wife some 20 years ear- radioactive 14C and determined that On August 1, 1984, Andy Mould lier. Faced with what appeared to be the skull was not Mrs. Reyn-Bardt’s was again scrutinizing the peat as it irrefutable evidence, Reyn-Bardt con- but that of a woman who had died moved toward the shredder. He fessed that he had killed his wife, dis- about 1,750 years earlier. Based on grabbed what he thought was a large membered her, and buried her in the the strength of his confession, how- piece of wood and tossed it toward his Lindow Moss bog. Subsequently, the ever, Mr. Reyn-Bardt was convicted of partner where it fell hard on the ground, Oxford University Research Laboratory murder. exposing a well-preserved human foot. is written 406 Romans leave Britain 98 Roman historian Tacitus writes about bog bodies 700 55 BCE Romans invade Britain 230 Lindow Woman entombed in Lindow Moss 20 BCE Lindow Man entombed in Lindow Moss Beowulf On August 6, the team began to trim The Acid Test away the peat. The remains occupied a small space, 0.7 m by 0.55 m, and Turner feared he Lindow bodies did not rot in that only a portion of the body had survived Tthe peat bog. Normally a dead the peat-cutting machines. The team slid a body is broken down by bacteria in a sheet of plywood under the block of peat process called putrefaction. It didn’t containing the body, lifted it out, protected it happen in this case because of three in plastic sheeting, and drove it to the mor- important factors: The water in the tuary at a nearby hospital. The coroner bog was anaerobic (no free oxygen), placed it in a refrigerated box kept at 4 °C, which prevented bacteria from grow- the standard morgue temperature. ing; it was highly acidic (around pH The autopsy was conducted by Lon- 4), which preserved the Lindow don’s British Museum, but the coroner would Man’s skin, hair, and fingernails; and not release the body until it was proven to be it was extremely cold, which refriger- ancient. Researchers at the Atomic Energy ated his body and arrested decay. Location of Lindow Moss in Great Britain Research Establishment, using accelera- are unbalanced ecosys- tor mass spectrometry, a tems—they produce more vegeta- technique of radiocarbon The next morning Rick Turner, a tion than they decompose, causing a dating that isolates and Cheshire County archaeologist, began a buildup of material called peat. Peat search of the area. Walking along an uncut is made up of these partially decayed section of the bog, Turner noticed a flap of plants; humic and fulvic acids pro- skin jutting from a wall of peat. The skin, duced by this decay; and small coffee-colored with visible pores, was flexi- amounts of insects, algae, yeasts, ble except for the tip that had been exposed When an and fungi. This plant accumulation organism dies, to the air for several months. Turner won- replenishment of prevents oxygen from reaching dered whether it was Mrs. Reyn-Bardt or 14C stops. deeper water. another ancient body. The percentage of 14C There are different types of Turner’s discovery brought a team of steadily decreases at a known bogs, depending on weather and ter- scientists to the Lindow Moss. Turner was rate. The longer the rain, but most form in basins that organism is convinced that the body was ancient dead, the less have little or no drainage because because it was resting in undisturbed peat 14C remains. the underlying bedrock is imperme- 2.5 m below the bog’s original surface. The able. As the water level rises, vegeta- police were not so sure. tion growing along the bank drowns and decays, forming soils that dam Carbon dating incoming streams. With no flowing Fingernails still attached to the right hand counts 14C atoms, tested some bone frag- water, the soil becomes water- ments. On August 17, they announced that logged. Floating vegetation, primarily the body was at least 1,000 years old. More moss, spreads over the careful analysis later revealed that it was water like an insulating blanket. about 2,000 years old—from Celtic times. Sphagnum moss extracts positively charged ions, such as calcium and An unusual autopsy magnesium, from water in the soil On September 24, a team of archaeolo- and releases hydrogen ions. Because gists, chemists, surgeons, and others began the hydrogen ions are not flushed by the autopsy. They started with the flap of flowing water, the environment skin Rick Turner had first spotted. Using becomes extremely acidic. small brushes, scrapers, and squirts of dis- tilled water, they cleared away the peat, PHOTO: ©THE BRITISH MUSEUM removing the excess water with a dental vac-

