Question From the Classroom
By Bob Becker
Q. Do scientists always follow “the scientific
A.
That depends on what
you mean by the scientific
method. If you’re talking about
dreaming up a hypothesis,
and then writing out a list of
materials, followed by a
method section involving 10
steps, the answer is pretty
simple: Not a chance!
Take early flight experiments, for example. What two
courageous brothers, through
sheer determination and guts,
were responsible for ushering
in the age of air travel? Easy,
huh? Well, if you’re thinking of
the Wright Brothers, you’ve
got the wrong brothers! In
fact, you’ve got the wrong
continent and the wrong century! We’re talking about the
Montgolfier brothers, Joseph
and Etienne, in France back in
1783, who designed and flew
the very first manned aircraft—a hot air balloon.
Today, we honor them as scientists in the finest sense of
the word!
Their first “balons” were
simply lightweight bags made
of silky linen and paper. Held
over a fire, they inflated;
released, they ascended as
high as 180 meters (m). The
brothers first caught the public eye by launching their 663cubic-meter (23,400-cubicfoot) balloon from the marketplace in Annonay, France. It
turned out to be a real crowd
pleaser, climbing to a height
of over 1.8 km before cooling
down and descending to the
2 ChemMatters, APRIL 2002
ground about 25 km away.
So it worked according to
plan every time. Right? Not
quite. The Montgolfier brothers, as well as other early balloonists, had no list of steps
to follow. There were many trials, and there were some
memorable errors along the
way.
Here are a few of the early
balloon “experiments”. This is
science? You be the judge!
• Thinking that it was the
dense, choking smoke that
caused the balloons to lift,
the brothers insisted on
burning only the smokiest
and stinkiest materials they
could find—wet straw,
chopped wool, and for one
special demonstration in
Versailles, old shoes and
rotten meat! The King and
Queen were invited to
examine their amazing
machine, but the unbearable stench drove them
away! Later, the brothers
realized it was just the hot
air, not the smoke or stench
quality, that caused the lift.
• Three months after their
first balloon launch, the
Montgolfier brothers built
an even larger balloon, this
time to determine if airborne passengers—a
sheep, a duck, and a rooster—would survive the trip.
The three pioneers returned
safely, the only injury being
a broken wing on the rooster. The sheep got excited
•
•
messages sent
back and forth
in a bag attached
to a long cable. It
worked. The
French won the
battle in part
because the plan
helped the French
direct their artillery
fire. But more important, they won because the
balloons convinced the
Austrians that the French
must be in alliance with the
devil.
Before long, aeronauts were
becoming astronauts. In
1804, French Chemist
Joseph Gay-Lussac and his
brother made an ascent in a
hydrogen balloon to
research the atmospheric
composition and the Earth’s
magnetic field. Even though
Joseph passed out from a
lack of oxygen, they
reached an altitude of
7000 m, a record that
remained unbroken for
nearly half a century.
ENGRAVING OF AN EARLY MONTGOLFIER BALLOON COURTESY OF ALLSTAR: WWW.ALLSTAR.FIU.EDU
method” when they do experiments?
and inadvertently
stepped on him.
At pretty much the same
time, the French physicist
Jacques Charles (as in
Charles’s law) was experimenting with hydrogen•
filled balloons. Because
hydrogen was considerably
less dense, the balloons
could be much smaller. And
because they did not need
fuel, they could stay aloft
for longer periods of time.
The first of these was an
unmanned balloon launched
from the Champ de Mars. It
rose to 900 m and landed
25 km away in a remote
farmland. Terrified villagers
attacked and “killed” the
descending monster with
clubs and pitchforks!
And there were military
contracts! In 1794, in
the Battle of Fleurs,
the French used
tethered balloons to
observe
FIND YOUR COMPLETE
movements
TEACHER’S GUIDE FOR THIS ISSUE AT
of the
www.chemistry.org/education/chemmatters.html.
enemy
Austrian
troops with
M
C
TEACHERS!
®
Vol. 20, No. 2
DEPARTMENTS
Question From the Classroom
APRIL 2002
2
Do scientists always follow “the scientific
method” when they do experiments?
The pioneers of flight did a lot of trials and made even more
errors, but we’ll let you decide about the method they followed—
scientific or otherwise.
PHOTO SOURCE: SCIENCE IN A TECHINICAL WORLD, © ACS
10
ChemSumer
Hair Color: Chemistry To Dye For
GE
TT
Y
BY
PH
OT
O
MysteryMatters
IM
AG
ES
Whether you’re thinking about a few highlights or a whole new
color “do”, here are the chemistry details behind the stuff that
does the job.
12
Forensics: Finding the Chemical Clues
Even the faintest chemical traces at the crime scene can hold the
keys for finding “whodunit”.
Chem.matters.links
16
Browse through these links for cave explorations, balloon
launches, hair dye facts, FBI routines, and even a site for your
chemistry exam review.
CM Puzzler
What’s the difference
between a stalactite and
a stalagmite? Find the
answer in this issue of
ChemMatters!
FEATURES
4
Hot Air Balloons: Gas and Go
For floating with the breeze, you need a source of hot air, a little
courage, and a few gas laws. We’ll show you how to make and
launch your own balloon.
Caves: Chemistry Goes Underground
7
When the pH is right, even solid rock can dissolve to open up
beautiful and sometimes dangerous underground caverns.
Chemical Profiling—
Tracking Down the Source
14
Tracing illegal imports to the source is the job of a group of
analytical chemists. They’re finding that everything from drugs to
orange juice carries the signature of its home base.
COVER PHOTO BY GETTY IMAGES
Production Team
Helen Herlocker, Managing Editor
Cornithia Harris, Art Director
Leona Kanaskie, Copy Editor
Administrative Team
Michael Tinnesand, Editor
Julie Farrar, Creative Director
Elizabeth Wood, Manager,
Copy Editing Services
Guy Belleman, Staff Associate
Sandra Barlow, Program Assistant
Technical Review Team
Seth Brown, University of
Notre Dame, IN
Frank Cardulla, Northbrook, IL
Teacher’s Guide
Frank Cardulla, Editor
David Olney, Puzzle Contributor
Division of Education and
International Activities
Sylvia Ware, Director
Janet Boese, Assistant Director for
Academic Programs
Policy Board
Susan Cooper, Chair, LaBelle
High School, LaBelle, FL
Lois Fruen, The Breck School,
Minneapolis, MN
Al DeGennaro, Westminster High
School, Westminster, MD
Doris Kimbrough, University of
Colorado-Denver
Ronald Perkins, Educational
Innovations, Inc., Norwalk CT
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ChemMatters, APRIL 2002 3
Hot Air
BalloonS
GAS AND GO
By Claudia Vanderborght
The tires hum a deeper song as we slow down;
then they crunch on gravel as we make the turn.
The headlights bounce, slicing a path through the
darkness. Already, the stars are fading as daylight
approaches. The ground crew waits for us in the
recently plowed field. As we join them, the aroma
of coffee and fresh doughnuts overwhelms the
dewy, earthy smell of the early spring morning.
