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Champagne may be the elixir of celebration, but for something so closely tied to joyous events, champagne is mercilessly encumbered by laws. The Appellation d’Origine Contrôlée outlines 35 of these rules conceived to uphold the quality of Champagne wines. It also defines the region of Champagne, an 84,000-acre area about an hour’s drive east of Paris. This demarcation separates champagne from other sparkling wines made with the “méthode champenoise.” According to the appellation, if the grapes weren’t grown in Champagne, the wine isn’t champagne.

From a chemical perspective, though, champagne and all other sparkling wines must conform to just one law, Henry’s law: The amount of gas dissolved in a fluid is proportional to the pressure of the gas with which it is in equilibrium. This dissolved gas–carbon dioxide in the case of champagne–gives the wine its characteristic effervescence. In an unopened bottle, CO₂ gas dissolved in the wine is in equilibrium with gas in the space between the cork and the liquid. Uncorking the bottle releases this headspace gas and disrupts the equilibrium. Following Henry’s law, the dissolved CO₂ leaves the wine via bubbles, reestablishing the equilibrium through effervescence.

Champagne makes its gas naturally during fermentation. Yeast turns glucose from grape juice into CO₂ and ethanol. The same fermentation process occurs in all wines, but valves on the casks let winemakers release the CO₂ so that it doesn’t build up.

Champagne gets its characteristic bubbles by trapping CO₂ gas while in its bottle, where it ferments a second time.

Visit “What’s That Stuff” to learn more about the chemistry of champagne.

Excerpted with permission, Chemical & Engineering News
Copyright © 2004 American Chemical Society

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As the year comes to a close, we often look back over the previous year at triumphs and disappointments, laughter and tears. Many of those memories are captured through the combination of art and science known as photography.

Historically, the concept of the camera obscura, in which an image was projected through a small opening onto an opposite surface, was well established by the 1800s. Indeed, in the late 1400s and early 1500s, Leonardo da Vinci wrote about natural examples of the centuries-old concept in his papers collected in the Codex Atlanticus.Photography, which means “drawing with light” in Greek, was born when the image from the camera obscura was fixed permanently on a surface, such as a sheet of photographic paper. Chemistry provided key components in the evolution of this technology.

The general principle is reasonably straightforward. First, a surface such as paper or a piece of metal is coated with a substance that will react with light. After the surface has been exposed to the image, a process is required to remove the unreacted photo-sensitive material so that the areas of light and dark are preserved. French inventor Joseph Nicéphore Niépce took the first photograph by using a pewter plate coated with bitumen, which hardened upon exposure to light, and allowed unhardened regions to be washed away. Louis Daguerre, first in collaboration with and then carrying on the work alone after Niépce’s death, refined the process of using silver nitrate to capture an image since silver compounds darken upon exposure to light. Daguerrotype photography used a silver coating on a copper plate to capture the picture. 

Numerous subsequent developments refined the chemical process of recording and preserving an image. George Eastman played a significant role in making photography both convenient and accessible to a wide and appreciative public. He patented film in roll form in 1884 so that photographers no longer needed to carry around bulky glass photographic plates. In 1901, his Kodak camera, the Brownie, made photography accessible to everyone. 

Photography is now mostly carried out using digital cameras, but chemistry historically was the heart of this process that we use to capture moments and memories. For those photographic artists who still develop their own images, the process remains as much about the chemistry as about the art. 

An excellent historical retrospective on the history of photography may be found at http://photography.nationalgeographic.com/photography/image-collection/#/history_of_photography/

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The chemists who create perfumes consider their work as much of an art as a science. They speak of the combination of smells as composed of ‘fragrance notes’ the way a pianist describes musical chords.

The top notes are small, light molecules that are the most volatile components of a perfume. They are the first smells to reach a person’s nose and as such are usually what convinces a person to select a particular scent in a store. The middle notes are chosen to start releasing just as the compounds of the top notes dissipate. Often referred to as heart notes, these compounds also mask the initial scent of the base notes, which may be initially unpleasant, but become appealing over time. Base notes, compounds which tend to start evaporating after half an hour or so, provide a perfume’s richness and depth. Together with the middle notes, base notes form the theme of a fragrance, which may be characterized, such as floral, citrus, fruit, or ocean.

Aromatic compounds used to make modern perfumes come from both natural and synthetic sources. In addition to flowers, which form the most common, most familiar group of perfumes, other plant products may also be used. Cinnamon bark, rosemary and lavender leaves, and the seeds of cocoa and anise are popular. Sandalwood, cedar, and pine are derived from their respective woods. Fruits scents such as apple, strawberry and raspberry cannot be directly extracted, so these aromas are nearly always produced from synthetic components.

