MOLECULES AT AN EXHIBITION (Gallery 4)

Emsley, John.  Molecules at an Exhibition: The Science of Everyday Life.  New York: Oxford University Press, 1998.

This book is 272 pages in length (paperback version published by Oxford University Press).  In this book, the author presents the interesting chemistry of some of the substances we encounter in everyday life.  He groups these chemicals in galleries, much like artwork is grouped in museum or gallery collections. This book grew out of a series of popular news articles written by the author featuring a “Molecule of the Month”.  In this book, however, the author is able to take liberty to provide more details on the chemistry and a broader perspective of the role that the chemical plays in familiar materials.

Some of the information, especially those based on medical studies, are dated.  The author avoids giving more detailed precise chemical explanations to keep the discussion at the level of someone who does not have much chemistry background.  For example, in one instance, the author mentions that food high in oxalic acid such as spinach and rhubarb prevent the absorption of the magnesium because the oxalic they contain forms a compound that does not get digested but does not offer an explanation as to what this compound is and whether it complexes magnesium.

John Emsley lectured in chemistry for 25 years in the University of London and is the author of over a hundred research papers.  He has been a Science Writer in Residence in the Chemistry Department at the University of Cambridge.

For my notes, I am extracting interesting properties, chemistries, and anecdotes presented by the author for each compound featured and collect them in powerpoint slides.

GALLERY 1: NEARLY AS NATURE INTENDED

This gallery features natural compounds found in food and their interesting properties, with names that make them sound “unnatural”.  One of these compounds is not a natural compound but rather a synthetic one associated with plastics (phthalates). The following compounds are featured in this gallery:

• phenylethylamine in chocolate
• oxalic acid in rhubarb pie
• caffeine and phosphoric acid in Coca-Cola
• phosphoric acid in rust remover
• dipropenyl disulfide in garlic
• methyl mercaptan as a metabolite and odorizer in natural gas
• selenium in Chinese medicine
• salicylates in food and in aspirin
• phthalates in plastics

GALLERY 2: TESTING YOUR METAL

In this gallery, the author describes interesting metals that are essential for human growth and function.   There are a total of fourteen metallic elements needed by the body for normal functioning: Ca, K, Na, Mg, Fe, Zn, Cu, Sn, V, Cr, Mn, Mo, Co, Ni.  However, there are also other metals found in an average adult that have no known uses in the body:  Al, Ba, Cd, Cs, Pb, Ag, and Sr.  Trace amounts of U and Au (about 7 mg) have also been measured.  Some of these, like Sr (about 320 mg), resemble the chemical reactivity of an essential element like Ca and so our body tends to absorb and keep them. An interesting tidbit about U, up to 0.07 mg have been measured in the average person; this small amount can power a car to run for five kilometers.  Our bodies tend to retain U because of its affinity for phosphate a while Au attaches to proteins in the liver.

Calcium leads the 14 essential metallic elements in mass.  A typical 70 kg adult has about 1 kg of Ca, 99% of which are in the bones.  Of the 9 kg of bone, about 1 kg of this is calcium and 2.5 kg is phosphate; the rest are water, collagen, and other elements such as sodium, potassium, iron, copper, and chlorine.  Lead can sometimes be found because of its attraction to phosphates.

Metals and compounds featured in this Gallery:

• calcium phosphate in the bone
• sodium chloride
• potassium chloride
• iron
• magnesium
• zinc
• copper
• Tin
• Vanadium
• Chromium
• Manganese
• Molybdenum
• Cobalt
• Nickel

GALLERY 3: STARTING LIVES, SAVING LIVES, SCREWING UP LIVES

An exhibition of molecules that can help and harm the young.

In this gallery, the author features compounds whose presence or whose absence is important in creating healthy babies.

·        Folic acid

·        Arachidonic acid

·        Nitric oxide

·        Keratin

·        Mistletoe

·        Penicillin

·        Ecstasy

·        Cocaine, heroin, and designer drugs

·        Nicotine

·        Epibatidine

·        Melatonin

GALLERY 4: HOME SWEET HOME

An exhibition of detergents, dangers, delights, and delusions

In this Gallery, the author presents chemicals that are commonly found at home and touts that our homes are “cleaner because of detergents, healthier because of disinfectants, and safer because the chemical we use may be protected by other chemicals”.  Throughout the 1960-80’s, detergents were considered pollutants because they cause eutrophication, a chemical imbalance in natural waters that caused the over-production of algae and weed, attributed to the phosphates released from detergents.

The substances featured in this gallery are:

·        Surfactants

·        Phosphates in detergents

·        Perfluoropolyethers

·        Sodium hypochlorite

·        Glass

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