... And bigger crystals in space.

. . . and bigger crystals in space

The date March 30, 1992, already means a lot to chemical engineer Albert Sacco Jr., of the Worcester (Mass.) Polytechnic Institute. That's when shuttle flight STS-53 is scheduled to launch crystallization experiments dreamed up eight years ago by Sacco and a now-deceased friend. Moreover, as a mission-specialist candidate, Sacco himself may fly into space that day.

The experiments involve zeolites, a class of labyrinthine crystals with catalytic, porous networks, used in such technological applications as "cracking" large petroleum molecules into the smaller ones that make up gasoline. On Earth, gravity, vibrations, temperature fluctuations and other factors limit chemists to growing micron-sized zeolite particles.

Space, in theory, should be nearly free of crystal-wrecking factors. But previous efforts to grow crystals in space have yielded mixed results, Sacco says. In most cases, more tiny crystals formed rather than a few larger crystals.

He and his co-workers have now developed a chemical trick, which they hope will enhance crystal growth at the expense of crystal number. By adding metal-binding molecules such as tetraethanolamine (TEA) to the crystallization solution, the researchers can continuously regulate the amount of an aluminum-containing zeolite constituent, Sacco says. TEA grabs on to these constituents and, like a time-release capsule, frees only small amounts of them at a time. The freed aluminum constituents, he says, add to an already initiated zeolite crystal more readily than they help to initiate a new crystal.