E
veryone gets busy unpacking the large gasoline-powered
fan, lifting the wicker basket from the pickup bed, and
unrolling the hundreds of meters of nylon. The pilot
releases a small helium balloon and studies the air currents that
whisk it away. With a noisy growl, the fan starts up. The yellow
and blue panels lift off the ground and undulate. In the predawn
light, the inflating balloon looks like some weirdly colored monster slowly rising out of the earth.
Into a sky streaked with red and orange, the sun bursts over
the distant mountains. The propane burner blasts its noise and heat
into the morning. As the air inside the balloon warms, the balloon
expands, and the nylon envelope is pulled from the ground.
The wicker creaks as we climb into the basket. Within minutes, the balloon towers over us, tugging at the ropes that fetter it
to the earth. At the pilot’s signal, the ground crew loosens the
ropes and the balloon pops into the air. We wave to the crew,
already occupied with packing up gear and loading it into the vehicles that will follow us.
Up and away
Early balloonists discover the
gas laws
Many of our gas laws were discovered by balloonists. The
Montgolfier brothers came up with the idea of launching and testing hot air balloons after observing that smoke never flowed down
a chimney. Jacques Charles, a French physicist, knew that the
4 ChemMatters, APRIL 2002
www.chemistry.org/education/chemmatters.html
PHOTO FROM GETTY IMAGES
As air inside the balloon heats up, the molecules move faster
and faster. If the balloon were sealed, pressure would soon build
to the bursting point. But molecules are free to escape. Before
long, the hot air inside the balloon is less dense than the cool air
that surrounds it. Just as an object less dense than water rises to
the surface, our balloon filled with hot air rises through the surrounding air. And we are off!
Gaston, our pilot, checks two gauges—the variometer measures the balloon’s rate of ascent or descent. We’ve been climbing
steadily for the past five minutes. The altimeter indicates our distance from the ground. We’re 350 meters above the ground—a
nice cruising height—so Gaston shuts off the propane burner.
It is amazingly quiet up here! Montgolfières (the French term
for hot air balloons) are propelled by the wind. But we are only
aware of floating. In a balloon you neither feel nor hear the wind,
since you are traveling with it. That is why a ground crew is essential. You never quite know where you’re going to end up because
the wind, not the pilot, determines the flight path.
PHOTOS COURTESY OF THE LOWELL SCHOOL, WASHINGTON, DC
is much colder at higher altitudes. As a
general rule, the temperature drops 10 °C
for every kilometer of ascent.
Sunlight dances on the hills below
us, adorned with the lacy greens of spring
foliage. We’ve been aloft for nearly an
hour when Gaston radios the ground crew
to discuss suitable landing sites. Ballooning is safest during dawn or dusk. Our
morning air is becoming bumpy with turbulence. Warmed by the sun, the air rising from the hills reaches us sooner than
the air from the valleys. As a result, we
lose altitude in the less dense warm air,
but we are quickly buoyed up as we drift
over the valley. It’s fun, but our thermal
roller coaster ride can become dangerous
if the pilot loses control over the balloon.
Different materials heat up at different rates. Air over a recently plowed field
will heat up and cool down faster than air
over a lake. As the sun climbs higher and
shines directly down on the earth, these
thermal contrasts become more intense.
In preparation for landing, Gaston
pulls the cord to the vent. Hot air at the
balloon’s apex escapes, cool air rushes
into the appendix to replace it. We slowly
descend as our balloon becomes filled
with denser air. Finally, gravity wins.
Landings can be a little rough, but
Gaston is an experienced pilot. Just
before we land, he pulls the rip cord,
which opens the top of the balloon and
deflates it behind us. The wicker basket
flexes and creaks as we touch ground,
Students at the Lowell School in Washington, DC, make
absorbing
most of the landing energy, so
careful measurements as they construct their balloons.
that the passengers are barely upset. The
ground crew rushes up with smiles, paper
cups, and a bottle of champagne. It’s the tradimeters of nylon. Deflated, it weighs 85 kilotional French way to celebrate a successful
grams (about 190 pounds). Inflated, however,
balloon flight.
our balloon displaces nearly three tons of air!
CLIP ART FROM ACS FILES
newly identified hydrogen gas would lift
balloons far better than hot air. His first
experiment, launched from Paris, was
supremely successful! The unmanned balloon shot a mile into the sky and eventually landed 25 km away, terrifying the
peasants, who hacked at the flying “monster” with pitchforks until it no longer
“breathed”.
Charles’ law—the volume of a gas
will increase as its temperature increases,
when kept at a constant pressure—is
named after its discoverer. Professor
Charles applied his discovery to making
improvements to the airships. Early flights
were brief because the balloons quickly
deflated. The buoyant gases escaped
through the silk fabric’s weave. Charles
coated the silk with rubber dissolved in
turpentine, sustaining flights by slowing
the diffusion of hydrogen or hot air from
the balloon. He suggested adding a vent
to the top of the balloon. The vent allows
pilots to release gas from the apex, thus
giving them control over the descent.
Early balloons had an alarming tendency to explode. Pilots, hoping to set
new altitude records, heated the flammable hydrogen to decrease its density. Not
surprisingly, some met their deaths in
spectacular, fiery crashes. Sometimes
the inexperienced balloonist failed to balance the amount of air inside the envelope with the rate at which it was heated.
The rapid ascent to high altitudes
The flight ceiling
strained the silk beyond the tolerance limit.
The balloon burst, plunging the occupants to
their untimely deaths.
Our balloonist Gaston fires the burner
again, reheating the air to regain our lost altitude. It’s good to know that skirts of contemporary balloons are treated with a flame
retardant. The average sporting balloon stands
about seven stories tall and, depending on its
design, is made from about 1000 square
As the density of the balloon approaches
the density of the surrounding air, our ascent levels off. We’ve reached our flight ceiling at 1500
meters (or about 5000 feet) above sea level.
Many balloons attain even greater altitudes, but flying conditions deteriorate and
danger increases. The air pressure at 3000
meters is barely 70% of the pressure at sea
level. As the total pressure decreases, the partial pressure of oxygen also decreases—making it more difficult to ignite the propane.
Or to breathe! Many early balloonists lost
their lives by suffocation as they tried to set
higher altitude records. The lucky ones only
lost their fingers and toes to frostbite, since air
Claudia Vanderborght is a high school chemistry
teacher and science writer in Swanton, VT. Her
recent article “Maple Syrup: Sweet Sap Boils Down
to This” appeared in the February 2002 issue of
ChemMatters.
REFERENCES
Bloomfield, L. A. How Things Work—The
Physics of Everyday Life; Wiley & Sons:
New York; Chapter 3.1.
Flynn, M. The Great Airships; Carleton Books
Ltd.: London, 1999.
Norwood, A. Taming the Gentle Giant: A
Guide to Hot Air Ballooning; Taylor
Publishing Co.: Dallas, TX, 1986.
Schaefer, V. J.; Day, J. A. A Field Guide to
the Atmosphere; Houghton Mifflin Co.:
Boston, 1981.
