December, 1991

sDECEMBER 1991

" ...they recovered some camerasfrom his locker but, when they triedto match the serial numbers withthe school r.corlb, th.y found thatthe cameras' numbers had beenfiled off. That's when the principalcall.d m•...IIMystery Matterspage 12

1616161616

1212121212

8 8 8 8 8

4 4 4 4 4Peanut BrittleHere’s how you can make edible “glass” from sugar.

Homeopathy, Cure or Quackery?If all the molecules are gone, can the drug take away your headache?

MysteryMattersStolen CameraHe thought that if he grabbed the cameras and filed off the serial numbers, no onecould trace them. Wrong!

Gift of MintUndiscovered medicines and pesticides may be right under your feet.

The Puzzle PageRiddled with PunsThe chemical elements were never so punny.

1515151515

December 1991

PEA~OTBft~ITT~[~E ___

By Elizabeth Catelli

Whack! The clear solid shatters intosmall pieces when dropped onto atable. What is it? It looks like glass,and it certainly breaks like glass, butit tastes sweet. It's peanut brittle!

It is no accident that peanut brittleresembles light brown glass. It is anamorphous solid, also known as aglass. Many common solids are crys­talline, which means that theirmolecules are arranged in an orderlypattern that resembles a three­dimensional grid. In contrast, themolecules of an amorphous solid arerandomly dispersed. (Amorphousmeans without shape, or lacking adefinite pattern.) Lollipops and LifeSavers are amorphous candies;fudge and fondant (creamy candy orfilling) are crystalline. The differencein texture is due to the way they aremade.

4 CHEM MAnERS, DECEMBER 1991

Sugar and spiceCandies are chiefly solutions of ordi­nary table sugar, sucrose, andwater.Other ingredients such aschocolate, cream, glucose, and fla­voring agents may add flavor, tex­ture, and enjoyment, but the struc­tural characteristics are determinedmainly by the relative amounts ofsucrose and water and the size of thesucrose crystals. The cook must usean excess of water in the initialsucrose solution to be sure that all ofthe sucrose dissolves. The solution isthen heated to boil off the excesswater. When it is removed from theheat, the solution cools and becomessupersaturated, that is, it containsmore sugar than can normally dis­solve at the lower temperature. Youmight expect that sucrose would startto precipitate or crystallize out of thesolution at this point, but if no seedcrystals of undissolved sugar are pre-

sent, the solution can be cooled con­siderably before crystallization takesplace.

To form crystalline candy, thesolution is cooled well below its nor­mal crystallization temperature, thenwhipped very hard to form manymicroscopically small crystals. Inmaking amorphous candies, howev­er, the object is to have NO crystalsform. To bring this about, it is neces­sary to heat the sucrose solution untilnearly all of the water has evaporat­ed. When the solution is greater than95% sucrose, it becomes very thick,or viscous, and movement of thesucrose molecules is restricted. Theycannot move into the orderly arraynecessary to form a crystal lattice. Ifthe solution is cooled quickly, themolecules are frozen where they are,forming a glass-like amorphous solid.

This process is aided by adding asmall amount of corn syrup, which

contains another sugar, glucose.Because glucose molecules are thewrong size to fit into the sucrose crys­tal lattice, they can't add to the crys­tals. They may, however, join otherglucose molecules to form longchains which block the motion ofsucrose molecules and prevent themfrom joining a sucrose crystal.

CH20HIC-O °

H / \ \ H HOCH2 ./ "'-. H\ H I \7 "'-.'C C C C, \ OH H / ""'0/ \ H HO/ \

HO C-C C-C CH20H\ , \ I

H OH OH H

Sucrose

Figure 1. Sucrose, ordinary table sugar, is the major ingredient in candies. Byweight taffy is about 40% sucrose and hard candy is about 80%. Sucrosemolecules can nest together (A) to form sugar crystals, but large crystals areundesirable because they feel grainy in the mouth. To prevent the growth oflarge crystals, candy makers add glucose and fructose which cannot nest withsucrose because their molecules are shaped differently. At B, a molecule offructose blocks the growth of the crystal.

Glucose

polymerizes into brown pigments thatadd flavor and color to the candy.This process is called caramelization(see Figure 2).

If heating continues longer, thecolor changes from golden brown todark brown. A variety of products areformed as sucrose breaks down intosmaller organic molecules that arenot sweet and may have unpleasant,scorched flavors. If all the hydrogen

A

molecules are split in this way. Fruc­tose molecules freed by hydrolysismake the candy sweeter, but maykeep it from hardening as the candymaker would like. Heating the sugarrapidly keeps the number of hydro­lyzed molecules to a minimum.