It is not uncommon for perfumes based on natural products to contain hundreds of compounds that together contribute to a subtle scent, whose character may vary depending on the season, time of day, and weather conditions in which the natural materials were harvested. Synthetically produced compounds yield more reliable formulations with purer, more pronounced fragrance notes. Synthetic organic chemistry also provides scents that are not found in nature for a more unusual fragrance.

With so much variability and complexity, the perfumer’s workbench appears not unlike an organ console. The tools are an array of aromatic chemical compounds that the chemist may play to develop a harmonious theme for nose and heart. 

More information about the history and composition of perfumes may be found at http://www.perfumes.com/eng/history.htm

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Gum, perhaps the world’s oldest confection, began as an edible treat from trees. Although far less sweet than today’s gums, a chewy tree sap called mastiche was a favorite of the ancient Greeks. Its name derived from the Greek word mastichan meaning “to chew.”

On the other side of the world, the Mayans enjoyed chewing on tsictle, the sap of the sapodilla tree (Manilkara zapot). Farther north, Native Americans living in what is now New England enjoyed the sap of spruce trees (Picea genus). Spruce-sap chewing gums were first brought to the U.S. market in the mid-1800s by entrepreneur John Curtis, who sold small sticks of “Maine Pure Spruce Gum.”

Spruce-sap-based gums were later replaced by those made with petroleum-derived paraffin wax. Gum makers added sugar to their paraffin gums to increase their sweetness. Such gums were sweet but not chewy enough. For the right level of chewiness, gum makers turned to an old favorite: tree sap. The Mayans’ tsictle-called “chicle” in the U.S.—came to dominate the gum market.

 Another American inventor, Thomas Adams, proved chicle was no substitute for rubber. However, Adams and his sons found that heating chicle with sugar and flavor yielded a gum superior to paraffin-based predecessors. Chicle gum in hand, Adams got a patent for a gum manufacturing machine and founded Adams Sons & Co. in the 1870s. Americans were soon chewing Blackjack, the first flavored gum.

Visit “What’s That Stuff” to learn more about the history and chemistry of chewing gum.

Excerpted with permission, Chemical & Engineering News
Copyright © 2007 American Chemical Society

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Chemistry has not only played a role in making glass, glass has played a prominent role in the progress of chemistry through glass flasks and beakers, glass wool to insulate reactions, and optics for instrumentation.

The primary component of glass is silica, SiO₂, which may be used in a pure form to yield fused quartz, but extremely high glass transition temperature of this material makes it challenging to work with.  Various additives such as sodium carbonate are added to the silica to reduce the glass transition temperature with additional ingredients of lime, aluminum oxide, and magnesium oxide used to make glass that is more chemically durable.  This mixture, known as soda-lime glass, is the composition of 90% of manufactured glass.

Borosilicate glass, known as Pyrex, is a combination of silica and boron oxide.  This material has a low thermal expansion coefficient which makes it less prone to cracking when exposed to extreme temperature changes, so it is useful for laboratory beakers and household cookware. 

It is a common myth that glass continues to flow over time with evidence being cited that many older windows are thicker at the bottom than at the top.  This variation actually arises from the historic process used to form plate glass which involved spinning the glass into a sheet.  The material on the outer edge was thicker than the inner glass, which resulted in the slightly uneven distribution.  When mounting the glass in a window frame, the thicker edge was placed at the bottom to ensure stability.

Certainly some of the most spectacular applications of glass are in the area of art and architecture.  Louis Comfort Tiffany made his name as a master of stained glass whether in lamps or in windows, and he experimented with different methods of imparting glass with color and texture.  Artists such as Dale Chihuly create magnificent sculptures similarly using glass to explore form and hue.

 More information about the techniques and history of glassmaking may be found at http://www.sha.org/bottle/glassmaking.htm

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Whether it be the bright flavor of candy canes or the zing of peppermint schnapps that warms up your hot chocolate, for many people peppermint is often associated with winter and the holidays. The most popular member of the mint family, peppermint is also the flavor found in those red and white striped starlight mints that finish off many a restaurant meal.

Peppermint was originally classified in 1753 by Carolus Linneaus as its own species, but eventually scientists determined it was a hybrid plant derived from a cross between spearmint and watermint. The failure to produce viable seeds, however, does not prevent this plant from spreading aggressively via underground rhizomes, thus earning the reputation as a highly invasive plant in the United States, New Zealand, and Australia.

Peppermint leaves, although delicious in tea, are not always a convenient form for the flavoring, so the plant is processed in several ways to provide that minty fresh taste.  Peppermint’s essential oils, which include menthone, menthyl esters, and trace components such as limonene, eucalyptol, and pinene, can be concentrated through steam distillation to yield oil of peppermint.  The oil is the most concentrated form of the flavoring, so only a drop or two is needed in making candy, chewing gum, and toothpaste.  Peppermint extract, isolated by alcohol distillation of either the leaves or of the oil, is a more dilute preparation, which is often used in baked goods.

