October 11, 2010 Vol. 88, Issue 41 Fix-A-Flat

October 11, 2010
Vol. 88, issue 41
Fix-A-Flat
September 6, 2010
Vol. 88, issue 36
Road Markings
August 9, 2010
Vol. 88, issue 32
Trick Candles
March 29, 2010
Vol. 88, issue 13
Body Armor
March 22, 2010
Vol. 88, issue 12
Wasabi

January 25, 2010
Vol. 88, issue 4
Hand Warmers
October 26, 2009
Vol. 87, issue 38
Silly String
August 24, 2009
Vol. 87, issue 34
Sports Drinks
June 29, 2009
Vol. 87, issue 26
Dental Anesthetics
April 13, 2009
Vol. 87, issue 15
Self-Darkening Eyeglasses

March 23, 2009
Vol. 87, issue 12
Instant Film
March 2, 2009
Vol. 87, issue 9
Synthetic Grass
December 22, 2008
Vol. 86, issue 51
Frankincense And Myrrh
November 17, 2008
Vol. 86, issue 46
Contact Lens Soulutions
October 27, 2008
Vol. 86, issue 43
Plasma Globes

September 29, 2008
Vol. 86, issue 39
Instant Coffee
August 11, 2008
Vol. 86, issue 32
Nail Polish
July 7, 2008
Vol. 86, issue 27
Bowling Balls
June 16, 2008
Vol. 86, issue 24
Liquid Bandages
April 14, 2008
Vol. 86, issue 15
Dryer Sheets

March 17, 2008
Vol. 86, issue 11
Contact Lenses
February 18, 2008
Vol. 86, issue 7
Lava Lamps
January 7, 2008
Vol. 86, issue 1
Excipients
November 12, 2007
Vol. 85, issue 46
Tattoo Ink
October 15, 2007
Vol. 85, issue 42
Adhesive Tape

September 24, 2007
Vol. 85, issue 39
Oil Paints
August 6, 2007
Vol. 85, issue 32
Chewing Gum
July 23, 2007
Vol. 85, issue 30
Sandpaper
July 9, 2007
Vol. 85, issue 28
Leather
June 18, 2007
Vol. 85, issue 25
Pool Chemicals

March 12, 2007
Vol. 85, issue 11
Amber
February 5, 2007
Vol. 85, issue 6
Honey
October 30, 2006
Vol. 84, issue 44
Citronella Oil
August 21, 2006
Vol. 84, issue 34
Chicken Eggs
June 12, 2006
Vol. 84, issue 24
Rain Coats

April 17, 2006
Vol. 84, issue 16
Marshmallow
April 3, 2006
Vol. 84, issue 14
Beer
March 13, 2006
Vol. 84, issue 11
Motor Oil
February 6, 2006
Vol. 84, issue 6
Henna
January 9, 2006
Vol. 84, issue 2
Polyurethane Foam

November 14, 2005
Vol. 83, issue 46
Kava
August 1, 2005
Vol. 83, issue 31
Catnip
July 18, 2005
Vol. 83, issue 29
Golf Balls
May 16, 2005
Vol. 83, issue 20
Whisky
February 21, 2005
Vol. 83, issue 8
Gasoline

November 8, 2004
Vol. 82, issue 45
Ice Cream
September 20, 2004
Vol. 82, issue 38
Plastic Bags
August 16, 2004
Vol. 82, issue 33
Margarine
June 21, 2004
Vol. 82, issue 25
Artificial Sweeteners
April 26, 2004
Vol. 82, issue 17
Kitty Litter

April 5, 2004
Vol. 82, issue 14
Sticky Notes
January 19, 2004
Vol. 82, issue 3
Artificial Snow
January 5, 2004
Vol. 82, issue 1
Champagne
November 24, 2003
Vol. 81, issue 47
Glass
November 3, 2003
Vol. 81, issue 44
Chili peppers

August 25, 2003
Vol. 81, issue 34
Food Coloring
July 28, 2003
Vol. 81, issue 30
MSG
May 19, 2003
Vol. 81, issue 20
JELL-O®
April 28, 2003
Vol. 81, issue 17
Soap Bubbles
February 10, 2003
Vol. 81, issue 6
Teeth Whiteners

January 27, 2003
Vol. 81, issue 4
Opal
December 16, 2002
Vol. 80, issue 50
Erasers
November 11, 2002
Vol. 80, issue 45
Food Preservatives
August 12, 2002
Vol. 80, issue 32
Licorice
August 5, 2002
Vol. 80, issue 31
Bug Sprays