Above 160°C different chemicalreactions occur. Glucose loses twowater molecules and rearranges toform hydroxymethyl furfural, which

Our favorite compoundMost of the foods we eat are mixturesof chemicals, but sucrose is a purecompound-the most Widely pro­duced organic compound in theworld. Plants produce sucrose as anintermediate product of photosynthe­sis. It seems that plants producesucrose in order to have a stable wayto transport sugar from the leaves,where it is made, to other parts of theplant. Other forms of sugar are toosusceptible to breakdown byenzymes for this purpose. The mainsources of sucrose are sugar cane,which has been grown since 6000B.C., and sugar beets, which werediscovered in the 1700s.

Sucrose is a disaccharide, a dou­ble sugar. It consists of one moleculeof the monosaccharide glucose andone molecule of another monosac­charide, fructose (see Figure 1).These monosaccharides are isomersof one another-they have the sameformula, but different arrangement oftheir atoms. This gives them differentproperties. Fructose, for example, issweeter than glucose and dissolvesmore easily in water.

Animals cannot absorb sucrosewithout separating it into its compo­nent monosaccharide in a reactioncalled hydrolysis.

C12H22011 + H20 ~ CSH 120 S+ CSH120 Ssucrose glucose fructose

In animals hydrolysis is catalyzedby the enzyme invertase. In thekitchen, a solution of sucrose can behydrolyzed by heating it slowly in thepresence of acid. During candy mak­ing, a certain number of sucrose

CHEM MATTERS, DECEMBER 1991 5

320 Boiling point (OF)

300

280

260

240

220

20 40 60 80 100

Percent sugar (by weight)

perature; is 250()F,g~Od fornougatandmarshmall~ws.

• Finally, if you find it doesootform a ball, but pulls fromtne panas thin, brittle threads that"crack"when dropped into the water, thenthe temperature is 295 OF, whichis used for butterscotch and brittle.

Playing hard ballEach type of candy requires cook­ing the sugar solution to a particu­lar temperature. As the sugar con­centration of the boiling solutionpasses 60%, the temperaturebegins to increase qUickly (seegraph). Experienced candy mak­ers can tell the temperature of acandy solution without a ther­mometer. They drop a ball of thehot solution into cold water andcheck its consistency-a tech­nique that has been used bycooks for many years that is accu­rate to within 5 OF. First, a smallamount of boiling syrup isremoved from the pan, thendropped into a cup of cold water.• If you find a "soft ball," whichholds together but flattens whenremoved from water, the tempera­ture is 235 OF. This is suitable forfondant and fudge.• If you find a "hard ball," whichretains its shape when removedfrom water, this means the tem-

Elizabeth Catelli has degrees inchemistry and science education. Sheteaches high school chemistry andphysics in Southington, CT.

and oxygen are removed from thesugar, only carbon is left-an expen­sive and time-consuming way tomake charcoal. Ideally, peanut brittledoesn't go that far. It is golden brown,clear as glass, and delicious.

Figure 2. When sucrose is heatedabove 160 DC, its molecules rearrange,give off some water as steam, andform hydroxymethyl fUrfural, above.This molecule joins with others toform various larger molecules. Theresulting mixture of large and smallmolecules is responsible for the colorand flavor of caramel.

o~ /0"",/c-c~ /lC-CH20H

H C-C

Hydroxymethyl fUrfural

ReferencesFessenden, R. J.; Fessenden, J. S. Organic

Chemistry: Willard Grant Press: Boston,1982;pp.838-39.

Grosser, A. The Cookbook Decoder, orCulinary Alchemy Explained; BeaufortBooks, Inc.: New York 1981.

Hoseney, R. C. "Chemical Changes inCarbohydrates Produced by ThermalProcessing"; J. Chern. Ed. 1984, 61(4),308-12.

Lehniger, A. L. Principles of Biochemistry;Worth Publishers: New York, 1982; pp.284-87.

McGee, H. On Food and Cooking; CharlesScribner's Sons: New York, 1984; pp.395-417.

McWilliams, M. Food: ExperimentalPerspectives; Macmillan: New York, 1989;pp.138-48.

Medved, E. Food Preparation and Theory,Prentice Hall: Englewood Cliffs, NJ, 1986;pp.354-59.

6 CHEM MATTERS, DECEMBER 1991

.........'",'::: ::<.; ~~~)

:~: ',' :: .>. '.::::}" '.' .. ' . - .•••• • ,' 0 .. o.

o •• ". '0 ':.',::.~. ::. '. . .. ~ .• ••••• 0 :.,:.. ' " ",". ·°'0........

