Tag Archives: carbon dioxide

Practical phase changes: more carbon dioxide

9 Dec

I get to talk about an interesting application of carbon dioxide today in my latest article for Scientific American: sterilizing transplanted tissues such as tendon and bone. Before I heard about this technology, I certainly wouldn’t have suspected that the ubiquitous gas that we exhale could become a super-scrubber with a little heat and a lot of pressure.

I’ve ended up playing with a lot of carbon dioxide over the years. Like most kids, I had ghoulish carbon dioxide bubbles from dry ice that fizzed my Halloween drinks. As a chemist, dry ice became almost too “normal.” As an undergrad, I made my own bricks of the stuff from a tank of compressed CO2, and in graduate school, I’d weigh it out by the tens, if not hundreds, of pounds. Mostly, I used it to cool things down.

But though it’s easy as a working organic chemist to think  it cliché, watching the supercritical fluid form and dissipate is amazing. That sense of wonder within a high pressure chamber– and the practical applications that come from it– keep me coming back to work everyday.

Speaking of clichés, this professor probably fits the stereotypical scientist image a little too well. But I love his giddy enthusiasm when he talks about how he uses the demonstration to see whether a prospective student might be a good fit for his research group.


Of tomato plants, iPods and Darwin’s great-great granddaughter

29 Jun
my tomato plants in late June

my tomato plants in late June

Could a voice actually matter in making plants grow? Most of the scientific-sounding explanations I’ve ever heard about response of plants to people have invoked the additional carbon dioxide in the plants’ vicinity. But over the weekend I heard about an unusual study carried out by The Royal Horticultural Society. The researchers played different voices through headphones to 10 different plants over a period of a month (mp3 through headphones), according to the BBC. The best growing plants were listening to Sarah Darwin, a botanist and descendant of Charles Darwin. She read from her famous forebear’s groundbreaking text, On the Origin of  Species.

Of course, some outlets have taken this story to an extreme: Women’s voices ‘make plants grow faster.’

I can’t find the study, so I can’t see how it was constructed or how valid it is other than as an amusing anecdote with a connection to botany and Charles Darwin. My more skeptical side asks: Really? Headphones on plants? Where do you attach them? I’d really like to see a photo of a tomato plant with an iPod.

So I doubt that the study actually has much to say about how plants respond to human beings. However, if plants actually do like Sarah Darwin’s voice, I can understand why. Hear her melodious voice on the accompanying  video from the BBC.


Molecule of the Week: Carbon dioxide (part 1 of many)

28 Jun
Carbon dioxide (via Wikipedia by JacekFH) carbon atom in the middle flanked by two oxygen atoms

Carbon dioxide (via Wikipedia by JacekFH) carbon atom in the middle flanked by two oxygen atoms

This small molecule is too big for a single post, so I’ll probably revisit it at different points in this blog. It’s the most oxidized form of carbon, often thought of as waste product: both of fossil fuel burning and of the energy reactions that fuel life. But it’s also an essential component of photosynthesis to generate food and natural fuel sources.

But today I’m thinking about one of the many environmental impacts of rising atmospheric levels of carbon dioxide: the acidification of the oceans.

Changing the acidity of the oceans alters a delicate balance. Science suggests that this growing acidity may be dissolving carbonate in corals and releasing metal ions that would normally be wrapped up in carbonate minerals. (See this article in Chemical & Engineering News about the disrupted chemical balance).

The ocean has always been a giant sink for carbon dioxide, water absorbs it forming carbonic acid. Cooler water absorbs more carbon dioxide, but higher concentrations in the atmosphere are the primary force in pushing more of the gas to dissolve into the water, turning the ocean more seltzer-like (in terms of pH, not fizz).

coral reef in Red Sea, copyright iStockphoto/wierdeau

coral reef in Red Sea, copyright iStockphoto/wierdeau

The effects, however, are not always what one might expect. In looking at fish earbones, called otoliths, researchers reported in Science that higher carbon dioxide levels actually made these structures larger rather than smaller. (Cornelia Dean of the New York Times wrote about it on Andy Revkin’s Dot Earth blog).

Otoliths are the tree rings of fish life-cycles. What does this mean for the fish? Not necessarily good– changes in ear bones could mangle their navigations skills.

Of course all of this science sits around the edge of the passage of the American Clean Energy and Security Act (ACES) by the House of Representatives this week. There will be plenty of opportunities to talk more about carbon dioxide. . . . stay tuned.