June 24, 2002
Vol. 80, issue 25
Sunscreens
May 20, 2002
Vol. 80, issue 20
New Car Smell
April 15, 2002
Vol. 80, issue 15
Shampoo
December 3, 2001
Vol. 79, issue 49
Shower Cleaners
November 5, 2001
Vol. 79, issue 45
Pasteurized Foods

October 15, 2001
Vol. 79, issue 42
Pencils & Pencil lead
July 2, 2001
Vol. 79, issue 27
Fireworks
April 16, 2001
Vol. 79, issue 16
Fluoride
January 1, 2001
Vol. 79, issue 1
Aircraft Deicers
December 4, 2000
Vol. 78, issue 49
Chocolate

November 27, 2000
Vol. 78, issue 48
Silly Putty
August 14, 2000
Vol. 78, issue 33
Paper
June 12, 2000
Vol. 78, issue 24
Self-Tanners
March 13, 2000
Vol. 78, issue 11
Hair Coloring
February 7, 2000
Vol. 78, issue 6
Cheese Whiz

November 22, 1999
Vol. 77, issue 47
Asphalt
February 15, 1999
Vol. 77, issue 7
Lycra/Spandex
July 12, 1999
Vol. 77, issue 28
Lipstick
March 29, 1999
Vol. 77, issue 13
Baseballs
January 4, 1999
Vol. 77, issue 3
Lightsticks

August 9, 2009 Volume 88, Number 32 p. 34

Trick Candles

A little magnesium dust ignites surprise at birthday parties

Linda Wang

Top of Form

Bottom of Form

Linda Wang/C&EN

It’s a familiar scene at birthday celebrations: The guest of honor blows out the candles on his or her birthday cake. Thin ribbons of smoke escape from the wicks, signaling the guests to clap and cheer.

But wait! The wicks begin to glow a fiery red. They flicker, and suddenly the flames reappear. Looking bemused, the birthday boy or girl tries to blow out the candles—again and again, much to the delight of the onlookers.

Trick candles, also known as magic candles, can add a flash of spontaneity to any party. The chemistry that allows these candles to repeatedly reignite turns out to be surprisingly simple.

Candle wax is typically made from paraffin hydrocarbons, and the wick is usually braided cotton treated with a chemical salt solution to prevent the wick from being destroyed too quickly by the flames, says Bob Nelson, director of fragrance development at Yankee Candle. “Wick manufacturers are secretive about the exact formulations they use,” he adds.

In a trick candle, magnesium powder is incorporated into the candle’s wick. Magnesium is a highly reactive metal when powdered or sliced thinly. It can ignite at temperatures as low as 800 ºF (430 ºC). When the flame is blown out, the hot embers from the wick ignite the magnesium powder, producing tiny sparks. This, in turn, ignites the vaporized paraffin hydrocarbons, which relights the wick. The magnesium found lower down in the wick doesn’t burn because it is protected by the paraffin. Magnesium powder is used in trick candles because it is flammable at a lower temperature than other pyrophoric metals such as aluminum or iron.

Trick candles are so simple to make that video instructions are readily available on YouTube and other video-sharing sites. But experts caution that the simple fun of these candles belies the dangers they pose. “We’re very concerned about these candles because of the potential fire hazard,” says Barbara Miller, a spokeswoman for the National Candle Association, in Washington, D.C. “People think the candles are done, so they take them out of the cake and throw them in the trash. Suddenly their trash is on fire.”

Miller recommends thoroughly extinguishing the candles by running them under water to cut off the candle’s oxygen supply. “When I use the candles, I douse them in water and set them in my sink for an hour or two before I put them in the trash,” she says.

Canada has banned the sale and advertisement of trick candles since 1977. Trick candles are currently legal in the U.S., and they are typically manufactured in Asia. “I think it would be very difficult to ban them here in the U.S.,” says Miller. “Of all of the issues that people are dealing with in product safety, trick candles are way down on the list. Our best bet is to continually try to educate consumers about the potential fire hazards of these candles.”

Information on when trick candles were invented and by whom is difficult to track down, but C&EN found several patents related to the basic principle. For example, in a 1983 Japanese patent titled “Self-Ignited Candle,” inventor Toshio Takahashi describes a candle fuse made of aluminum, magnesium, or iron, or an alloy of those metals. In a 2003 U.S. patent, Earl M. Stenger describes his invention of a wind-resistant candle that contains wick fibers made of a pyrophoric material such as magnesium or a magnesium-aluminum blend.

