And You Thought You Were Under Pressure!

High-pressure Research Techniques Are Useful in Industry, Medicine

When the pressure gets to be too much, something has to give. That's as true for molecules as for anything else, and scientists like Ian Butler at McGill University in Montreal are studying just what gives at that level-how molecules change their shapes and crystals change their structures.

Have you ever over-pressurized your bicycle tire and experienced the result? That much pressure (approximately 600 kpa-six times the standard atmospheric pressure) is powerful, but it is miniscule compared to the amount of pressure found at the centre of the earth (3.6 x 108 kpa-about 3.6 million times greater than atmospheric pressure).

Now, pressures close to what is found at the earth's centre can also be created in the laboratory. It is done with diamond-anvil cells (two small diamonds pushing toward each other in a piston and cylinder device, with the sample to be studied put in a tiny opening between them).

Butler and his research group are studying the effects of such extreme pressures. They look at what the pressure does to the bonding between carbon and metal atoms, to the structures of important industrial ceramics, and to so-called "plastic crystals"-organic crystals whose molecules rotate freely at room temperature.

One of these plastic crystals is the recently-discovered Buckminsterene C60 (or "buckyball" to its friends). This carbon molecule is shaped exactly like a soccer ball; since it also looks like a geodesic dome, it was named after Buckminster Fuller, the dome's designer.

Right now, research scientists are the people most interested in the effects of such high pressure, but the diamond- anvil, high-pressure technique may also have important practical uses outside the laboratory.

One such use is likelv to be of interest for industry. French scientists have discovered that when buckyball is rapidly compressed to about 200,000 times atmospheric pressure at room temperature, it instantly transforms into polycrystalline diamond. Graphite will do the same thing, but only under much greater pressure or when heated above 1200 K in the presence of a catalyst.

Another application of this technique could save lives. Researchers at the National Research Council of Canada have discovered that when a sample of colon tissue is put inside the high- pressure chamber, changes in its infrared spectrum can indicate whether the tissue is cancerous or not.

High-pressure tactics are not always a good idea. But in the laboratory, they can lead to amazing results!

Searching the skies with a National Research Council telescope in the late 1970's. English chemist Harold Krote and a team of Canadian scientists were surprised to find many more molecules containing carbon chains than they expected. This astronomical puzzle eventually led Krote and American chemist Richard Smalley to the discovery of Buckyball.