ChemMatters, APRIL 2002 5
ILLUSTRATION FROM ACS GRAPHICS CLIPART FILE
ACTIVITY:
Try it! Make Your Own
Hot Air Balloon
Make your own hot air balloons and launch them from your
school grounds. Although there is probably little risk of terrifying
the local “peasants” with your “monsters”, it’s a good idea to
get clearance from local authorities before you launch.
Build it
1. Prepare a total of 8 panels of tissue paper by
Assemble materials
gluing together three separate sheets as shown in (a).
24 sheets of tissue paper,
various colors
2.
Scissors
(a)
Glue
(b)
80 cm
Masking tape
Thermometer
80 cm
Hole for
thermometer
in one of
the gores.
50 cm
String and/or streamers cut
from tissue paper
Small camp stove with fuel
60 cm
Short section of stovepipe
Short ladder for standing while
you read the thermometer
Next, stack the
panels and staple
them together at
the corners. Trim the
stack of panels to make
8 "gores" with the
dimensions shown
in (b).
50 cm
60 cm
75 cm
75 cm
Heatproof mits for handling the
hot stovepipe
Fire extinguisher
17 cm
cm
17
Balance suitable for weighing
the balloon assembly
3.
Determine the mass of
your balloon assembly
Do this if you are going to do the calculations your teacher may assign at the
end of the activity. After the glue dries,
gently fold the balloon. Either weigh it
directly, or weigh it enclosed in a tared
container.
Check for safety
Do this activity outdoors on a nonwindy
day, away from flammable materials.
These directions are for supervised
classes only. Have a fire extinguisher
on site, and review instructions for
using it. Wear heatproof mits when
handling the hot stovepipe.
readings are important for doing the
calculations your teacher may assign.
Punch a small hole in the top section
of the balloon, just big enough to lower
a thermometer suspended on a string
Ignite a small camp stove, and surround it with a few upended bricks.
Place your stovepipe section over the
camp stove. Position the bottom of the
balloon over the stovepipe, and hold
the balloon while it inflates with the
warm air.
Try to adjust the heat to the point
where the balloon just “hovers”, neither
rising nor falling. Note this temperature. Then, increase the temperature a
few more degrees, remove the ther,
mometer, stand back, and let er go!
Think about it
Launch it
Record the outside air temperature
at time of launch. These temperature
6 ChemMatters, APRIL 2002
Separate the gores. Glue each edge to a neighboring gore to form the balloon.
Reinforce the open bottom edge with masking tape, and attach several evenly
spaced streamers and/or pieces of string to the bottom. These should increase
the stability of your balloon.
Assuming your balloon survives
intact, try launching again with either a
lower or higher initial launch tempera-
www.chemistry.org/education/chemmatters.html
ture. What’s the effect of the temperature change on altitude?
Your balloon rises because it is an
object at lower density than the air
around it. Suppose you had “molecular
snapshots” of the way air molecules
were arranged inside and outside the
balloon. How would they compare?
Send pictures!
By all means, let ChemMatters help you
celebrate your success. Send pictures
and some notes about your launch to
ChemMatters, American Chemical
Society, 1155 16th St., NW, Washington, DC 20036. Or you can send in digital format to [email protected].
We’ll post them on the Web at www.
chemistry.org/education/
chemmatters.html.
Y
ou might think caves are only interesting to rock-collecting
geologists. Think again. There’s a lot of chemistry going on in
a limestone cave. But don’t expect any fireworks. Cave chemistry goes veeeery sloooowly.
Bazillions of years ago—well, more like 300 million years ago—
oceans covered much of the earth. Many animals in the oceans had
shells and exoskeletons made of calcium carbonate (CaCO3). As these
creatures died, their calcium carbonate sank to the ocean floor. Gradually, very gradually, geological processes known as sedimentation (settling) and lithification (solidifying) turned these deposits into carbonate
rock. The most common form of carbonate rock is limestone.
Limestone is made up mostly of calcite, a particular structural form
of calcium carbonate. There are often other minerals mixed in—mostly
magnesium, but also iron, zinc, sodium, potassium, silicon, and more.
But calcium carbonate makes up more than 95% of limestone.
We think of rocks as solid, immovable things, thus, the expression,
“solid as a rock”. In fact, some rocks, like limestone, are particularly susceptible to different types of erosion. The erosion that results in the formation of caves is a dissolution process. Dissolution means that the rock
is literally dissolving away.
The secret of caves we unlock:
If limestone’s the same
thing as chalk,
Then water flows through
And dissolves CO2
Making acid that eats
through the rock.
By Doris R. Kimbrough
Limestone, the rock that
dissolves
Calcium carbonate is not particularly soluble in plain water. Stick a
piece of chalk in a glass of tap water, and it will get mushy as it absorbs
water, but only a tiny amount will actually dissolve. Chemists sometimes
show an “unfavored” reaction like this with a very small arrow:
CaCO3(s) ➞ Ca2+(aq) + CO32–(aq)
So how on earth can enough rock dissolve away to form something
as vast as the Carlsbad Caverns of New Mexico? Suppose you put that
same piece of chalk in some vinegar, which is acidic. Now the chemistry
gets going. Try it! The calcium carbonate readily dissolves, as the larger
reaction arrow indicates.
CaCO3(s)
Ca2+(aq) + CO32–(aq)
The calcium carbonate doesn’t just dissolve, it dissociates, meaning
that it separates into its independent ions. How does acid cause this to
happen? There is actually a second reaction going on at the same time—
one that involves the carbonate ion (CO32–).
CO32–(aq) + H+(aq) ➞ HCO3–(aq)
➞
www.chemistry.org/education/chemmatters.html
ChemMatters, APRIL 2002 7
And it’s this second reaction that favors
the dissolving of the calcium carbonate. If
you’ve learned about chemical equilibria, you’ll
recognize this as a series of equilibria—one
favored, one not.
CaCO3(s) ➞ Ca2+(aq) + CO32–(aq) NOT favored
Water carves out
caves—drop by drop
As rainwater becomes groundwater, it
seeps into the cracks and joints of underlying
bedrock. If that bedrock happens to be limeSo the net process is
stone, as it is in many parts of the world, the
–
+
2+
CaCO3(s) + H (aq) ➞ Ca (aq) + HCO3 (aq)
acidic water soon dissolves the rock. Small
cracks become channels; channels become
which we get by just adding the two equilibcaves.
rium equations together.
The fact that the water is flowing is
OK. We’re talking about caves, not chemimportant
for cave formation. Earlier, we menistry labs. Where does the acid come from? It
tioned
equilibrium.
Cave making takes place
comes from the soil. Dirt?
when
the
acidic
water
and the dissolving calFirst let’s see what carbon dioxide has to
cium
carbonate
never
reach
equilibrium.
do with acid. Carbon dioxide is soluble in
Because
the
water
is
flowing
through the rock
water. Most of it simply dissolves, but some of
rather
than
just
sitting
on
top
of it, new calit actually reacts with the water to form carcium
carbonate
is
constantly
being
exposed to
bonic acid (See “The Fizz-Keeper” in the Februfresh
supplies
of
acidic
water.
ary 2002 issue of ChemMatters). And when
It works like this. If you put a carbonate
this carbonic acid ionizes, hydrogen ions are
rock
in
a beaker of aqueous acid, some of the
produced. That’s why we call it an acid.