J' ,', ••••

0.... ::0:.. ', ..'. '.

.., .

" ":#...

ii.~;«~•

3. Use a candy thermometer to tell when the solution issufficiently concentrated. Cooking too long can burn thecandy; not long enough produces a sticky candy thatnever hardens-somewhat like caramels, only worse.4. Place the sucrose, water, and corn syrup in a heavy­bottomed pan so the solution will cook evenly without hotspots. Begin heating; stir steadily so the solution heatsevenly.5. When the solution boils, cover the pan with a lid forthree to five minutes. Steam will condense on the lid andwash any undissolved sugar crystals from the sides ofthe pan into the solution where they will dissolve.

Sugar is hygroscopic-itabsorbs water from the air.While you are trying to boil thewater out of the solution, humidair can be putting it back in!

2. Safety check: Wearoven mitts to protect yourhands. Fasten back longhair, and wear eye protec­tion. Be sure your workingarea is clean.

1. If possible, do your candymaking on a dry, cool day.

This stuff is so sticky it's death to fillingsand braces.

Use a wooden spoon. Wood is a poor con­ductor of heat ... it won't burn your hand.

Candy solutions get muchhotter than boiling water,and they stick to the skin.

Making peanut brittleIngredients:225 g sucrose118 mL water118 mL corn syrup (glucose

solution)200 g peanutssheet of aluminum foil,

about 25 cm by 50 cm30 g margarine

6. Remove the lid and continueboiling the syrup until the temper­ature reaches 290 of (144°C).While the syrup is boiling, spreada thin layer of margarine on thealuminum foil. Experienced candycooks can tell the temperature by"playing hard ball" (see box). Therest of us need the candy ther­mometer.7. As soon as the syrup is ready,add the peanuts, stir, and spread ~

the mixture on the aluminum foil.Work qUickly-the candy will start . / rr;r~to harden immediately. It's a thin ~~T"'" V? :/?,,~ :.-1'"candy because, when it's spread I;; ~' I / ..:-,

out, it has a lot of surface area, Zp; .~. I :'~ •

which lets it cool quickly so it'll be \0-: ,.;.. .--:-,.;..~: . , ""\/..." .'"'\amorphous. Enough talk ... time 'C" .... ":' • "I •

to eat! ~.~~~...~~~=-- .a-4-------"""""'~

•

CHEM MAnERS, DECEMBER 1991 7

fiOMEOPAT........I=t.......Y _

In the 18th century, when most medicines were made from plants, the homeo­pathic use of natural products became popular. To recover from a fever-accord­ing to the homeopathic principle-you should take something that causes fever.Homeopathic physicians also believed that when a natural product is diluted withwater or alcohol it becomes more effective.

Cure or Quackery?By Bruce Goldfarb

When you're sick with a sore throat,the doctor may take a swab of yourthroat cells to find out what bacteriaare causing the illness and prescribean antibiotic that kills the germ. That'sthe way most traditional medicineworks-determine what's wrong, andcorrect the problem. Homeopathyclaims to heal by radically differentmeans.

Homeopathy was founded in thelate 18th century by a German physi­cian, Samuel Hahnemann. Beforeantibiotics and painkillers, medicineinvolved such harsh treatments asbloodletting, blistering mustard pIas­ters, and enemas to purge the diges­tive tract. Not surprisingly, manypatients died. Hahnemann developeda new approach that followed the phi­losophy simila similibus curantur,meaning "like cures like." For exam­ple, a practitioner of homeopathytreats a fever with a substance thatcauses a mild rise in body tempera­ture. The underlying theory, home­opaths say, involves a sort of "bodilyresonance," similar to the way a Cnote struck on a piano makes anotherC string vibrate. Inducing a mild stateof disease, according to homeopathictheory, triggers the body's naturalhealing powers.

Homeopaths also believe that themore dilute a drug, the greater itspotency. This violates the principle ofthe dose-response relationship,which states that the larger the doseof a drug, the greater its effect. Forhomeopathy to work, "the whole basisof modern pharmacology would haveto be turned around," says VeroTyler, Ph.D., former dean of the Pur­due University School of Pharmacy.

Beyond AvogadroHomeopathic remedies are preparedby a ritualized process that makesthem extremely dilute. Most homeo­pathic remedies are so dilute that the

8 CHEM MATTERS, DECEMBER 1991

dilution factor exceeds Avogadro'snumber. This means that the solutionhas been diluted to such an extentthat it's unlikely that a single moleculeof the drug is left in a dose ofmedicine (see box, "Serial Dilution").Despite the apparent absence of anyactive ingredients, homeopathsbelieve that something, some sort ofmolecular "memory" of the drug,remains in the solution.

