Computer Test Tubes

Despite neat formulas and equations in textbooks, chemistry is still an inexact science. At best, scientists only partly understand some of the turbulent processes that occur during chemical reactions; often they cannot accurately predict the end results. Now a California scientist has devised a method for making chemistry more exact: he mixes chemicals in a computer instead of a test tube.

Enrico Clementi, a theoretical chemist at IBM's San Jose research laboratory, was familiar with the mathematical descriptions of the actions of the electrons, nuclei, atoms and molecules that participate in a chemical reaction. He was certain that a solution of all the equations involved would give a mathematically precise picture of any chemical reaction. But how could he possibly manage the hundreds of billions of forbidding mathematical steps required for the solution? To an IBM man, the answer was obvious.

TV Cross Section. Clementi and other IBM scientists stuffed the memory of an advanced computer with equations that described a number of different atoms. Having set up what, in effect, was an electronic chemistry lab, Clementi ordered the computer to produce the mathematical specifications for one molecule of ammonia and one of hydrochloric acid. The obedient computer was then told to move the two molecules together gradually until they combined to form ammonium chloride (commonly called sal ammoniac), a chemical found in such varied products as cough medicines and battery electrolytes.

As the mathematical molecules began to interact, the computer sketched them in bright, sharp lines on a television screen. For the first time, scientists were able to examine a cross-section view of the orbits of electrons during a chemical reaction. By ordering the computer to slice through the ammonium chloride molecule at different angles, Clementi developed other cross sections; he was also able to determine exactly how the atoms in the molecule were joined.

Inaccessible Reactions. While it was providing visual information, the computer was also spewing out torrents of printed data describing the energy that binds together a molecule of sal ammoniac. It also spelled out the temperatures and pressures at which the chemical can exist. To Clementi's surprise, the computer revealed that at a temperature around 1300DEGF--and at high pressure --sal ammoniac, which was previously believed to exist only as a solid, could also be a gas. Two University of Brussels chemists have since produced sal-ammoniac gas in their laboratory, using the computer data for guidance.

Chemist Clementi firmly believes that test-tube computers will bring new precision to chemistry. They will also enable scientists for the first time to study otherwise inaccessible chemical reactions that occur in the extreme temperatures of rocket engines, for example, or under the stupendous pressures at the center of the earth. "In safety and at their leisure," says Clementi, "they will be able to produce these reactions in a computer that will not melt in the heat or collapse from the pressure."

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