Developments in Chemistry and Physics

DEVELOPMENTS IN CHEMISTRY AND PHYSICS

The Genesis of Modern Plastics

The decade from 1910 to 1919 was notable for many discoveries that would lead to startling technological advancements later in the century. One of the most notable developments was the beginning of the modern age of plastics, which originated with the work of the Belgian-born American chemist Leo Hendrik Baekeland. As is the case with many important breakthroughs, Baekeland's discovery was serendipitous. Chemists in 1909 often faced the difficult problem of removing chemical residues from their equipment, and Baekeland thought that he might be able to invent a solvent that could do the job. But first, because he did not have any chemical residue at hand, he set about creating some difficult residue to experiment on by combining phenol with formaldehyde. When he tried to dissolve the substance he created, no solvent worked. It then occurred to Baekeland that the substance he had created might itself have useful applications, and he set about improving the resinous mass to make it harder and tougher. Placing the reagents under suitable temperatures and pressures, he discovered that he could create a liquid that when cooled took on the shape of its container. He named the resultant plastic after himself, and Bakelite, marketed in 1917, was the first thermosetting plastic (a plastic that will not soften under heat once it has set).

Neon Lights

In 1910 the French chemist Georges Claude demonstrated that electricity passed through noble gases (monoatomic, chemically inert gases, also called inert gases) produced light. The red light produced by running an electrical current through neon produced the most spectacular result. Glassmakers and advertising executives soon recognized that glass tubing filled with neon and shaped into letters could be used as those bright roadway signs that advertise shops.

Superconductivity

In 1911 H. Kamerlingh Onnes, a Dutch scientist, unexpectedly discovered superconductivity in his Cryogenic Laboratory at the University of Leiden. He found that at temperatures approaching absolute zero metals lose resistance to the flow of electric current. Once a current is started in such a supercooled metal, the electron flow will continue almost unimpeded. For his discovery Onnes won a Nobel Prize in 1913. European and American scientists would continue to search for methods and materials that could expand the practical applications of superconductivity.

X-Ray Crystallography

The German physicist Max von Laue demonstrated in 1912 that when X rays were passed through crystal structures they were scattered in discrete patterns that could be identified on photographic plates. English physicists William Henry Bragg and his son William Lawrence Bragg successfully argued that the patterns on the photographic plate could be used to identify the exact location of atoms in the crystal. The science of crystallography was born. Laue won the Nobel Prize in physics in 1914 for his discovery.

Sonar

French physicist Paul Langevin revolutionized oceanography with the invention of sonar in 1917. In 1880 Pierre Curie had discovered the piezoelectric effect, which he demonstrated could generate ultrasonic sound waves. Langevin reasoned that ultrasonic sound waves (sound waves of extremely short wavelengths) would reflect off objects and bounce back to the sender. (Common sound waves are much longer than ultrasonic waves, bend around physical obstructions, and reflect back to the observer less efficiently.) The time it takes for the emitted ultrasonic waves to travel to the reflecting object and return could be used to fix the distance of the object. Since ultrasonic sound can easily travel through water, Langevin's sonar worked superbly to detect schools of fishes well as German submarines (a serious problem to Allied shipping interests during World War I). Today sonar is used by fishermen to find their prey and by oceanographers to map the ocean's floor.

Sources:

William H. Bragg, X-Rays and Crystal Structure, in Physical Sciences, volume 7, edited by W. L. Bragg and G. Porter (Amsterdam: Elsevier, 1970);

Tibor Zoltai and James H. Stout, Mineralogy: Concepts and Principles (Minneapolis: Burgess, 1984).