"We don't know exactly why home­opathy works," says Dana Ullman,

author and president of the Founda­tion for Homeopathic Education andResearch. "There is a great dealabout nature that is befuddling andmysterious."

Critics of homeopathy say that theremedies are too dilute to work bychemical means, and that they can'twork by any known physical process.In short, critics charge, homeopathsare giving nothing more than inertmaterial, and any perceived benefit iscaused by the placebo effect (see

•

Today, oscillococcinum® is one of the most popular homeopathic remedies sold.The instructions read: Natural relief from symptoms of flu such as fever, chills,body aches and pains. The active ingredients, Anas Barbariae Hepatis and CordisExtractum have been diluted homeopathically 200 times before being impregnatedon the tiny sugar pellets. Take one tube of pellets at onset of symptoms andrepeat every six hours. The instructions sound clear and conventional, but theextreme degree of dilution, 200C, guarantees that the package does not containeven a single molecule of the active ingredient. Retail price for three tubes: $6.39.

•

box, "The Placebo Effect").One of the most controversial

aspects of the issue is the method bywhich .homeopathic remedies are pre­pared. After each dilution stage, thesolution is forcibly shaken by a pro­cess called succussion. Proponentsclaim succussion is very important,that simply diluting a drug to anextremely weak concentration does

not work. Shaking the solution, theysay, creates a molecular impressionof the drug on the water or alcoholdiluent. As a result, the diluent keepsa "memory" of the drug that haseffects on the body similar to the drugitself.

Mainstream scientists say succus­sion is nonsense. "There's no scientif­ic evidence that it has any effect at

all," says Tyler. Shaking the solutionhas "no proven value over adding asmall amount of drug into an ocean ofwater."

Advocates say that homeopathyhas been proven to work in numerousstudies-even on animals and tissuecultures. In July 1988, the prestigiousscience journal Nature published theresults of a study by JaquesBeneviste of the University of Paris.Beneviste reportedly observed thereaction of white blood cells to an anti­body solution that had been diluteduntil the ratio of antibody to water was1:1 ,200,000,000,000. Because mereblood cells can't be aware that theyare being studied, and are thereforeimmune to the placebo effect, the find­ings were hailed as proof that home­opathy works.

After the report was published, ateam of investigators went to Paris todouble-check Beneviste's work. "Wehad him repeat the experiment sixtimes. The three times that it was dou­ble-blinded, it didn't work," saysJames Randi, a magician who was amember of the team who investigatedBeneviste's experiments. Randi, whoperforms under the name of "AmazingRandi," is a board member of theCommittee for the Scientific Investiga­tion of Claims of the Paranormal.

Scientifically repeatable?Critics charge that homeopathy hasfailed to pass modern scientific stan­dards. "In order for something to beestablished, it has to be replicated byother experimenters," explains Dr.Stephen Barrett, author of HealthScams, Schemes and Frauds. "Virtu­ally every research paper that's beenpublished so far has been sloppilydesigned. There have been so fewwell-designed studies that you don'tknow what it means when one or twoget reported. We don't know howmany negative studies were neverreported."

"There's a part of healing that can'tbe measured by science yet," coun-

CHEM MATTERS, DECEMBER 1991 9

ters Dr. Jaquelyn Wilson, a traditional­ly trained physician who has includedhomeopathy in her practice for 14years. Dr. Wilson is one of about 500traditionally trained medical doctors inthe United States who also practicehomeopathy.

"We aren't working on a molecularsystem," Dr. Wilson says. "Homeopa­thy works by some sort of energy thatcan't be measured by scientificinstruments."

In recent years, interest in home­opathy has grown because it is a low­tech, apparently more natural alterna­tive to expensive and intensivetraditional medical care. Although it isprimarily used to treat such minorproblems as earaches, critics say it isharmful because some homeopathsclaim it is effective against serious ill­ness such as cancer and AIDS.

But if homeopathy is only appliedto minor problems, proponents argue,how can it be harmful? "Most peoplewho have been helped by nontradi­tional medicine have recovered spon-

The placebo effectThe word placebo is Latin for "I will

.please." A placebo is a pill or tabletwith real-looking numbers andmarkings but no active ingredients."A placebo is really just starch andfiller," says pharmacist PerryMackrill, of the University of Mary­land School of Pharmacy. "It hasno therapeutic effect, but it looksjust like real medication."