–
+
H2O(l) + CO2(aq) ➞ H2CO3(aq) ➞ H (aq) + HCO3 (aq) rock dissolves, but eventually the
process reaches equilibrium. At that
water carbon dioxide carbonic acid
point,
as
much calcium carbonate would be
Carbonic acid is what makes seltzer and
dissolving
as would be precipitating out.
sodas acidic. So if there is excess carbon dioxIt’s
like
a roller coaster ride in an amuseide around, it will dissolve in water and lower
ment
park.
Think
of the people riding the roller
the pH. Calcium carbonate’s (i.e., limestone’s)
coaster
as
the
dissolved
calcium carbonate.
solubility is very sensitive to pH. If you look at
As
soon
as
the
train
is
full,
no more people
the table below, you can see that very slight pH
can
get
on
until
others
get
off.
We can accomdifferences can make an enormous difference
modate
more
people
by
adding
a second train
in how much CaCO3 will dissolve.
(akin to lowering the pH a bit more), but ultiMaximum amount of CaCO3
mately the number of people (rock) we can
pH
that can dissolve (mg/L)
accommodate (dissolve) is limited by the fact
6.48
577.3
that we are at equilibrium.
6.92
316.2
Now suppose that instead of a roller
7.27
212.9
coaster
on a finite loop of track, we have a
8.27
52.2
conveyer belt that stretches off to infinity. As
soon as some people get on, they are moved
And it’s the soil that supplies all of this
on by the conveyer belt (flowing acidic water),
carbon dioxide. How does it get into the soil?
making room for new people to board this
From the air? Atmospheric CO2 is typically present in caves at concentrations around 0.03%
or so, but that’s not enough to dissolve a significant amount of limestone. Let’s go back a
few hundred million years. After the limestone
formed, it gradually became buried in layer
after layer of soil. Plants grew, plants got eaten
by animals, animals ate other animals, animals
and plants died—and bacteria went to work
recycling all of them. As the bacteria decomposed all of this organic matter, they produced
CO2 as a waste product. Since this CO2 formed
underground, little of it escaped into the
Drop by drop, rocks form. Drops from the ceiling
atmosphere. When water drained through the
form stalactites. Drops hitting the floor pile up to
form stalagmites.
soil, it dissolved the CO2 produced by the bac–
3 (aq)
8 ChemMatters, APRIL 2002
favored
PHOTOS: © PETER JONES, SITDCP, [email protected]
➞ HCO
Lechuguilla Cave within Carlsbad Caverns
National Park is the site of a variety of
speleothems. The popcorn and aragonite
formations (top) are found in an area called the
“Velvet Underground”. The cave pearls (bottom)
are from an underground lake location called the
“Pearlsian Gulf”.
PHOTO BY GETTY IMAGES
CO32–(aq) + H+(aq)
belt. The faster the belt moves, the faster it
can relocate (dissolve) the people (rock). As
long as we don’t run out of belt (acidic water),
we will never reach equilibrium.
Over time—hundreds of thousands of
years—surface waters progressively cut into
the rock mass. Gradually, soil erosion and
other geologic events like earthquakes, landslides, and volcanoes can leave upper underground streams relatively dry. A system of
caves may have dry upper hollowed out caverns at the same
time lower channels and chambers
are still forming. The drying
out of caves is
important for a
process called
“degassing”,
which leads to
the formation
of speleothems.
What?
Speleothems is
a collective
teria. Up went the H+ concentration; down
went the pH.
term that includes all the amazing rock formations that you see in caves. Of these, stalactites (down) and stalagmites (up) are probably
the most familiar, but the term also includes
the often beautiful flowstones, crystal formations, columns, shields, cave popcorn (globulites), spattermites, cave flowers (anthodites),
and cave pearls (concretions)—all of which
lure enthusiastic cavers to the scene.
The various forms taken by speleothems
result from the events that take place during
the degassing process. A water drop on the
cave ceiling hangs for a short time before
falling to the floor. As it hangs suspended, two
things can happen: Some of the CO2 dissolved
in the drop diffuses into the cave air because
Sinkholes
1994 appearance in
Maryland, suddenly
and catastrophically.
What caused
he April 1, 1994, issue of the Carroll County Times of rural
the overnight
Maryland carried a front-page story that was no April
appearance of the
Fool’s Day joke. Staff writer Jennifer Hill wrote the followsinkhole on Marying dramatic account:
land Route 31?
Callie Woodson and her son Andy drive on Maryland 31 from
James Reger of the
their New Windsor home to Westminster every morning before the
sun rises.
Maryland Geological
She’s seen potholes and she’s driven over bumps, but Callie
survey couldn’t be
had never seen anything like the giant crater she encountered in
sure, but he thought Sinkholes like this one that suddenly appeared in a
the roadway just after 2 a.m. Thursday.
southwest Florida community threaten lives and
that the unusually
Seventy feet wide and 15 feet deep, the sinkhole took up the
property.
wet month of March
entire westbound lane of the road near the intersection with Medford Road.
was a factor. He called rainwater “aggressive water”. As it seeps
“It just looked like it was black on the other side of the road,”
through soil, it becomes acidic, dissolving more rock than underWoodson said.
ground stream water. Reger theorized that the rainwater, together
Then they saw the van.
with the freezing and thawing of an unusually cold winter, caused a
“We could see a back wheel and fender sticking out. My son
sudden rush of water into a cave passage beneath the surface. No
called to the driver . . . , but no one answered.”
They flagged down another motorist who contacted the state police.
longer supported by groundwater pressure, the soil and rock under
the road collapsed.
Sinkholes can also be caused, at least in part, by the opening of
Rescue teams trained in cave-ins assisted local fire departcavities produced by groundwater extraction or mining. Was the
ments to free the victim. Fearful that the earth around the hole
limestone quarry a few miles from the Maryland site a factor in the
would give way any minute, rescuers tethered to ropes rappeled into
fatal crash? That possibilthe hole while others shined
ity is still being hotly conflashlights.
tested without resolution in
Tragically, despite their
the local press and in the
efforts, the rescued driver
courts.
died in the hospital hours
Besides caves and
later.
sinkholes, karst landforms
A cave is only one examinclude canyons, gorges,
ple of a karst formation. Karst
pits, karren (channels),
is a broad term that includes
towers, and the dramatic
all types of geologic formaarches and rock formations
tions that result from dissolvthat exist in Monument Valing rock. Sinkholes are
ley or Garden of the Gods.
another type of karst. SinkAlthough karst formations
holes form when rock disvary widely, they all share
solves underground in the
the same chemistry—the
same way described for
simple chemistry of a pHcaves, but the visible result is
dependent dissolution of
the sinking of the ground into
the widespread form of calthe cavity created by the discium carbonate called
solved limestone. They can
A variety of factors including lack of rainfall, lowered water levels, or, conversely,
excessive rainfall in a short period of time, can contribute to sinkhole development.
limestone.
form gradually or, as in the
PHOTO AND GRAPHIC: COURTESY OF THE SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
T
the cave air has low CO2 concentrations compared with the soil that the water just flowed
through. Second, if the cave has lower than
100% humidity—likely in caves open to the
outside—some of the water drop evaporates.