Inventors continue to experiment with novelty candles, including those that burn with colored flames. These candles are typically made by incorporating metal salts into the candles, but so far the commercial potential of these candles has been limited. Nelson says that Yankee Candle had looked into colored-flame candles several years ago, but there were issues with proper burning in the prototypes they examined.

Ron Newman, director of research and development at Maesa Group, a beauty and home fragrance products manufacturer, says his company has also looked into colored-flame candles, but because of a lack of data on the toxicity of metal oxide emissions from such candles, the company is holding off on licensing the technology. “This is really an unknown area of emissions,” says Newman.

As for trick candles, the novelty never seems to wear off. At birthday parties everywhere, the candles, like their flames, just keep coming back.

Chemical & Engineering News

ISSN 0009-2347

January 25, 2010
Volume 88, Number 4 p. 36

Hand Warmers

Small packets of warmth work through a simple exothermic reaction

Topics Covered

Amanda Yarnell/C&EN (Both)

TOASTY Hand warmers can extend the winter fun.

Top of Form

Bottom of Form

For winter sports enthusiasts, hand warmers can mean the difference between calling it a day early and playing outside for as long as possible. In fact, anyone who braves cold temperatures might be tempted to try the little pouches that emit warmth within seconds of being exposed to air.

Hand warmers date back centuries to when the Japanese would use hot stones to warm their hands, says Keiko Ishikawa, a marketing manager of hand-warmer maker Mycoal USA. Portable hand warmers filled with hot ash were the version that followed, she says.

These days, disposable hand warmers turn up the heat in your mittens by means of an exothermic reaction that, in essence, just creates rust. Each pouch typically contains iron powder, salt, water, an absorbent material, and activated carbon. When the pouch is removed from its outer packaging, oxygen drifts across the pouch’s permeable covering. With salt and water present, the oxygen reacts with the iron powder located inside to form iron oxide (Fe2O3) and release heat.

The absorbent material can be vermiculite, pulverized wood, or a superabsorbent polymer such as polyacrylate. It helps retain the moisture so that the reaction can occur. The activated carbon helps to evenly disperse the heat produced, which can average 135 °F.

Although the chemistry of disposable hand warmers is simple, their engineering is more complicated. “You want to make this thing act quickly because people like to open up the packet and feel warm right away, but you also want it to last a long time,” says Joe Vergona, manager of engineering and product development for Grabber Performance Group, a Grand Rapids, Mich.-based company that sells hand warmers. For example, some hand warmers last seven hours, and others can last more than 24 hours.

To lengthen the time a hand warmer lasts, some companies opt to increase the amount of iron in the packet, Vergona says.

Another strategy is to experiment with the iron powder. “If you vary the raw materials in the warmer, you can change how quickly the reaction happens or how much of the warmer is reacted at one time,” Vergona adds. For example, the greater the surface area of the iron, the more it can react with oxygen to produce heat, he says.

The pouch material also affects the performance of the hand warmers. “It’s a balance of the ingredients inside the pack and the performance characteristics of the pouch itself,” Vergona says. The iron powder and other ingredients are contained in a blended nonwoven material that has specific permeability characteristics. If the pouch admits more oxygen, the reaction occurs more quickly. Toe warmers, for example, use a nonwoven material that lets in more oxygen to compensate for the low-oxygen environment inside a shoe. “The level of perforation, the size of the holes—all that’s going to govern how much oxygen enters the warmer,” Vergona says.

“You want to make this thing act quickly because people like to open up the packet and feel warm right away.”

To extend the shelf life of hand warmers, the outside wrapper is specially chosen to ensure that minimal amounts of oxygen get in and minimal water gets out. “Any old plastic, and the hand warmers will last a week and die,” because oxygen can get in and spoil the product, Vergona says. The outside wrappers are usually made of polymers such as the plastic polyethylene.

The main difference between disposable hand warmers and some reusable versions is the chemicals used to produce the heat-releasing reaction. Reusable hand warmers don’t contain iron but instead use a supersaturated solution of sodium acetate that releases heat as it crystallizes. Boiling the used packet restores the solution to its supersaturated state. Air-activated hand warmers can’t be reused.

Besides warming hands and feet, the technology has other applications. For example, Grabber sells heavy-duty warmers that can be used to transport tropical fish. The company is also expanding into the medical and therapeutic fields.