Although placebos contain noactive ingredient, they can stillhave an effect on the body. If aperson believes he is taking adrug, he may feel the side-effectsexpected from a real drug. Peoplewho have taken placebos havereported such symptoms as sleep­lessness, dizziness, nausea,blurred vision, even hallucinations.The placebo effect can be "quitepowerful," says Dr. Howard Spiro,author of Doctors, Patients, andPlacebos. Some experts say thatup to half of the success of realdrugs is due to the placebo effect.

10 CHEM MAnERS, DECEMBER 1991

taneously and given the method thecredit," says Dr. Barrett. "The patientgets confused, and that may makehim more vulnerable when a seriousmedical condition develops. The nexttime, he may try homeopathy again,and delay appropriate medical careuntil it's too late."

Bruce Goldfarb is a Baltimore writer whospecializes in science and medicine. Hewrote "The Smell of Danger, "ChernMatters, Oct. 1988.

ReferencesBarrett, S. Health Scams, Schemes and

Frauds; Consumer Reports Books: NewYork,1990.

Cummings, S.; Ullman, D. Everybody's Guideto Homeopathic Medicines; Jeremy P.Tarcher, Inc.: Los Angeles, CA, 1990.

"Homeopathic Remedies"; Consumer Reports1987, Jan., 60432.

"Riding the Coattails of the HomeopathyRevival"; FDA Consumer 1985, March.

Spiro, H. Doctors, Patients, and Placebos; YaleUniversity Press: New Haven, CT, 1986.

Ullman, D. Homeopathy: Medicine for the 21stCentury; North Atlantic Books: Berkeley,CA,1988.

P.tientsfeel belter, they say,because a doctor has done some­thing "for their problem.

Medical researchers use place­bos when they are testing a newdrug. People who are in the experi­mental group receive the real drug,while the control group receives anidentical~looking placebo. In asingle-blind study, the patientsdon't know whether they are get­ting the real drug or the placebo.However, •experience has shownthat the doctormay unintentionallygive the patient clues-perhaps byfacial expreSSion or tone of voice­that.wouldsl,lggest whether a pill isreal.orplcicebo,

Mostr$Searchersnow.conduct"double-blind" studies, in whichsomeoneelsepack~gesand

codes thef)ills.~Ptl1.tneitherthepatient nor the doctOr knows whois takiJ:lgwhich. When the stUdy iscompleted, another researcherbreaks the cooe and analyzes thedata.

Serial dilutionMany chemical reagents areshipped and stored in concentratedform, then diluted for use-likeorange juice. For example, NaOH isoften used in the laboratory at aconcentration of 0.001 molar (M),but it is sold and shipped as a 6-Mstock solution-6,OOO timesstronger. If you needed a beaker ofthe dilute NaOH you could measurea very small sample of the concen­trated NaOH and dilute it with avery large volume of water. "But theuncertainty in measuring a very tinyamount is astronomical. An error ofone drop can count a lot," saysTowson State University chemistryprofessor Joseph Topping. "Youmay end up with a solution that'sdilute, but not very close to whatyou were shooting for."

Serial dilution is a more accurateway to get a precise concentration."You take 10 mL of the stock solu­tion and dilute with water to make aliter. Take 10 mL of that solution,and dilute it to get another liter ofweaker solution," Topping explains."By doing the dilution in a numberof stages, the margin of error isminimal."

Homeopathic medications areprepared by serial dilution taken toan extreme. Consider how arnica-­a popular homeopathic remedy forsprains and other minor muscu­loskeletal injuries-is prepared.First, the flower and root of arnicamontana, the mountain daisy, arepicked. At a homeopathic drugcompany, such as Borion-Borne­mann in Philadelphia, PA, the plantmaterial is pulverized and soaked ina solution of water and alcohol forat least three weeks. "In time, allthe water-soluble and alcohol­soluble substances in that materialare extracted," says Mark Land, ofBorion-Bornemann. The brownishtea-like liquid that results is filteredand tested. Next, a small sample ofthe liquid is diluted in a ratio of 1:10or 1:100 with water or alcohol. Thedilution is repeated at least 5 andsometimes 12, 24, or 100 moretimes.

10 mL1.0 M

6.02 x 1021 molecules

pharmacist continued the series.Examine the entry for a 12C dilu­

tion. Note that the number ofmolecules remaining is approxi­mately one (0.602 rounded to thenearest whole number). This indi­cates that each liter of the prepara­tion contains just one molecule ofthe drug. At 15C, there is approxi­mately one millionth of a moleculeremaining in the beaker. But,because molecules don't split intofractions when a solution is diluted,this means that you would have tobuy about one million liters of thispreparation to get one molecule.But most homeopathic medicinesare diluted far more than this, to30C or 100C. It is apparent, there-

B

Number of molecules(per liter)

fore, that almost all doses of theseremedies contain just water or alco­hol, without a single molecule of theoriginal drug.