The peppermint-flavored liqueur, crème de menthe, is traditionally made by steeping dried peppermint leaves in grain alcohol for several weeks. This naturally green liquid is then filtered and sweetened with sugar to make the basis of cocktails such as the grasshopper. A stinger martini uses brandy and white crème de menthe, which is made from the extract rather than the leaves.

More information about the use of peppermint as a natural medicine is available at http://www.umm.edu/altmed/articles/peppermint-000269.htm

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Christmas morning.  The balsam scent of evergreen boughs fills the air as the kids tear open a new Game Boy powered by the chemistry of tiny batteries.  The aromas of gingerbread and cinnamon waft in the background as a teenager plans to try out a new snowboard constructed of advanced fibers made by chemists. Adults sniffing hopefully for a breakfast of coffee and stolen as future scientists investigate a long-awaited chemistry set.  Although chemistry may have contributed to many of the items on our wish lists, the celebration of Christmas especially resides in the aromas and scents of the holiday and in how those scents invoke our memories

When the nose detects an aroma, the information is passed along to the limbic system of the brain, which includes such structures as the hippocampus and the amygdala. The limbic system not only supports the sense of smell, but it is also responsible for emotion and long term memory, thus creating strong links among these functions. Sights and sounds may invoke memories from any point in a person’s life, but scents frequently trigger strong emotional memories of childhood.  In the limbic system, aromas form the strongest associations the first time they are encountered rather than being replaced by later connections. Given that children experience so many smells for the first time, it is these memories that are invoked, consciously and sometimes unconsciously, when a scent is experienced years later. Many adults find that the scent of a particular perfume or cologne summons the memory of a loved one or a special moment from times gone by.

Thus, it is that our brains are particularly adapted to associate the emotions and connections of this holiday with the aromas and memories of Christmases past. So, let the scents of frankincense and myrrh, of evergreen and mistletoe, of snow, of poppy seed milk, of fruitcake, of pomander balls made with oranges and cloves, of peppermint, and of cookies baking – whatever smells you associate with Christmas – bring you happy memories on this special day.

Merry Christmas!

Two discussions of the connection between scent and memory may be found at http://www.nytimes.com/2008/08/05/science/05angier.html and http://www.cell.com/current-biology/abstract/S0960-9822%2809%2901857-0

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In 1950 the United States Government embarked on a search for peacetime applications for atomic energy. The most promising application was the nuclear power reactor, seen as an abundant source of clean energy. To extend the value of reactors to the commercial sector, the government funded research on uses for the radioactive by-products of reactor operations.

As part of that research, the reactor Development Division of the Atomic Energy Commission sponsored a study at the newly created Stanford Research Institute (SRI) in Palo Alto, California. The purpose of the study, supervised by 25-year-old chemical engineer Paul Cook, was to determine the potential industrial uses of waste fission products — alpha emitters, beta emitters, and gamma ray producers.

The study concluded that there were limited industrial uses for waste fission products. However, as a result of these studies and subsequent experiments conducted by Cook at SRI and elsewhere, he became convinced that radiation could be used to develop new materials for industrial applications. When a reliable, low-cost source of ionizing radiation became available, Cook — with James B. Meikle and Richard W. Muchmore — founded the first company based on radiation chemistry, the field of knowledge concerned with the chemical effects of radiation on different materials. Cook and the employees of the company that became Raychem Corporation proved the commercial value of treating and altering the chemical structure of polymeric products in their final form, giving them special properties and characteristics that could not be easily created using any other method.

Visit National Historic Chemical Landmarks to read more about the commercialization of radiation chemistry.

Excerpted with permission, National Historic Chemical Landmarks Program
www.acs.org/landmarks

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Paul B. Weisz (b. 1919) pioneered the use of natural and synthetic zeolites (hydrous silicates) as catalysts while he was working at Mobil Oil (now ExxonMobil). These catalysts are highly selective, facilitating only certain reactions between specific molecules of given shapes. Processes based on zeolite catalysts were first developed in the 1960s and were found to increase both the amount of gasoline obtainable from petroleum and the octane rating of gasoline. Shape-selective zeolite catalysts proved to be widely applicable to many other industrial processes, including the manufacture of gasoline from natural gas and the production of raw materials for making polyester garments, plastics, and other products from petroleum.

Not until after he had become a well-established researcher in catalytic chemistry did Weisz achieve his long-deferred goal of a doctoral degree at the Eidgenössische Technische Hochschule in Zürich, Switzerland, while on a leave of absence from Mobil. His thesis on the mechanism of dyeing fibers developed some of the basic laws about the entrance of dyes into fibers, based on his experience with the velocity with which chemicals flow into catalytic materials.

Visit Chemistry in History to learn more about Paul B. Weisz.

Excerpted with permission, Chemical Heritage Foundation
www.chemheritage.org