Archive for February 2013

It’s Heavy Stuff

History and science have always interested me for the same reason: these subjects explain why things are the way they are. They just explain different types of things. Sometimes they’re more intricately connected than one might expect. Chemistry is connected to many minor historical events, for example the fall of the Roman Empire. Yes!

Lead has the chemical symbol Pb and the atomic number 82 on the Periodic Table. It’s atomic mass is 207.2 and it melts at 621.5°F (327.5°C), which is relatively low for a metal (compared to gold (Au) which melts at 1,948°F (1,064°C)). It’s classified as a heavy metal. Some of the common effects of lead poisoning, many of which are common to all types of heavy metal poisoning, include the appetite loss, abdominal pain, colic, pallor, weight loss, depression, fatigue, irritability, and nervous spasms. Also, eventually you’ll go crazy because it affects the nervous system. It’s not fully understood by what mechanism heavy metals affect the nervous system, but it may have something to do with the enzymes responsible for distributing important minerals throughout the body, such as Calcium and Selenium (1). So, you can see why consuming this type toxin could be disruptive to a society.

File:Electron shell 082 Lead - no label.svg

Diagram of a Lead Atom

Our love of lead began a long, long time ago. It was one of the easiest metals to work with and extract from natural ore because of its low melting point and abundance in the earth’s crust. The oldest known lead object is from Turkey (circa 6,500 B.C.), and pottery from Ancient Egypt (3,000-4,000 B.C.) has been found glazed with lead. Lead has been used for everything from furniture decorations to stained glass window frames in churches and cathedrals. Its use has had endless repercussions on history, so I’ll touch on the highlights.

File:Lead(II)Acetate.jpg

Not Sugar!

Lead (II) Acetate, chemical formula Pb(CH3COO)2, also known as “sugar of lead” was used by the Ancient Romans as a sweetener for food and beverages, particularly wine (2). That was long before anyone was sailing over to the Americas and bringing back cane sugar. As if running your drinking water through lead pipes wasn’t enough, they went right ahead and added the stuff directly to their diet, sometimes even sprinkling the crystals on dishes like a spice. Good plan.

Lead compounds were also commonplace in colonial times:

During the Colonial Period, in addition to the trade in rum, there was extensive manufacture and use of glazed earthenware, pewter, lead pipe, lead shot, and lead type for printing. Red and white lead were widely used as pigments for paints (also as an addition to red pepper); lead acetate and lead oxide were used to sweeten and whiten bread. Litharge (a PbO product) was used as a putty to install windows and, according to colonial records, was sometimes added to snuff. Apparently, lead intoxication was rampant during the Colonial Period in America and may have been involved in accusations of witchcraft because individuals with lead poisoning neu- ropathy often show weird behavior (3).

Lead Figure of an Ancient Goddess, from Sparta

People long suspected that lead had negative effects on health, based on their observations of those who worked directly with it, such as miners or potters. Yet, time and time again, despite the difficulties of Roman emperors (notably Julius Cesear and his successor, Caesar Augustus) had producing children, the observations of Greek physicians, the warnings of Benjamin Franklin and even the U.S. government, people continued to use it in all sorts of self-destructive ways. In 1473, a publication entitled “On the Poisonous and Noxious Vapors and Fumes of Metals” was authored by U. Ellenberg, but the United States Congress waited until 1970 to pass the Occuptational Health Act to regulate lead in food packaging and the environment.

File:Benjamin Franklin 1767.jpg

Benjamin Franklin

I was shocked to learn that leaded fuel was available until the 1990’s, and that a 1980 report from the National Academy of Sciences estimated that Americans were using about 11 pounds of lead per person each year. The General Motors engineers who developed the leaded fuel met the same fate that many exposed to lead had met before,

As many as fifteen workers who helped produce the additive in refineries in Ohio and New Jersey fell sick and died. In most cases, mental derangement preceded death, and many of the workers died in straightjackets. Nearly 300 workers from three plants were pronounced psychotic, and workers and journalists soon began to call leaded fuel “loony gas.” For the next six decades, as many as 5,000 Americans died every year from lead poisoning, according to a 1995 EPA report (4).

I had no idea that lead use was and is such a big deal. Some researchers estimate that 7 million tons of lead from burnt gasoline remain in the United States ecosystem. But, hey, at least we’re not using it as a condiment anymore.

Thanks for reading,

-Ashley

 

More information about lead and the environment can be found here. And the links in the sources are also worth checking out.

Also, this:

 

Sources

(1) http://www.ncbi.nlm.nih.gov/pubmed/19644200

(2) http://www.vias.org/genchem/inorgcomp_leadacetate.html

(3) https://kb.osu.edu/dspace/bitstream/handle/1811/23252/V088N3_078.pdf?sequence=1

(4) http://www.dartmouth.edu/~toxmetal/toxic-metals/more-metals/lead-history.html

 

 

 

 

All About….Chocolate! (Need I Say More?)