The r 1242 Bacon describes a formula for making gunpowde 1078 Construction begins on the Tower of London 1150 Oxford University is founded 1215 Magna Carta is signed 8 ChemMatters, FEBRUARY 1998 1386 Chaucer writes Canterbury Tales uum. As Turner suspected, the lower body had been chopped off by the peat-digging Full frontal excavation of Lindow Man equipment. However, the upper intestines and stomach survived, their contents pre- served by the bog’s high acidity (see The Acid Test). When the face was cleaned, they knew for certain that the body was that of a male— the shape of the bone in the upper eye socket, the prominent mastoid bone (the bump behind the ear), and the beard were PHOTO: ©THE BRITISH MUSEUM male traits. His head slumped downward, facing his right shoulder. The right arm, in good condition, was outstretched, with four Preserved again Lindow Man’s well-manicured nails. The left forearm, in The next task was to preserve the body. Last Meal poor condition, was frayed above the wrist, Could modern technology do a better job than exposing bone. Scanning electron the acidic waters of the Lindow Moss? The he Lindow Man’s stomach con- microscopy (SEM) analysis of the beard and team decided to freeze-dry the Lindow Man. tained sphagnum moss spores; mustache hairs revealed “stepped” ends, T Freeze-drying removes moisture from organic crushed wheat, bran, and barley indicating they had been trimmed with materials by sublimation. Water is turned into grains; and mistletoe pollen. shears and not with a single blade. He was ice, then converted to vapor and removed. Electron spin resonance (ESR) naked, except for a fur armband. The fur— This method preserves the original structure spectroscopy showed that he had short (5–10 mm), ginger-colored, and and avoids excessive shrinkage. The team eaten burnt griddlecake before he round—was fox fur. His upper body muscles experimented first with pigskin. When they died. ESR can determine thermal were developed evenly on both sides which found the right method, they placed the body decomposition in organic matter by suggested, along with his well-groomed in a freeze-drying machine. When it was detecting atoms with unpaired elec- appearance, that he had done no manual removed, the body was gradually adjusted to a trons. When food is cooked, the labor. room temperature of 19 °C and a relative reactions that take place create mol- humidity of 55%. The body shrank less than ecules with unpaired electrons. The ? 5% and retained enough flexibility to be han- food’s molecular structure changes A chill came over the team as they dled easily. according to the intensity of the rinsed away more peat—this man had met a Today the Lindow Man rests in a display heat. From ESR spectra, it is possi- violent death. His skull was fractured in two case in the British Museum in London. Unlike ble to estimate the highest tempera- places, and his throat slit on the right side his grave in the bog, he lies on his back, face ture the food reached while being through the jugular vein. A leather thong dug up—his eyelids closed over empty sockets, cooked: boiled, 100 °C; baked, into his neck; he had been garroted. X-rays his lips pulled open from the autopsy. The fur 200–300 °C; or hotter, if burned. showed that his neck was broken, which armband is still wrapped around his arm, and accounted for his head’s unusual slump. the sinew garrote circles his throat. Why was the Lindow Man so brutal- ized? Anne Ross, an anthropologist who specializes in Celtic traditions, says that Lynn Sibley is a writer and former managing editor of ChemMatters magazine. aspects of his death suggest that he was a REFERENCES victim of Druidic sacrifice. One clue is that Bahn, Paul G. “Bodies of the bogs.” Archaeology, July/August 1997, pp. 62Ð67. he died a threefold death. Another clue is the Menon, Shanti. “The people of the bog.” Discover, August 1997, pp. 60Ð67. analysis of the stomach contents, which Moore, Peter; Bellamy, D. J. Peatlands; Springer-Verlag: New York, 1974. Robins, Don. “A spin through the past.” New Scientist, Feb. 25, 1996, pp. 49Ð52. contained burned cereal grains (see Lindow Stead, I. M; Bourke, J. B.; Brothwell, Don. Lindow Man: The Body in the Bog; Cornell University Press: Man’s Last Meal). Fried griddlecake was part New York, 1986. Turner, Richard; Scaife, Robert. Bog Bodies: New Discoveries and New Perspectives; British Museum Press: of Celtic rituals, Ross says, and the black- London, 1995. ened crust was fed to a sacrificial victim. Van de Sanden, Wijnand. The Bog Bodies of Northwest Europe; Batavian Lion International: Amsterdam, 1996. Werrick, Robert. “What were like, and was Lindow Man one?” Smithsonian, March 1996, pp. 146Ð47.