If one or both of these events take place, the
same thing happens. The dissolving equation
reverses as the solution becomes overloaded
with ions or supersaturated. Some of the dissolved CaCO3 precipitates back out.
Ca2+(aq) + CO32–(aq) ➞ CaCO3(s)
Speleothems can become impossibly
beautiful, particularly if colored by other dissolved minerals! A visit to the National
Speleological Society Web site at
www.caves.org links to some outstanding photographs to illustrate these underground wonders.
Doris R. Kimbrough teaches chemistry at the
University of Colorado–Denver. Her article “How
We Smell and Why We Stink” appeared in the
December 2001 issue of ChemMatters.
REFERENCES
Ford, D.C.; Williams, P. W. Karst
Geomorphology and Hydrology; Unwin
Hyman: London, 1989.
Gillieson, D. S. Caves: Processes,
Development, and Management; Blackwell
Publishers: Oxford, UK, 1996.
University of California at Berkeley, Museum
of Paleontology; www.ucmp.berkeley.edu
(accessed February 2002)
ChemMatters, APRIL 2002 9
ChemSumer
PHOTO FROM GETTY IMAGES
Hair Color:
Chemistry to
Dye For
WHAT’S THAT STUFF?
By Linda Raber
The article first appeared in Chemical & Engineering News,
March 13, 2000. It is reprinted with permission.
E
ver since Madonna became a megastar in the mid1980s, I—a natural brunette—had a not-so-secret
desire to be a blonde. Over the years, I made and canceled a few appointments to have my hair colored. I just
never had the nerve to go through with it until last summer,
when my gray streak had gotten so big it was no longer a
fashion statement. It was—well—gray hair!
So, I kept that last appointment. I was really going to
take the peroxide plunge. Sitting in the salon, my hairdresser
took what looked like a pastry brush and saturated my hair
with clear whitish goo that looked like icing for cinnamon
buns and told me, “There’s no turning back, now.” When I
10 ChemMatters, APRIL 2002
It’s prom time, and you’re getting all of the details, whether you
want them or not, over lunch table
strategy sessions that never seem
to quit. After the basics, the who
and where stuff, comes the real
core of the matter—looking good!
And somewhere down the line,
you start to wonder. Would I look
better as a blonde? A brunette?
Maybe a little lightening here and
there? Permanent? Temporary?
Should I? Decisions,decisions.
The chemistry of the matter may
be way down there on your list of
concerns, but we’ll try to raise it a
few notches by sharing the following
article that appeared in Chemical &
Engineering News. Author Linda
Raber offers her own colorful
experiences. After that, it’s up
to you.
asked, “What’s that stuff?” he said he didn’t know. “You have
the chemistry degree,” he reminded me. A little while later,
with ammonia and other smells in the air, I didn’t need a
degree to tell me that there was some serious chemistry
going on up there.
Curious, I began looking around and found out that
there is some pretty interesting chemistry involved in coloring
hair. Here is what I learned: People have been changing the
color of their hair for millennia, but it wasn’t until 1907 that
French chemist Eugène Schueller created the first safe commercial hair coloring. His invention was based on pphenylenediamine. It later provided the foundation for his
company, the French Harmless Hair Dye Co., which was to
become L’Oréal.
There are several basic types of hair dyes on the market.
Temporary hair colors are applied in the form of rinses, gels,
mousses, and sprays. They coat the surface of the hair and
www.chemistry.org/education/chemmatters.html
HAIR STRAND PHOTO FROM ACS STOCK/PHOTODISC
usually wash out within two or three shampoos. Semipermanent dyes penetrate into the hair shaft, but not as deeply
as permanent dyes. Although semipermanent dyes do not
rinse off with water, they do fade and wash out of hair
after about 5 to 10 shampoos.
Gradual or progressive dyes—like Grecian Formula
16—surprised me. They are usually marketed to men
and contain lead acetate [Pb(CH3COO)2]. As the solution is rubbed on the hair, it penetrates the cuticle
and the Pb2+ ions react with sulfur atoms in the
proteins to form lead sulfide (PbS), which is
dark in color. The more frequently the solution
is applied, the darker the— ahem—lead head.
The most interesting chemistry to me, however, was the chemistry of permanent hair dyes—especially those that lighten and color in one process. These
formulations penetrate deeply into the hair shaft and don’t wash
out.
Before any permanent color can penetrate the hair shaft, the cuticle, or outer layer, must be opened so that chemicals can get to the
natural pigment molecules. Under a microscope, a cuticle of human
hair looks a lot like overlapping snake scales. The pigments, which are
protein granules, are stored in the cortex of the hair beneath the scaly
cuticle layer.
There are two types of melanin protein found in the hair: eumelanin, which is responsible for hair shades from black to brown, and
phaeomelanin, which is responsible for red and yellowish colors.
Absence of pigment, which was my problem, produces white or gray
hair. The melanin type and granule size determine the color of hair,
while the density of distribution of these pigment granules determines
how light or dark the hair is. But enough on natural hair color.
Permanent hair-coloring products consist of two components that
are packaged separately and mixed together immediately before application. One package contains a solution of hydrogen peroxide (usually
PHOTO COURTESTY OF LINDA RABER
PHOTO FROM GETTY IMAGES
ILLUSTRATION BY CESAR CAMINERO
6%) in water or a lotion base. The other
package usually contains an ammonia
solution of dye intermediates and preformed dyes—called couplers. The primary intermediates are ortho- or paradiaminobenzenes, aminohydroxybenzenes,
and to a lesser extent, dihydroxybenzenes,
which develop color on oxidation. The
color couplers don’t oxidize readily but
react with the oxidized primary intermediates to provide a wider variety of colors.
The couplers are phenols, meta-disubstituted phenylenediamines and phenyleneaminophenols, and various resorcinol
(1,3-dihydroxybenzene) derivatives.
As soon as the ammonia dye solution and the hydrogen peroxide solution
are mixed together, they are applied to
the hair. The ammonia in the mixture
(less than 1% concentration) causes the
hair to swell and the cuticle scales to separate a little.
After this happens, the dye precursors are able to penetrate the cuticle before they have fully reacted with
each other and with the hydrogen peroxide. This is
why even when brown hair coloring is first applied it
looks whitish. This is also why you have to wait a half
hour or more for the color to develop.
Darker shades are obtained by using higher concentrations of intermediates. Tones can also be
adjusted. For example, addition of resorcinol will
make a shade more yellow, whereas adding 4amino-2-hydroxytoluene will make the shade redder.