Hand warmers can even be used to teach exothermic reactions, as Kathy Ceceri, a mom who homeschools her children, discovered. The packaging instructions might have “said not to open the packet, but I immediately opened it and poured the contents into a glass jar,” she says, noting that the iron powder began to smoke. By completely exposing the iron to air, she accelerated the exothermic reaction.

Ceceri—and anyone else who’s used hand warmers—has discovered that there’s nothing like simple chemistry to help turn up the heat.

Chemical & Engineering News

ISSN 0009-2347

August 24, 2009

Volume 87, Number 34 p. 36

Sports Drinks

Balanced mixture of sugar, salt, and other additives keeps athletes going strong

Lauren K. Wolf

Bottom of Form

iStock

As triathlete Ryan Smith prepares for his third Ironman competition—an endurance event that includes a 2.4-mile swim, a 112-mile bike ride, and a full marathon—the chemical composition of his sports drink is at the top of his mind. But his use of the beverage to stay hydrated, maintain consistent performance during the race, and speedily recover afterward is actually a reasonably new phenomenon.

As recently as the early 1960s, coaches typically advised their athletes to ignore thirst. But a 1965 study conducted by a group of scientists at the University of Florida changed everything: The researchers discovered that players on the school’s football team, the “Gators,” were suffering from heat exhaustion and suboptimal performance because of dehydration and a loss of electrolytes and carbohydrates from exercise. As a result, the scientists formulated a sugar-salt replacement beverage—eventually dubbed Gatorade—and administered it to the team, which went on to win the Orange Bowl in 1966.

Fluid replacement sports drinks have since grown to be at least a $3.5 billion market in the U.S., according to Chicago-based market research firm Information Resources. But they are still “essentially water, sugar, salt, and some flavoring and coloring,” says Edward F. Coyle, director of the Human Performance Laboratory at the University of Texas, Austin. It’s the relative concentration of these components that sports scientists have spent decades perfecting.

The salt and water help replace those same components lost in sweat, and the sugar gives athletes an energy boost. Dehydration causes a reduction in blood volume via osmosis, and decreased blood flow to the muscles and skin in turn leads to fatigue and impairs the body’s ability to dissipate heat. Carbohydrate, which is stored as glycogen in muscles, is burned during exercise, also causing fatigue.

Determining the ideal concentration of salt to put into sports drinks can be difficult because “there’s a compromise,” says George A. Brooks, a professor in the department of integrative biology at the University of California, Berkeley. “If you put too much salt in, it tastes bad,” he says. “If you don’t put enough in, it doesn’t replace what an athlete needs.” For this reason, sports drinks generally top off at about 20 mM sodium chloride—a concentration at the lower end of what people sweat out. Those endurance athletes who are “salty sweaters,” Coyle says, might even need to take supplemental salt tablets.

Salt intake becomes especially important when athletes sweat excessively. Taking in too much water and not enough sodium causes the blood to become dilute; excess water enters the body’s cells and tissues, including the brain, which can swell. Although this condition, known as hyponatremia, is rare, it can be life threatening, says Nancy J. Rehrer, an exercise metabolism expert at the University of Otago, in New Zealand.

Determining the optimal concentration and type of sugar to put into a sports drink is similarly challenging. “Putting sugar back into an athlete’s bloodstream often improves their performance,” Coyle says. But the more concentrated the sugar, the slower it leaves the stomach and enters the small intestines, where absorption primarily occurs, he explains. For practical purposes, most of today’s sports drinks are in the range of 4–8% carbohydrate, Coyle says.

So the “state of the art” in the sports beverage field “is to include as much energy solute in the drinks as possible without bogging the person down,” Brooks says. Because carbohydrate absorption is mediated through intestinal transport proteins, and there are different transporters for different sugars, investigators are now working to optimize various combinations of carbohydrates in their drink formulations. “You can saturate the transport capacity by loading up on a single metabolite,” Brooks explains.

Another way formulators are getting more carbohydrate into athletes’ systems is by adding glucose polymers, such as maltodextrins, to drinks. Brooks says, “That’s to keep the carbohydrate content high” while maintaining the beverage’s osmolality, or total solute concentration. Brooks himself has advocated this polymerization approach in developing his own energy substrate for sports drinks—polylactate. “Lactate is a major energy source for muscle,” he says. “It’s also a major substance that the liver uses to support blood sugar” and can help buffer the blood.

Because companies cram so much energy solute into their drinks, the average person doesn’t really need to use them during exercise—especially when trying to slim down. Sports drinks are great “for simple refreshment,” Brooks says, but as performance enhancers “these drinks really help athletes and people who are out there for an hour or more.”