1984 Henry VIII dies Fleming discovers World War II penicillin 1939 1835 First documented discovered in Denmark 1687 Newton establishes his laws of motion and gravity 1850 Dickens writes 1962 Harvesting of Lindow Moss begins 1546 1590 Shakespeare begins writing plays 1807 Davy discovers sodium 1928 1963 Mrs. Reyn-Bart murdered 1477 First book printed in England 1914 World War I 1983 Lindow Woman discovered David Copperfield 1949 Orwell publishes 1984 Lindow Man discovered By Bruce Goldfarb

olor-changing Silly Big things Putty is an example in small C of a dazzling new technology that changes the packages way we see things. In the Microencapsulation was past few years there has developed in the late 1930s at been an explosion of color- the National Cash Register PHOTOS BY MIKE CIESIELSKI changing products—coffee Company and introduced in mugs, T-shirts, pencils, carbonless paper in 1954. The stickers, and even battery testers. for a length of time. Because of this color paper is coated with microscopic spheres Many of these products use ther- change, hospital workers can tell just by look- containing chemicals that are pigment pre- mochromic pigments and dyes that change ing at an item whether it has been sterilized. cursors—two colorless substances that turn color according to temperature. Simple irre- The pigments used in Silly Putty and dark when combined. The weight of a pen versible thermochromic pigments have been similar products are different from these ther- crushes the microcapsules, allowing the around for a long time. For decades hospitals mochromic products. They include a chemicals to mix and make colored ink. have used indicator strips or tape that devel- “reversible” microencapsulated pigment that ops a dark stripe when exposed to steam heat cycles from a color to colorless and back again. This seemingly amazing stunt has a After sterilization melamine surprisingly simple explanation: The pig- formaldehyde ments work because waxes and fats are methyl stearate opaque when solid and transparent when liquid; just look at the clear melted wax that drips from an opaque candle.

Before sterilization

Hospitals use color-changing indicator strips on ILLUSTRATIONS BY CESAR CAMINERO equipment and supplies so that they can tell Carbonless paper uses microencapsulation whether the item has been sterilized or not. technology.