How can a preparation workwhen it contains no drug? "We don'tknow why the product continues towork past the Avogadro number,"says Land. "We can't explain why itworks, but it does." Most doctorssay that the drug can't work underthese conditions, but perhaps thetreatment can. See the box "ThePlacebo Effect" for their reasoning.

6.0 x 1023

6.0 x 1021

6.0x1019

6.0x1013

6.0 x 103 = 60206.0 x 10-1 = 0.602

6.0 x 10-7 =0.000000602

1.0

0.01

0.00011.0x10-10

1.0 x 10-20

1.0 x 10-24

1.0 x 10-30

Concentration(M)

none

1C

2C

5C

10C

12C

15C

DilutionBetween dilutions, the liquid is

shaken 150 times by a ritualizedmethod. Dr. Samuel Hahnemann,founder of homeopathy, recom­mended that the solution be pound­ed against a resilient surface, suchas a leather-bound book. Somehomeopaths still follow this practice,but at Borion-Bornemann amachine is used.

Homeopathic drugs are labeledaccording to their serial dilutions,with X representing a 1:10 dilutionand C representing a 1:100 dilution.In Europe, remedies are commonlygiven in 30C strength, meaning thedrug was diluted 1:10030 times. Inthe United States, according toLand, remedies are given up to100,000C.

Let's examine a 1C dilution indetail. Suppose that a pharmacistplaces one mole of a powdereddrug in a large beaker, then dis­solves it in water to make 1.0 L ofsolution; call it Solution A. In thelanguage of chemistry, Solution Ahas a concentration of 1.0 M andthe beaker contains 6.0 x 1023

molecules of the drug. We'll regardthis as our starting "full-strength"solution. Next, the pharmacist pourssome of Solution A into a graduatedcylinder to get 10 mL (see figure),then pours this amount into anotherbeaker and dilutes it with water tomake 1.0 L of a more dilute solu­tion, Solution B. During the laststep, the volume of the solution wasincreased from 10 mL to 1.0 L, a1:100 or 1C dilution. Solution B has1/100 the original concentration (itis now 0.01 M), and the beaker con­tains 1/100 the original number ofmolecules (it now has 6.0 x 1021

molecules).If the pharmacist repeated this

process to get a 2C dilution, thesolution in the next beaker wouldhave a concentration of 0.0001 M(1/100 of 1/100 of the original con­centration) and there would be 6.0x 1019 molecules in that beaker.Note that the number of moleculesis reduced by two exponents (deci­mal places) with each C dilution.Here's what would happen if the

CHEM MATTERS, DECEMBER 1991 11

Stolen CameraBy Raymond S. Voorhees

A few days after I had given a talk on careersin forensic science at a local high school'sCareer Day, I received a call from the princi­pal of the school. Could I, he asked, helpthem investigate the theft of some cameraequipment?

A few weeks before Thanksgiving, somemembers of the school camera club hadpooled their own money and made a ratherlarge group purchase of photographicequipment, including camera bodies, lens­es, ~nd flash equipment. The equipmentarrived but, less than a week later, some­one broke into the club's storage closetand stole most of it.

At the homecoming football game oneof the girls who belonged to the club sawa student-not a member of the photoclub-taking pictures of the game with anew camera and telephoto lens thatlooked like the stolen equipment. Shewatched the young man take the cam­era to his hall locker and, while he hadthe locker door open, she saw whatappeared to be other camera equip­ment inside.

Armed with this information, theclub sponsor asked for and receivedpermission to have the lockeropened. The equipment inside wasthe same type as the stolen equip­ment, but were they the same items?Because the club had bought manyduplicate items, some pieces ofequipment could be identified onlyby their serial numbers. The clubsponsor had kept the shipper'smanifest, which listed the serialnumbers, but when he tried tomatch them he found that the seri­al numbers had been filed off ofthe equipment in the locker.That's when the principalcalled me.

Invisible numbersMy first step was to determinewhere the serial number shouldhave been on each piece ofequipment. If that location on

12 CHEM MATTERS, DECEMBER 1991

.

•

/....,-------..,.---------.

~II

Cross

tX[CI'JY

neutralized with a base, rinsedagain, and the number is pho­tographed. If the thief filed deeplyinto the zone of strained metal, oradded new strains, restorationmay be impossible.