Sometimes dyes are used along with the oxidation dye
intermediates to add vibrancy to the tone that is not otherwise available. Usually, these dyes are used to add intensity to
gold or red shades.
I never had a desire to look like Lucille Ball, so I don’t think I’m
going to go for red hair, but if I did, the formulation used most likely
would contain 2-nitro-p-phenylenediamine. I understand that this
orange-red color would be quite bright and that the narrower absorption spectrum of this dye produces much purer hair color than the
broader visible absorption bands of other dyes. Sounds intense.
I’m glad I have all these choices and don’t have to be gray-haired
before I want to be. Let’s hear it for better—and blonder—living
through chemistry!
Linda Raber is a writer on the staff of Chemical &
Engineering News at the American Chemical Society in
Washington, DC.
REFERENCE
Raber, L. What’s That Stuff? Chemical &
Engineering News, March 13, 2000, pp 52–53.
ChemMatters, APRIL 2002 11
MysteryMatters
By Roberta Baxter
The first World Trade
Center attack
Even before the horror of the September 11, 2001, disaster, the
World Trade Center was the target of another terrorist attack—a bombing that killed six people in New York City on February 26, 1993.
When bomb experts from the New York Police Department, the FBI,
and the Bureau of Alcohol, Tobacco, and Firearms examined the destruction caused by the massive explosion under Tower One of the World
Trade Center, they concluded it was caused by a bomb—not a natural
gas or transformer explosion. The wreckage became the crime scene,
and the hunt for the source was on.
Crawling into the debris in hazardous materials suits, forensic
chemists swabbed surfaces around and in the wreckage to determine
the chemical makeup of the bomb. They analyzed collected samples
12 ChemMatters, APRIL 2002
PHOTO SOURCE: SCIENCE IN A TECHINICAL WORLD, © ACS
“T
here’s always a clue!” says Gill, the head of the crime
scene investigation unit on the popular TV drama CSI.
The series and several others like it feature the work of
forensic scientists, often portrayed using techniques that might look
familiar to you as you learn your way around a chemistry lab.
Just like a scientist setting up a controlled experiment, an investigator, upon arriving at the crime scene, secures the site so that no evidence is lost or contaminated. A loose hair from a careless investigator
might wind up being tagged as evidence along with other hairs. A person
tracking mud introduces extraneous substances while obliterating the
real evidence. So, right away the yellow tape goes up and bagging the
evidence begins.
Bombing, murder, and poisoning? All in a day’s work for our
crime scene investigators who tap the knowledge, skills, and tools
from many sciences as they methodically sift through the evidence.
Besides chemistry, there’s often biology, genetics, and metallurgy
going on at the scene.
Take a bombing case for an example. Most of us wrongly assume
that an explosion destroys all of the evidence of a bomb. But in reality,
bombs leave many clues. Photographs and measurements record a pattern of destruction and may reveal where the bomb was detonated, as
well as the explosive power it packed. Bomb residues, fragments, a
timer, and a container are all carefully sought and analyzed to determine
the type of bomb.
Forensic analysis must be accurate and reliable.
with an infrared microspectroscope, a powerful microscope designed to
use visible light to pinpoint a miniscule part of a sample before further
analyzing it by infrared spectroscopy. Results showed that the bulk of
the explosive force came from a mixture of urea (NH2CONH2) and nitric
acid (HNO3).
Molecules absorb infrared radiation at unique frequencies. These
distinctive absorption fingerprints are especially useful to forensic
chemists for identifying substances. Solutions are injected into the
infrared spectroscope. The resulting readouts show distinctive peaks for
each type of molecule at the frequencies at which they absorb the radiation. The pattern made by these peaks can be compared with those of
known substances.
In the 1993 World Trade Center bombing investigation, the trail of
evidence soon led investigators to a storage locker rented by one
Mohammed Salameh. FBI officials found urea, nitric acid, sulfuric acid,
and fuses—all the makings of the bomb that had killed six people and
caused damage reaching into the millions of dollars. This chemical evidence, combined with other findings, eventually resulted in the conviction of Salameh and three other conspirators.
www.chemistry.org/education/chemmatters.html
Poisoning cases sometimes require sophisticated analytical methods, sometimes even the examiner’s nose! In 1986, a woman in Seattle
took two Excedrin capsules and died within minutes. An alert medical
examiner at the crime scene detected the smell of almonds, an indication
of the presence of cyanide (CN¯), a deadly poison. Toxicology reports
confirmed the finding, and detectives found other poisoned capsules in
the bottle.
Soon afterward, police received a call from another woman. Her
husband had died a week earlier. Although his death had been ruled “natural”, she claimed that he too had been poisoned by adulterated
Excedrin. Was she right? Analysis of Excedrin capsules in their home
showed they contained cyanide, and an analysis of some blood from her
husband’s body tested positive. Case closed?
Not quite! Forensic chemists were curious about some green
specks found in her Excedrin bottle and decided to analyze their composition using a mass spectrometer, an instrument that ionizes materials
before passing them through a magnetic field. Ions differ from one
another by how their paths bend in the field.
The curious green specks were found to be about 99% sodium
chloride (NaCl), common table salt. But the remaining 1% was a combination of four chemicals used to fight algae growth in aquariums.
The connection gradually became clear. Police determined that the
woman had purchased the aquarium chemicals at a local outlet and had
ground them up using a mortar and pestle. Later, she used the same
mortar and pestle to grind up the cyanide that killed her husband.
The alleged murder motive was complex. A death due to poisoning
would be ruled accidental, resulting in a higher life insurance award.
When his death was first attributed to natural causes, she was frustrated.
She ground up cyanide and added it to capsules of Excedrin. Then she
placed them on the shelves of a local drug store. When the other victim’s
death was reported, she hoped to claim that her husband’s death was
caused by the same unknown murderer.
PHOTOS FROM ACS STOCK, DIGITAL STOCK
Time since death
An autopsy may reveal the history of a violent attack in the form of
wounds, bruises, and broken bones. But what happens when the victim’s
body has been buried or disposed of in such a way that the discovery is
delayed, sometimes for months or even years?
“How long will a man lie i’ the earth ere he rot?” Hamlet asks in
Shakespeare’s play. Researchers from the Oak Ridge National Laboratory
and the University of Tennessee–Knoxville have been studying this problem for several years. Mystery novelist Patricia Cornwell’s best-selling
novel The Body Farm details the work of the forensics facility and, to the
dismay of the staff, the name stuck. Arpad Vass, a biochemist at the
facility, feels that “body farm” is disrespectful to those who have donated
their bodies for forensic research.
PHOTO SOURCE: SCIENCE IN A TECHINCAL WORLD, © ACS
Telltale green specks
Proper handling of evidence is essential in legal cases.
Vass and graduate student Jennifer Love conduct research to find
chemical methods for arriving at a precise time since death (TSD). The
more exact the TSD, the easier it becomes for a crime investigator to
spot a fictitious alibi.
At the laboratory, researchers place human bodies in shallow
graves, car trunks, and plastic bags—all potential sites for finding the
remains of violent crimes. Vass and Love take daily readings of tissue
deterioration, aromas, and underlying soil composition.