10 ChemMatters, FEBRUARY 1998 Microencapsulation is used in every- The next wave of development will take thing from scratch-and-sniff samples to color-changing pigment from a novelty to a deodorants. In the case of color-changing security device. There is growing interest in pigments, the microcapsules are composed the potential for color-changing inks among of melamine formaldehyde—the same mater- security and law enforcement agencies, says ial as Formica—filled with a lipid (a fat) such Fred Davis, president of Davis Liquid Crystals PHOTO COURTESY OF BINNEY & SMITH as methyl stearate, according to Lyle Small, (San Leandro, CA). Because color-changing president of Chromic Technology, Inc. (Col- ink is more costly than regular inks, it is usu- orado Springs, CO). ally used as a “spot” color in a small area or The microcapsule contains a dye that is a stripe. You can make copy-proof paper by barely visible when the lipid is liquid but is treating it with a pigment that is colorless on vividly bright when the methyl stearate solidi- the paper but turns dark upon exposure to fies. A jar of pure microcapsules has a pale the heat of a photocopy machine. After an color. When the pigment is diluted in an ink or original is removed from paint medium and spread in a thin layer dur- the photocopier, the dark- ing printing, it becomes essentially invisible. ened area returns to col- By altering the combination of lipids in orless, but a copy shows the microcapsules, color-changing pigments the darkened area; there- can be made to cycle at almost any chosen fore, you can tell very eas- temperature, within a range of only about ily whether you have an 5 °F. Like all lipids, color-changing microcap- original or a copy. sules are subject to oxidation, ultraviolet radi- Color-changing pig- ation, and other degrading effects. Small says ments are beginning to be that the reaction may eventually stop cycling, used in passports, certifi- but under most conditions, it will continue cates, licenses, tickets, indefinitely. and other official docu- ments. It is going to make From novelty to it much more difficult to get a fake ID, for example. Color-changing Color-changing Silly Putty security does everything the original ink is “quick and easy to add” and difficult to does—and more! Color-changing microcapsules come in counterfeit, says Davis. However, “no tech- a palette of about a dozen colors. Two differ- nology is effective forever. The bad guys ent dyes are typically used in printing and catch up eventually,” he says. other applications—one is a permanent ink and the other a translucent color- changing pigment. COPY COPY COPY For example, if red Mainland Mainland ink is mixed with a ool D ol D blue color-changing igh Sch iploma igh Scho iploma H By Virtue of the State of Florida H By Virtue of the State of Florida pigment, it will this certifies that this certifies that appear purple when Ocsar Watson Ocsar Watson cool. As you warm has graduated. Photocopier has graduated. it, the blue color COPY COPY COPY melts away, turning the purple to red. Original Photocopy Small’s cre- ation of a thermochromic pigment in a sturdy microcapsule led to the development of inks Bruce Goldfarb is a science and medical writer in Baltimore, MD. His article “CO control: On that could be used on standard printing the street, in the house, where you live” appeared in the MysteryMatters department of the presses. These color-changing inks have October 1997 issue of ChemMatters. opened new avenues of creativity that are REFERENCES limited only by the imaginations of designers Bide, Martin. “Hot shirts.” ChemMatters, October 1992, pp. 8Ð11. and artists. Marsella, Gail. “Silly Putty.” ChemMatters, April 1986, pp. 15Ð17.