Die----o~-

y

·,.\if'.......•;.

Topview ID~--r----t....X r

clay and filled with reagent. Some­times the dissolution is accelerat­ed by using a 6-volt battery toapply a weak electric current.

As soon as the serial numberappears, E, the surface is rinsed,

Metal part withserial number

Straining for a solutionWhen a camera is manufactured,the serial number is stamped intothe metal with a hardened steeldie, which, like a rubber stamp,has backward-reading raised let­ters. See the illustration, part A.Forced into the metal under highpressure, the die squeezes themetal and disturbs its crystallinestructure, B. When the die isremoved, the metal directly belowthe stamped numbers has aninvisible but permanent strain(shown in color).

The thief typically removes theserial number by filing down themetal, stopping when the numbersare no longer visible, C. Underproper chemical conditions, theatoms of the strained regionundergo chemical oxidation fasterthan the normal metal. This meansthat a forensic chemist can care­fully dissolve the metal surfaceand watch the numbers reappearas the strained metal dissolvesfaster than the surrounding metal.

In the laboratory, the mutilatedsurface must be carefully polishedwith emery boards of increasinglyfine grain, D. This makes it easierto see any changes, and makes itmore likely that the entire numberwill emerge at once, instead ofone digit appearing, only to fadeas another digit appears.

When the metal to be analyzedis iron or steel, forensic chemistsuse a solution of copper (II) chlo­ride, made acidic with hydrochloricacid. The iron dissolves during anoxidation-reduction reaction withthe copper ions:

Cu2+(aq) + Fe(s) -0

Cu(s) + Fe2+(aq)

The etching reagent is oftenapplied with a cotton swab though,in some cases, a dam is construct­ed around the area with modeling

CHEM MATTERS, DECEMBER 1991 13

the equipment had been defaced,I photographed the damage. I alsomade, for reference, close-up pho­tographs of undamaged serialnumbers from the same type ofequipment. These would provevaluable for comparisons during therestoration process. Armed withthese photos and a copy of the ship­per's manifest with the serial num­bers, I went to work.

Carefully, I polished the mutilatedsurface to a mirror-bright finish. Thiswas to insure that I could detect eventhe slightest change in the metal'sappearance during the subsequentetching process. I then began to etchthese surfaces, one at a time, using aweak acid solution under the influenceof a low electric current. I stoppedoften to examine the surface and,when I saw some numbers appear,immediately applied a basic solution toneutralize the acid and bring the pro­cess to a halt.

Although I did not retrieve all of theobliterated numbers, I was able torestore the entire serial number fromthree camera bodies and a very expen­sive flash unit, as well as significant por-tions of the serial numbers from threelenses. However, I had no success at allwith another flash unit from a differentmanufacturer. The recovered numbers allmatched the serial numbers on the mani­fest of equipment that had been shipped tothe school. When the student was con­fronted with these results, he confessed tothe theft and was arrested.

Raymond S. Voorhees has degrees in adminis­tration of justice and forensic science. He worksas a firearms and too/mark examiner for the U.S.Posta/Inspection Service in Washington, DC.

ReferencesMassiah, E. E. "A Compilation of Techniques and

Chemical Formulas Used in the Restoration ofObliterated Markings"; Assoc. Firearm Tool MarkExaminers Journal 1976, 8, 26.

Polk, D. E.; Giessen, B. C. "Metallurgical Aspects of theSerial Number Recovery"; Assoc. Firearm Tool MarkExaminers Journal 1975, 7, 38.

Thornton, J. I.; Cashman, P. J. "The Mechanism of theRestoration of Obliterated Serial Numbers by AcidEtching"; J. Forensic Sci. Soc. 1976, 16,69.

A recent study of the mint plant Dicerandra frutescens revealed that its leavescontain microscopic capsules filled with insect-repelling oil. In this experiment,ants-which had been feeding on a O.1-M sugar solution-flee when a freshlybroken leaf is held nearby. D. frutescenswas discovered only in 1962, but is nowlisted as an endangered species.

IAT

Roger Segelken is a science writer forCornell News, Cornell University, Ithaca,NY.

ReferenceChemoecology1990, February, 30-37.

gy, where they attracted the interestof several major chemical manufac­turers.

It's too soon to say whether trans­pulegol will ever be available com­mercially, but two important factorsrecommend the new repellent.Because it is easily synthesized,large quantities could be made with­out harvesting the rare mint plant.Also, because it is a natural material,it is less likely to prove harmful to theenvironment than repellents inventedsolely in the lab.