At death, the proteins in the body begin to break down into amino
acids and volatile fatty acids. Vass developed a method for tracking four
fatty acids: valeric, propionic, and the straight and branched types of
butyric acid. The ratio of these acids in the soil around a body fluctuates
on a daily basis as the body decays. By collecting data under various
moisture and temperature conditions, the researchers are refining the
accuracy of a chemical “clock” for reporting the TSD. Using a combination of methods, Vass hopes to get the TSD determination down to hours
rather than days.
Using scientific methods and tools that would be the envy of Sherlock Holmes, forensic chemists sift through evidence with compelling
accuracy. And you may be surprised at this: Modern chemical evidence
is used more often to free wrongly convicted persons and to exonerate
innocent suspects than it is used to convict the guilty.
Roberta Baxter is a freelance writer from Colorado Springs, CO. Her latest
ChemMatters article “Chocolate: How Sweet It Is!” appeared in the December
1999 issue.
REFERENCES
Atkinson, W. I. Expanding the Scope of Forensic Science. Today’s
Chemist at Work, October 2000, pp 44–52.
Cornwell, P. The Body Farm; Scribners: New York, 1994.
Dwyer, J.; Kocieniewski, D.; Murphy, D.; Tyre, P. Two Seconds Under
The World; Crown Publishers: New York, 1994.
Fisher, D. Hard Evidence: How Detectives Inside the FBI’s Sci-Crime
Lab Have Helped Solve America’s Toughest Cases; Simon &
Schuster: New York, 1995.
Maples, W. R.; Browning, M. Dead Men Do Tell Tales; Doubleday:
New York, 1994.
Martindale, D. Bodies of Evidence. New Scientist, January 6, 2001,
pp 24–28.
ChemMatters, APRIL 2002 13
By Jay Withgott
S
tissues reflects the ratio of isotopes present in their home environments.
Ehleringer calls these records in plant tissues “fingerprints of the world”.
It works like this. Whether the plant grew in wet or dry soil might be
determined by looking at the nitrogen. How? Wetter soil hosts more bacterial activity. Because bacteria prefer the nitrogen-14 isotope, they leave
behind more nitrogen-15 in the soil for plants to pick up. So plants in
wetter climates incorporate more nitrogen-15 than plants growing in
drier climates.
Mapping the drug traffic
Carbon isotopic ratios in the air vary slightly with humidity. In
humid conditions, plants keep their stomata (tiny breathing pores on the
surface of leaves) open, letting in air loaded with more carbon-13 than
would be present in drier air. As a result, plants from drier Bolivia have a
different isotopic “fingerprint” than plants from wetter Colombia.
By adding information about some trace soil alkaloids that seem
to favor certain growing locations, Ehleringer’s methods gained reliability. Combining data on isotope ratios and trace chemicals, the group
was able to produce a chemical map of the different South American
growing regions.
The DEA wanted to know the geographical origin of cocaine that it
confiscated, Ehleringer says, to determine shipment routes and also “to
get a measure of whether their interdiction efforts were having an
impact.” So Ehleringer and his DEA colleagues collected samples of coca
leaves and purified cocaine from numerous locations throughout South
America. Then they analyzed the carbon and nitrogen in each sample.
As plants grow, they pick up molecules from the soil, water, and air,
incorporating them into their tissues. As a result, the chemistry of these
14 ChemMatters, APRIL 2002
SOURCE: DEA PRESS RELEASE WWW.DEA.GOV
core one for the war on drugs! But was the cocaine really grown
in Colombia? Or might it be traced to other growers, maybe in
Bolivia or Peru? If you’re with the Drug Enforcement Agency
(DEA), those are important questions. The answers? That’s where
chemistry comes in. Whether it’s illicit drugs like cocaine or illegal
imports of agricultural items like peanuts, chemists are helping U.S.
government agencies track the sources of supply.
Chemistry detectives look at trace elements, often noting the ratios
of their stable isotopes. Many elements possess multiple stable isotopes—versions of the same element with varying numbers of neutrons,
and thus different masses. As living tissues grow, certain conditions—
like temperature and humidity—can favor the inclusion of some isotopes
over others.
Ecologists see these isotopic ratios of carbon, hydrogen, oxygen,
and nitrogen as signatures. Using these signatures, they can reconstruct
diets, trace the paths of nutrients in food webs, and track animals that
migrate from one region to another. Now, chemists are even using isotopes to help the government enforce its laws.
James Ehleringer, an analytical chemist at the University of Utah,
welcomes the opportunity to apply his basic research findings on isotopes to solving some important problems facing our society. The
government first called on Ehleringer’s services to devise methods for
detecting counterfeit currency—efforts that eventually led to the
design of new currency bills introduced in recent years. Next
Ehleringer tackled cocaine.
www.chemistry.org/education/chemmatters.html
www.chemistry.org/education/chemmatters.html
--4 -—
-3 -—
-2 -—
-1 -5 -—
On the trail of smuggled groceries
When it comes to agricultural products, Schwartz is the man to see.
How does he track down the origins of illegal imports? Schwartz looks
for distinct patterns of trace elements—chemicals, generally metals, that
occur naturally in extremely low concentrations. And, as with isotope fingerprints, trace element signatures can map the geographic origins of
the plant.
Schwartz uses a mass spectrometer (MS), which detects and measures masses of different atoms contained in the sample. The more elements are measured, the more reliable differences turn up to distinguish
samples from different regions. That’s why Schwartz tries to detect all
the trace elements he can from each sample. With the present technology, he estimates his machinery gathers data on up to 65–70 trace elements, of which up to 35–40 are distinct enough to provide strong clues.
Once the MS has done its duty, Schwartz puts the data through statistical analyses capable of handling large numbers of variables at once.
Patterns soon emerge among them. Schwartz focuses on the elements
that are the most informative (it varies from product to product), and
uses data from these to categorize the samples into groups. As in isotope work, the first step is to analyze reference samples from diverse
geographic areas—something made more feasible when you’ve got the
long arms of the U.S. government collecting samples for you.
“The reference samples create sort of a fingerprint,” Schwartz says,
“and once you’ve [analyzed them], you’re in a position to analyze
unknown or suspect samples.” So far, he says, he’s been able to determine origins with more than 90% accuracy.
Schwartz’s biggest projects to date involve peanuts. In one study,
he kept watch for peanuts from China after the U.S. Department of Agriculture had banned their import because of a virus. When the North
American Free Trade Agreement (NAFTA) was coming up for a vote in
1993, U.S. peanut farmers feared that if duties were abolished for Mexican peanuts, other countries would try to sneak their product into the
United States through Mexico, thus flooding the market and undercutting prices with peanuts our country had not agreed to import for free.
The worried farmers pressured Congress to vote NAFTA down.
Customs came in to broker a deal. The agency promised to institute a
testing program to guard against non-Mexican peanuts. That’s where
Schwartz came in. He started by analyzing hundreds of reference
samples from around the world to get a global picture of the trace
element diversity in peanuts. In the end, it turned out the farmers had
little to worry about. Schwartz found that very few peanuts were
being smuggled.