ChemMatters, FEBRUARY 1998 11 A Successful Failure

illy Putty—one of America’s greatest toy-marketing suc- Elastomers cesses—started out as a complete failure. During World War An elastomer will be rubbery (left) if it has S many cross-link bonds. If it has few cross-link II, the United States faced a severe rubber shortage, bonds (center), the elastomer behaves like a which prompted industry to launch research liquid. When the cross-link bonds are weak efforts to develop a synthetic rubber substitute. and easily broken (right), elastomer behavior is described as dilatant. In 1943, chemical engineer James Wright was hard at work on the rubber problem at a General Electric (GE) laboratory. He mixed der, mingling together like a bowl of boric acid and silicone oil in a test tube, which cooked spaghetti. Its behavior is deter- was then heated. When polymerized, the com- mined by the number of chemical bonds linking pound formed a gooey plastic. The material could be neighboring molecules. If the molecules have a lot of cross- easily molded, but refused to keep its shape. It link bonds, the material will be quite rubbery. If there are only a few PHOTO COURTESY OF BINNEY & SMITH flowed like a liquid but would snap if pulled quickly. cross-linking bonds, the plastic molecules easily slide past each other You could roll it into a ball and bounce it off the floor: Interesting and flow like a liquid. stuff, but worthless as a rubber substitute. Usually, the cross-links in polymers are strong covalent bonds. GE sent samples to engineers and scientists, hoping that some- But Silly Putty has weaker coordinate bonds (bonds in which both body might think of a use for this material—and perhaps make a profit electrons are donated from one of the two atoms)—bonds that are for the company. Dozens of the most creative scientific minds could easily broken. If you pull Silly Putty slowly, it will flow and stretch. Pull not think of a single practical use for Wright’s plastic. it faster, and Silly Putty will snap right in two. Liquidlike materials that act like a solid under short-term stress are described as dilatant. After Hodgson’s death, the rights to Silly Putty were bought by OH CH3 CH3 CH3 Binney & Smith, makers of Crayola crayons. The pink plastic is a fix- HO—B—OH + — O—Si—O—Si—O—Si—O— ture in American culture. More than 200 million eggs of Silly Putty have been produced since 1950. Silly Putty is recognized in 97% of American homes and has been purchased by almost 70% of house- CH3 CH3 CH3 holds, according to Binney & Smith marketing information. Boric acid Silicone oil Silly Putty was a familiar pink color until 1990, when Binney & Silly Putty ingredients Smith unveiled fluorescent colors to celebrate its 40th anniversary. Glow-in-the-dark Silly Putty was launched the following year. Binney & The bouncing blob was passed around as a novelty in industrial Smith introduced color-changing Silly Putty in 1995. and scientific circles, eventually falling into the hands of a toy shop Color-changing Silly Putty uses a nifty chemical trick that is owner Ruth Fallgatter. An advertising consultant, Peter Hodgson, sug- more complicated than other color-changing inks but still based on gested that Fallgatter market the material as a toy for adults. In 1949, melting points. The Silly Putty contains microcapsules 15–35 microm- she bought a quantity of the goop, packaged small pieces, and sold eters (µm) wide that hold a two-part dye and a temperature-sensitive them for $2. The following year, when she lost interest in the plastic, solvent. The dye consists of two chemically bonded molecules. When Hodgson decided to market it himself. Hodgson borrowed $147 to the Silly Putty is warmed, the solvent melts and separates the dye buy a batch of the goop, which he packaged in inexpensive plastic molecules so they no longer create a color. eggs. He chose “Silly Putty” from a list of a dozen names and sold the One variety of Silly Putty turns from orange to yellow when one-ounce wad for $1. warmed; the putty is colored yellow and mixed with microencapsu- Silly Putty made its debut at the 1950 International Toy Fair in lated red pigment. When the Silly Putty is cool, you see the yellow and New York. A full-fledged fad emerged after Silly Putty was mentioned red pigments as orange. As you play with the Silly Putty and warm it in The New Yorker. Within three days, Hodgson received more than a with your hands, the red melts away, leaving only the yellow. quarter-million orders. There’s a lot of science packed in a $1.50 plastic egg, proving Silly Putty is an elastomer, a substance that regains its original that you can learn from failure. When Peter Hodgson died in 1976, he shape after being stretched or deformed. This is what gives Silly Putty left a $140 million estate—a tidy fortune for selling a completely use- its bounce. The molecules that make up the plastic are long and slen- less product.

12 ChemMatters, FEBRUARY 1998 By Harvey Black dards, about 100 places in the United was first described by California Institute of t’s a hot, sticky July day in Chicago. States were identified as nonattainment Technology scientist Arie J. Haagen-Smit Pedestrians trudge through the city’s areas: Ozone levels in their air exceeded the more than 40 years ago. However, atmos- Iclammy streets, mopping their brows standards. Chicago was one of these areas. pheric chemists have only recently begun to with handkerchiefs. The air seems heavy The new standards have not been in place grasp the sometimes maddening complexity and unpleasant. It’s a perfect day for ozone long enough for new nonattainment areas behind the spawning of this noxious com-