Dicerandra frutescens is an endan­gered species and survives in only afew patches in central Florida. "Wecould wipe out all the Dicerandrafrutescens in the world in a few hourswith a lawn mower-or a few minuteswith a bulldozer," says Mark Deyrup,one of the scientists who collaboratedin the study. The discovery of thisnatural repellent illustrates the urgentneed to identify useful chemicals inplants, insects, and other life formsbefore more species disappear.

CliFT

graduate student Kevin McCormick,who analyzed the contents of thecapSUles and found a mixture ofoils-a dozen well-known mint oilsand one new one. A thorough chemi­cal analysis identified the unknown oilas trans-pulegol. The chemists thensynthesized trans-pulegol (that is,made some in the laboratory fromsimple compounds) to confirm thechemical identity of the previouslyunknown repellent. The results werepublished in the journal Chemoecolo-

Chemical analysis showed that the oilin Dicerandra frutescens contains 12insect-repelling compounds. Theprimary component is trans-pulegol,above, a compound that waspreviously unknown to chemists.

By Roger Segelken

Thomas Eisner was walking throughthe pine scrub of central Florida whenhe brushed against a short plant. Theair was soon filled with an intensepeppermint-like scent. Eisner, a biolo­gist at Cornell University in Ithaca,New York, noted that the plant wasDicerandra frutescens, a rare mem­ber of the mint family. Closer exami­nation revealed that the leaves were"remarkably free of insect-inflictedinjury," says Eisner. Those twoclues-a strong odor emitted onlywhen a leaf was damaged, and thelack of insect injury-led him to aseries of revealing experiments.

Eisner took some leaves to thelaboratory of the Archbold BiologicalStation in Lake Placid, Florida, to testtheir effect on insects. When anundamaged mint leaf was offered to acircle of ants feeding on a sugar solu­tion, the ants took no notice. Butwhen the leaf was cut, to simulateinjury from an insect bite, the aromamade the ants stop feeding and flee.Next, using a standard test for chemi­cal irritants, Eisner dabbed leaf mate­rial on the abdomen of a cockroach.The cockroach immediately beganscratching itself. Unquestionably, theinsects disliked something in the leaf.

Why was there no effect before theleaf was damaged? Eisner traced thescent to an oily liquid contained inmicroscopic capsules within the leaf.The oil is not released until the leaf isdamaged by an insect. "We weren'tsurprised to find chemical defensesencapsulated in the leaves; manyplants have that defense," Eisnersaid. "However, these capsules arehermetically sealed to prevent evapo­ration of the volatile oils until the cap­sules are punctured. That feature is away of reducing the plant's 'defensebudget.' It's probably a general phe­nomenon that we biologists haveoverlooked."

Eisner enlisted the assistance ofCornell chemist Jerrold Meinwald and

CHEM MATTERS, DECEMBER 1991 15

25. What I do is none of your __ ,!26. What the police do to drug par­

ties.27. How we refer to the guy who had

his stomach removed.28. What the Lone Ranger did to his

horse.

Answers: Ag Au B Ba Bi CmCu Eu Fe He Hg Ho N NiNo Pb Ra Rh Si atom, catalyst,chemical bond, chromates, elec­trolyte, nitrates, oxides, polygon, sili­cate, waterFor solutions see page 3.

17. The outside of oxen.18. The 007 of the chem lab.19. Twice a half-nium.20. Eve's husband. ~

21. Prisoner who sniffed laughinggas.

22. Soldier from Troy who only fightsafter dark.

23. What a doctor should do for hispatients (two answers).

24. Greek streaker who wore shoeswith wings.

Riddled with PunsBy Ned GaultLeigh High School, San Jose, CA

The statements below are punny rid­dles. Pick the correct answers fromthe list at the bottom of the page.Each answer is either one of thechemical terms listed or the name ofone of the elements listed. For exam­ple, the answer to 1 is Cu (copper).

1. Person who gives admissiontickets to traffic court.

2. Half a dime.3. What they do with dead people.4.. What all that glitters is not.5. Cheaper than day rates.6. Man who raises cows in Texas.7. Goofy Aunt Katherine.8. Dead parrot.

POZZLE PACJE

9. What you do to cattle that getaway.

10. What a horse has to be if hewon't go for water.

11. Lone Ranger's horse.12. When it's dark, you turn it on and

it gets light.13. A really "pressing" thing.14. What most lectures are.15. HIJLKMNO16. Mr. & Mrs. Crow.

16 CHEM MATTERS, DECEMBER 1991