December, 2001
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® DECEMBER 2001 Fragrances and Smells This chemistry gets personal! The Feast of Luminol KING MIDAS A simple spray casts a revealing light on crime. Chemists analyze the leftovers. Question From the Classroom By Bob Becker 1 2 3 Q. Do ducks get cold feet? A. If you have ever watched The fact is that the ani- temperature (42 °C), mal’s blood supply has then lose a huge a duck paddling its way No heat Maximum through frigid water on a already been cooled consider- amount of heat to the exchange heat winter day, this question may ably before it ever reaches the cold water as it exchange have occurred to you: Why feet. There’s not much energy passed through all Some heat exchange don’t ducks get cold feet? The left in the webbed feet to be the small capillaries, answer is actually quite drained away by the high heat- delivering its oxy- simple. They do. In fact, their capacity water. Likewise, the gen to every cell in feet and the blood inside them returning blood has already the duck’s foot. The get nearly as cold as the been warmed before it re- blood would then surrounding water. How can enters the body. As a result, travel back toward they stand it? Perhaps they virtually no energy is wasted the heart at 2 °C, Heat lost through feet to icy water have few nerve endings in as the duck’s body maintains and, assuming the their feet, or perhaps, they its internal temperature while duck could sur- and a little less energy needed have simply grown to LIKE paddling through icy water. vive this shock, it would to rewarm the blood. This plan having cold feet! How does the duck man- require an enormous amount would be a definite survival A better question to ask, age that? It all has to do with of energy to warm the blood advantage for any duck with however, is how do they sur- something called countercur- back up to 42 °C. such a circulatory system. vive it? How can ducks—or rent heat exchange, and it Now let’s make one small Actually, the duck swim- any other warm-blooded ani- relies on the extensive net- adjustment. Let’s place the ming in icy water operates on work of veins and arteries in vein and artery closer togeth- a fine-tuned version of this mals—afford to lose that ILLUSTRATION BY CESAR CAMINERO much heat to their surround- the duck’s legs. A duck’s body er, as shown in the second heat exchange plan. The third ings? Here’s where the story temperature runs about 42 °C pattern in the figure. Now pattern in the figure shows gets intriguing. It turns out (108 °F), and the water in there is a way for transferring how the blood vessels in a that they don’t! You might which it is swimming is often some heat from the outgoing duck’s legs are arranged. expect that those webbed feet just above freezing—say 2 °C 42 °C blood to the returning Veins and arteries are finely with all their exposed surface (35 °F). Suppose the duck just 2 °C blood. As the outgoing divided and interwoven so as area would allow for all sorts had one main artery running and incoming blood pass each to ensure maximum contact of heat loss. And you would from its body to each foot, other, the cold blood warms and maximum heat transfer also think that a lot of pre- and one main vein, completely up and the warm blood cools between the outgoing warm cious energy from the metab- separated, running back to the down. Even if the exchange blood and the returning cold olism of food would be spent body. results in only a few degrees blood. With such extensive reheating the chilled blood As shown in pattern 1 in of temperature change, there contact between veins and flowing back into the duck’s the figure, the blood would would still be a little less heat arteries, the warm blood leav- body. enter the foot at the full body lost to the surrounding water ing the body cools to nearly 2 °C as it travels down the tus for federal income tax purposes leg. Likewise, the cold blood Statement of Ownership, Management, and have not changed in the past 12 leaving the foot warms up to Circulation for ChemMatters Magazine months. 45,000 copies of each maga- nearly 42 °C as it travels up zine issue are printed. Average circula- tion during the past 12 months was the leg. ChemMatters is published quarterly by the 30,621. Circulation closest to the filing date was It works great! By this coun- American Chemical Society, 1155 16th St., NW, 14,845. There are no paid in-county subscriptions, tercurrent heat exchange, the Washington, DC 20036. Both the office of publica- no sales through dealers or vendors, and no other tion and the general business office are at USPS mailings at other classes. There is no free duck loses only a minimal American Chemical Society, 1155 16th St., NW, distribution of ChemMatters. During the past 12 amount of heat from its feet, Washington, DC 20036. Editor: Michael J. months, an average of 14,379 magazines per issue and it needs only a minimal Tinnesand; Managing Editor: Helen G. Herlocker. were not distributed. For the most recent issue Owner: American Chemical Society. There are no (October 2001) 30,155 were not distributed. This amount of energy to warm the other known bondholders, mortages, and other statement was filed according to Section E216.3.0 blood back up. Our refrigera- security holders. The purpose, function, and non- of the USPS Domestic Mail Manual on October 1, tors and heat pumps should profit status of this organization and its exempt sta- 2001, by Michael J. Tinnesand, Editor. work so well. 2ChemMatters, DECEMBER 2001 ® Vol. 19, No. 4 DECEMBER 2001 DEPARTMENTS Question From the Classroom 2 Do ducks get cold feet? Well, maybe this isn’t the question on everyone’s mind, but it is curious how ducks can paddle around in near-freezing water without so much as a shiver! ChemSumer 8 How We Smell and Why We Stink Let’s be blunt. Humans are among the smelliest creatures on the planet, a fact not lost on manufacturers, who turn out hundreds of products designed to keep our natural aromas in check. MysteryMatters 12 PHOTO BY MIKE CIESIELSKI Luminol—Casting a Revealing Light on Crime FEATURES Sprayed with luminol, the suspicious stains glowed with an eerie King Midas: Leftovers From his Last Feast 4 blue luminescence. What once appeared as an ordinary home No longer even remotely edible, these 2000-year-old was now believed to be a crime scene. leftovers presented analytical chemists with an interesting ILLUSTRATION BY DAN SHERBO challenge. They not only figured out the ingredients, they Chem.matters.links 16 even came up with the recipes. Link to some ancient recipes for serving up your own royal feast. Trolling the Seas for New Medicines 6 All living things trace their origins to the sea. Now drug researchers find that the oceans contain chemical treasures for curing illnesses and maintaining health. COURTESY OF AMY WRIGHT Hypothermia—Surviving the Big Chill 14 For cold that goes beyond a frosty morning, the human body resorts to some effective strategies to stay alive. TEACHERS! FIND YOUR COMPLETE uzzler TEACHER’S GUIDE FOR THIS ISSUE AT CM P www.acs.org/education/curriculum/chemmatt.html. How is the top of your head like a duck’s foot? Find the answer in this issue of ChemMatters! COVER PHOTO BY MIKE CIESIELSKI Production Team Division of Education and American Chemical Society at 1155 statements and opinions advanced Helen Herlocker, Managing Editor International Activities 16th St., NW, Washington, DC by contributors. Views expressed Cornithia Harris, Art Director Sylvia Ware, Director 20036-4800. Periodicals postage are those of the authors and do not Leona Kanaskie, CMCopy Editor Janet Boese, Assistant Director for paid at Washington, DC, and addi- necessarily represent the official tional mailing offices. POSTMAS- Administrative Team Academic Programs position of the American Chemical TER: Send address changes to Michael Tinnesand, Editor Policy Board Society. Julie Farrar, Creative Director Susan Cooper, Chair, LaBelle ChemMatters Magazine, ACS Office All rights reserved. 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