(O3). In the air we breathe, ozone—the to be named. pound. product of volatile organic compounds Understanding what’s behind ozone formation pushes the limits and the (VOCs) mixed with nitrogen oxides (NOx) EPA wants substantial cuts in NOx in the presence of warm sunlight—makes emissions in 22 states. imagination of scientists, notes William life unpleasant. Chameides, who directs Georgia Tech’s Temperatures in the 30s on the Cel- School of Earth and Atmospheric Sci- sius scale (90s on the Fahrenheit scale) Wis. ences. Although the ingredients of ozone 35% Mich. N.Y. are needed to supply heat for ozone for- 19% Mass. seem simple, they are anything but. 32% 32% Pa. Hundreds of VOCs can be involved in mation, says Michael Koerber of the Lake Ill. Ind. Ohio 32% R.I. 19% 38% 42% 43% Conn. 21% ozone formation, and that means a Michigan Air Directors’ Consortium. Mo. W. Va. N.J. 25% 43% Ky. 44% Va. Del. 28% That’s why ozone isn’t a winter problem, 40% 21% Md. 36% whole set of complex chemical reactions Tenn. N.C. D.C. 9% going on. “We don’t understand the even though winter days can be very 35% 34% S.C. sunny. Ozone makes breathing more diffi- 31% chemistry of every one of those com- Ala. Ga. cult. In fact, when there’s too much, local 36% 35% pounds,” says Chameides. “Each one Requested NOx reductions governments issue ozone alerts to warn from projected 2007 levels contributes to ozone formation in differ- 40% or more ent ways depending on the specific envi- people with breathing disorders such as 30 to 39% asthma to stay inside. 20 to 29% ronmental conditions surrounding it.” 19% or less Last year the Environmental Protec- Not required to Furthermore, “All those compounds Source: Environmental Protection Agency reduce emissions tion Agency (EPA) tightened its ozone influence one another in nonlinear regulations, further curtailing the amount ways,” says Jay Odum of Georgia Tech. allowed in the air. Those limits can affect Understanding the chemistry of ozone “You can’t change just one and get a corre- anything capable of producing emissions is crucial to controlling it, and ozone chem- sponding change in the way that ozone is that increase ozone in our atmosphere, istry is nothing if not complex and poten- formed.” Moreover, notes Odum, the num- such as trucks, automobiles, power plants, tially confusing. The problem of ozone, or ber of chemical products created when a and factories. Under previous EPA stan- photochemical smog, as it was once known, VOC breaks down to form ozone can be

ChemMatters, FEBRUARY 1998 13 processes and oxidizes over time to carbon nationwide. Over the past couple of years, the dioxide and water. “What’s happening with Ozone Transport and Assessment Group, an air pollution is we dump a lot of reduced East Coast consortium, has examined compounds into the atmosphere in a concen- weather conditions, such as wind move- trated form in a given location; that causes ments, temperature, and humidity, in an the oxidation process to speed up. In the effort to understand how ozone-causing pol- process, we produce ozone,” he says. There- lutants travel through the air and bring ozone fore, ozone formation is an acceleration of a pollution to areas several hundred miles away normal process. from where they are emitted. The third major player in ozone creation Obviously sunlight can’t be controlled to

is NOx. Whereas VOCs and sunlight are the limit ozone. Therefore, efforts to rein in ozone fuel for ozone, NOx is the “catalyst” that leads center on limiting VOCs and NOx. VOCs come to ozone, explains Chameides. Two forms of from two major sources—human activity

NOx, nitric oxide (NO) and nitrogen dioxide (anthropogenic) and nature (biogenic). (NO2), are produced by the combustion of Anthropogenic VOCs result from manufactur- gas and oil, which means cars and trucks put ing processes as well as car and truck fuel it into the air. combustion. Biogenic VOCs, such as iso-

Keeping track of NOx is tricky, explains prene and terpenes, are produced by plants Barbara Finlayson-Pitts, a chemist at the Uni- and trees. NOx is a bit simpler: It comes from versity of California-Irvine. “The major form smokestacks and, as mentioned before,

of NOx that comes from combustion is NO. tailpipes. To produce ozone, it has to be oxidized to Here’s where limiting ozone can make