In or out of love, I think anyone can appreciate the annual Valentine’s Day-induced chocolate craze. I recently learned that this week is officially chocolate week in New York City (makes sense). London also has a chocolate week, from the 8th to 14th of October (does not make sense). But, I mean, it’s chocolate. There doesn’t have to be a holiday or good reason to eat it.

Or does there?

Chemistry says that there is a reason to eat chocolate, or at least reasons we like to.

Chocolate has been claimed to have all kinds of effects on the body and mind, including being a stimulant, relaxant, euphoriant, aphrodisiac, tonic and antidepressant. That’s a pretty impressive resumé. Although there are about 380 compounds in chocolate, only a few have been identified as potential sources of our cravings (5). I always thought that caffeine was the main active compound found in chocolate, but apparently there are other chemicals that play much larger roles in its feel-good properties.

Some of these properties originate from a class of chemicals called methylxanthines. Methylxanthine is what caffeine, theobromine and xanthine are derived from, all of which are found in chocolate. Of the three, theobromine is the big player in chocolate. This study found that the average cocoa powder contains 1.89% theobromine and only 0.21% caffeine. In fact, one variety of cacao plant is actually called Theobroma Cacao (a name derived from Greek meaning, “food of the Gods.” Seems appropriate.). Another study compared how much volunteers’ preferences increased for a mystery drink plus placebo pill, versus a mystery drink plus methylxanthine-containing pill. They found that the drink paired with the chemical was significantly better liked over the course the experiment. The prescence of these compounds must have something to do with our craving for chocolate. So, what exactly is this magical theobromine?

A Theobroma Cacao tree….give thanks.

Theobromine is an alkaloid. Alkaloids are basic compounds that usually contain a Nitrogen atom, and a ring in their structure. They’re often associated with poisonous or addictive things, like nicotine and morphine (because they are also examples of alkaloids) (1). Alkaloids are the reason that dark chocolate tastes a little bitter (see also: black coffee). But, don’t let its alkalinity scare you off.

Like caffeine, theobromine is found in coffee and tea in smaller amounts than in cacao products. In fact, caffeine and theobromine have very similar molecular structures. The only difference is that one molecule (theobromine) has a Hydrogen atom (H), and the other (caffeine) has a methyl group (a Carbon attached to four Hydrogens) on the end (2). Similar molecular structures mean they do some of the same stuff to your brain, like make you more alert (5). Weirdly enough, theobromine lowers blood pressure whereas caffeine actually increases blood pressure (3). So, similar, but not the same. Our brains are very particular (thank goodness).

[Total Side Note: Research is being done to see if theobromine consumption is an effective treatment for asthma symptoms because theobromine is also a cough suppressant (4). I’ve been wondering since I read that if being sick is an excuse to eat lots of chocolate. Then again, most things are excuses for eating chocolate.]

It’s no coincidence that chocolate is craved by women more than any other food, and the average American eats 11 pounds of the stuff each year (5). This article from CNN health provides some interesting hypotheses about chocolate and mood. A compound called anandamide (a.k.a. the “bliss molecule”) is found in chocolate. It activates some of the same parts of the brain that marijuana does (the part that makes dopamine), but to a much smaller degree. Not only does it contain this chemical, but researchers from the Neuroscience Institute of San Diego suspect that some components of chocolate prevent feel-good anandamide from breaking down in the brain. In addition to speculation about the anandamide content of chocolate, scientists have studied the effects of chocolate on serotonin levels in the brain.

Serotonin is a neurotransmitter, which is any molecule that carries messages through your brain, such as when it’s bedtime or how happy you feel. Specifically, low levels of serotonin can cause depression. One chemical in chocolate (tryptophan) causes the brain to release extra serotonin, which generally results in a better mood. Personally, I’m skeptical that it may just improve my mood because it is delicious.

Finally, chocolate also contains a chemical called phenylethylamine. It’s related to amphetamines.  Phenylethylamine is similar to amphetamines in that consuming it results in lower blood pressure and higher blood-sugar levels. This makes you feel more alert, fine, and dandy.  It also makes you feel like you’re in love as a result of a quickened pulse (5). Just in time for Valentine’s Day <3

It’s been a month since New Year’s, right?

There’s the evidence. As if the taste wasn’t enough……

I hope you enjoyed this post on the chemicals in chocolate : ) Please leave comments or questions, and enjoy some hot cocoa before it’s too warm.

 

-Ashley

 

Bonus! A chemistry activity website for your spare time: http://pbskids.org/zoom/games/kitchenchemistry/index.html

 

Sources

(1) http://www.thefreedictionary.com/alkaloid

(2) http://www.hersheys.com/nutrition-professionals/chocolate/composition/caffeine-theobromine.aspx

(3)http://www.sciencedirect.com/science/article/pii/S0031938411003799

(4) http://www.rsc.org/chemistryworld/podcast/CIIEcompounds/transcripts/theobromine.asp?playpodcastlinkuri=%2Fchemistryworld%2Fpodcast%2FCIIEcompound.asp%3Fcompound%3DTheobromine

(5) http://faculty.washington.edu/chudler/choco.html