Whether it’s winning the war on drugs or keeping food safe and
affordable, chemists like Ehleringer and Schwartz are continuing to
refine their methods for mapping the sources of supply.
Jay Withgott is a science writer and journalist based in San Francisco, CA. His
most recent ChemMatters article “Lead—Beethoven’s Heavy Metal Ailment”
appeared in October 2001.
REFERENCES
Ehleringer, J. R.; Casale, J. F.; Lott, M. J.; Ford, V. L. Tracing the
Geographical Origin of Cocaine. Nature 2000, 408, 311–312.
Gorman, J. Chemistry Catches Cocaine at Source. Science News,
Nov 18, 2000, p 324.
Gugliotta, G. Customs Chemist’s Test Roots Out Illegal Imports. The
Washington Post, June 28, 1999, p A09.
ChemMatters, APRIL 2002 15
PHOTO FROM ASC STOCK/PHOTODISC
Then it was time for a test. Ehleringer’s group analyzed samples
with origins known to the DEA agents but not to the chemists—a multiple-choice test, as it were. They passed with flying colors, correctly
determining the origin of samples roughly 96% of the time.
While DEA chemists work to further refine the cocaine map,
Ehleringer is pursuing similar research on heroin. Heroin consists of
morphine—a natural plant product of poppies—chemically reacted with
acetic anhydride (CH3CO)2O. The work begins by reversing the reaction,
stripping away the acetic anhydride so the pure morphine can be analyzed—which is not always easy, Ehleringer says. Although cocaine is
easily purified, “with heroin, you have everything in there but the kitchen
sink and the living room sofa.”
Nevertheless, Ehleringer and his crew are now able to differentiate
samples from three major growing regions—southwest Asia (such as
Afghanistan and Pakistan), southeast Asia (such as Burma and Thailand), and Latin America (such as Mexico).
Presently, Ehleringer is training chemists from a variety of government agencies to do this type of work—from the Federal Bureau of
Investigation to the Bureau of Alcohol, Tobacco, and Firearms to the
Secret Service to the Customs Service. “It’s just to let people know
there’s another tool in the arsenal. It’s not a silver bullet,” he says.
Maybe not, but the work is proving to be a powerful tool!
Meanwhile, over at the U.S. Customs Service, another analytical
chemist traces the origins of illegal substances coming across our borders. But Robert S. Schwartz, senior research chemist at a U.S. Customs
research laboratory in Springfield, VA, doesn’t analyze drugs. His attention is focused on illegal imports of items like peanuts, garlic, coffee, and
orange juice. Orange juice can be illegal? Sometimes, for reasons of
safety, economics, or politics—yes.
Customs is responsible for watching what comes into the country,
so it tries to stop products that are a threat to health and safety. But it
also polices international trade agreements that the United States has
made with other countries, watching for products trying to sneak in that
could unfairly threaten the profits of U.S. companies and farmers.
Generally, a product’s composition—its purity or quality—affects
the tariff that the government applies. A more valuable import gets taxed
more. Thus, foreign producers sometimes try to mask the quality of their
products. Often it’s the opposite. A low-quality product masquerades as
a more valuable one for a better price at market. Customs chemists have
even been called on to identify counterfeit perfumes.
Chem.matters.links
A whole year of
chemistry before
your eyes
Spring is here, and final exams
are coming all too soon!
Here’s a suggestion for a lively
review of all those
topics
Tracking down
the evidence
The FBI maintains a Web site
for informing citizens of current
cases under investigation,
career information, and fascinating details about famous
casework. But the page that we
1155 Sixteenth Street, NW
Washington, DC 20036-4800
Reach Us on the Web at
www.chemistry.org/education/chemmatters.html
like best is entitled the
Handbook of Forensic Services
at www.fbi.gov/hq/lab/
handbook/examlist.htm. Here
you’ll find a guide for working
crime scene investigators as
they identify, isolate, and analyze evidence. Go to the Crime
Scene link to find out about
the importance of keeping collected materials free of contamination.
ucts for men. “Grecian water”
used to dye the mustache a silver gray was a silver nitrate
mixture that, after repeated
uses, turned the hair purple.
These and other fascinating
hair dye facts are available at
www.hairboutique.com/tips/
InProgress/tip892.htm.
Up and away
Hair dye history
Did you know that the
ancient Gauls dyed their hair
red to denote class rank, but
by the Middle Ages, red
hair was thought to
be a sign of
witchcraft?
And while the
ancient Romans
decreed that “women of the
night” must dye their hair
blonde, Renaissance customs
made blonde hair a sign of
angelic purity. To achieve the
“pure” look, Renaissance
women applied a
mixture of
black sulfur,
alum, and
honey
before
spreading
their tresses
out to bleach
in the sun. By
1825, there
were hair
dye prod-
ILLUSTRATION FROM ACS CLIP ART STOCK
www.caves.org is the
Web home of the National
Speleological Society (NSS), a
group of 12,000 caving enthusiasts throughout the United
States. The Web site is extensive, linking to beautiful photographs, news of activities,
guides for getting started in
caving, and even haunting
cave sounds and ballads for
downloading. But there’s a
serious side to all of these
offerings. The NSS is concerned about preserving the
delicate beauty of these underground treasures. Too many
colorful speleothems end up
as broken pieces for sale in
rock shops, and too many caverns become littered with
garbage and graffiti.
and concepts you’ve encountered along the way. Go to
www.whfreeman.com/
chemcom and select the first
link for an interactive multimedia tour. You may need to
install a couple of free plug-ins,
but, once that’s done, you’ll
find yourself on an interactive
and fun overview of your entire
chemistry course—from atoms,
to ions, to reactions, and
beyond. The site is designed to
introduce and acquaint teachers with a feature of the new
edition of Chemistry in the
Community, a widely used high
school textbook developed by
the American Chemical
Society. But you’re welcome to
come on in and make use of
the media. We’d like to hear
what you think of it. After taking a tour, write us at
[email protected].
Here’s another thorough
review site: http://dbhs.
wvusd.k12.ca.us/ChemTea
mIndex.html. This site, which
is a little more traditional, is
maintained by the chemistry
department at Diamond Bar
High School in California.
PHOTO FROM ACS STOCK, PHOTODISC
Cyber caving
Our instructions for constructing and launching a hot
air balloon are just enough to
get you started. If your
class is
ready to
travel
wherever
the physics and
math may lead,
check the
extensive
guide for balloon making and
launching at
www.overflite.
com/science.html.
And if hot air gets into
your blood—figuratively
speaking!—you can check the
Aerostar Web site at
www.aerostar.
com for advice on getting
involved with other balloonists
as crew members. Balloon
pilots are licensed by the
Federal Aviation
Administration, and the
requirements are extensive.
®
APRIL 2002
Caves
Chemistry goes
underground.
Hot Air Balloons
Make and launch your own!
Hair Coloring
Discover formulas to dye for.