NO2, which then photolyses to give an oxy- air pollution controllers sprout gray hair. gen atom, which leads to more ozone.” At the What researchers have found over the years You can smell ozone in the air around welding. point where NO is being emitted, it will react is that a kind of give-and-take occurs enormous. Consequently, notes Chameides, scientists must use mathematical models— sets of equations—to approximate what they Air Pollution Stems from think is going on. Sophisticated though these Natural and Anthropogenic models may be, they are still at least one step Sources removed from reality. Key to setting off ozone formation is the OH, or hydroxyl, radical. The OH radical is a free radical—it has one unpaired, or free, UV Radiation electron in its outer shell—and therefore it can undergo a process called energetic rebounding. “It’s going to grab an electron from another chemical and, in that process, it’s going to cause a chemical reaction,” says VOCs VOCs VOCs NOx NOx VOCs Chameides. “Free radicals are very reactive things in the environment.” What the OH radical is doing, says Chameides, is enhancing what the atmos- Vegetation Industries Transportation Biogenic Sources Anthropogenic Sources phere normally does. Our atmosphere is oxy- gen rich—about 20% oxygen. So if compounds go into the atmosphere with little with oxygen to form NO2. However, air between NOx and VOCs. Consider, for exam- oxygen, our atmosphere kindly offers it to masses move. “As the NO2 goes downwind, ple, the city of Atlanta, GA. Not only does it them. it clobbers the next guy [with ozone]. It’s have lots of VOCs produced by cars and fac- VOCs don’t have much oxygen, meaning transferring the problem elsewhere,” she tories, it has forests of oak trees emitting iso- says. Finlayson-Pitts points to California as a prene. In short, it has a high VOC/NO ratio. they are in a reduced state, so they are per- x prime example of this phenomenon. Although Early attempts at controlling ozone in Atlanta fect candidates to receive oxygen donations. NO emissions are high in Los Angeles, the focused on trying to control VOCs from Chameides emphasizes that oxidation of x ozone problem is downwind. human activity. It didn’t work. Nature pro- reduced compounds is an entirely natural Numerous organizations from the public duced so many VOCs that the amount regula- process. For instance, methane is put into the and private sectors are studying ozone tors took out of the air was equivalent to a air naturally as part of decomposition

14 ChemMatters, FEBRUARY 1998 Where Ozone is Good for You 50 lthough ozone near the ground can make life unpleasant, when it’s between 10 and 30 A miles above us—in the stratosphere—it’s important, if not downright vital to our 30 lives. It prevents harmful forms of solar ultraviolet (UV) radiation (such as UV-B, which can 20 cause skin cancer) from reaching the earth. This high-altitude ozone is generated when sun- light hits molecules of oxygen (O ), creating two oxygen atoms. These single atoms can then 2 10 combine with oxygen molecules to form ozone (O3). The sunlight or UV radiation responsi- ble for splitting the molecules of oxygen is at wavelengths of <240 nanometers (nm). Ozone, 5 Urban O3 max however, is unstable and is itself easily broken down when free radicals such as the OH radi- (km) Altitude cal, bromine, or chlorine, which occur naturally in the stratosphere, combine with it. 3 Rural O3 max But, as was shown by Nobel Prize-winning scientists F. Sherwood Roland and Mario 2 Molina, humans have had an important role in breaking down the protective ozone of the 1 stratosphere. Chlorofluorocarbons (CFCs), synthetic chemicals designed to be coolants, 10 100 1,000 10,000 have leaked into the stratosphere. There, high-energy UV radiation breaks them down, free- ing the chlorine, which can destroy ozone. The amount of chlorine generated this way dwarfs Ozone (ppb) the naturally occurring amount in the stratosphere. CFCs in the lower atmosphere are inert.

Their only activity is to slowly migrate upwards, where they can do damage. SOURCE: GEORGIA INSTITUTE OF TECHNOLOGY OF INSTITUTE GEORGIA SOURCE:

few buckets of water from the ocean. It didn’t Scientists such as Finlayson-Pitts and toluene in one city might be different in make much difference. Odum argue that for ozone to be effectively another,” he says. “It depends on what time

Put in more scientific terms, when the limited, both strategies—NOx control and of day the compound is released—in the mid-

VOC/NOx ratio is high, NOx is the limiting fac- VOC control—must be used. If VOCs are to dle of the day, when ozone is reaching its tor. Control NOx and you might be able to be controlled, the “different propensity” of maximum value, in the morning, throughout limit the production of ozone. Reverse the sit- each to form ozone—their reactivity—must the day, and so forth.” uation—a low VOC/NOx ratio—and the oppo- be considered, says Odum. But control of Teasing out the chemical complexities of site strategy should work. VOCs are the those VOCs depends on more than just ozone is a demanding and frustrating effort, limiting factor; therefore, regulations control- knowledge of the particular compound. “The but understanding the complexities behind its ling them should reduce ozone. problem is that reaction conditions for, say, formation is crucial to controlling it and hav- ing clean air.

Ground-level pollution from all sources can be a problem around major cities.

REFERENCE Raber, Linda. “EPA calls for NOx emissions cuts.” Chemical & Engineering News, Oct. 20, 1997, p. 14.

Harvey Black is a freelance science writer living in Madison, WI. His article “Surprising Citronella” appeared in the February 1997 issue of ChemMatters.

PHOTO COURTESY OF NATIONAL CENTER FOR ATMOSPHERE RESEARCH/ UNIVERSTIY FOR ATMOSPHERIC RESEARCH/NATIONAL SCIENCE FOUNDATION

ChemMatters, FEBRUARY 1998 15 by Robert Becker Use the clues to fill in the crossword puzzle Kirkwood High School using the names of 15 different elements. Elemental Some of the clues contain a double-entendre. Kirkwood, MO Circle all that you find. For example, This metalloid is used in transis- tors—think about that as you drive along our Punishment scenic highways listening to your radio! The element is arsenic and the double-entendre is “our scenic,” which sounds like arsenic. (Answers are on page 3.)

6 1. Without this noble lightweight, scuba divers would be bent out of 1 2 shape and doctors might be unable 5 to heal them. 2. Critical mass of this fissionable 3 material can blast you to the outer limits of the solar 4 system! 3. Nothing is as effective as stating the obvious— with less than 1 ounce of this halogen on Earth, 7 it’s not very abundant. 4. Cinderella owes her good fortune to this semi- conductor. 8 5. Has your car been acting up? You may want to check the antifreeze, oil, or gasoline. 6. Hamlet’s soliloquy pondered 9 10 11 whether or not this metalloid was diatomic. 12 7. Man can easily survive 13 (and so can woman) without Ag or Au, but 14 don’t take away this trace dietary mineral. 8. Although this is the most abundant metal in the 15 Earth’s crust, all you minimal waste advocates have to remind everyone to stop treating it like trash.

9. This alkaline earth metal is toxic by itself, but 12. This metal is in stained glass windows and old paint, but not in doctors instruct patients to drink a thick shake of pencils, as some might lead you to believe. its sulfate helping to prevent burying them. 13. Dairy farmers see milking machines as 10. This metal is named for its sky blue spectral lines quick extractors of this alkaline earth and is used in atomic clocks that are accurate to metal, but I bet the cows see them differently. 1 s in 60 yrs. 14. Snips can cut this metal into tiny pieces. It is used 11. When the Lone Ranger photographs his for solders and soldiers. horse’s fillings in the mirror, he must 15. Nick-named “quick silver,” this dense and toxic liquid metal is wonder why this metal is still consid- used in barometers and electrical switches. It’s hard to imagine a ered second best by most athletes. more curious metal.

16 ChemMatters,FEBRUARY 1998