Plastics - Chemistry Encyclopedia

The term "plastic" can be broadly defined as any inherently formless material that can be molded or modeled under heat and/or pressure. It is derived from the Greek word plastikos, meaning a shaped or molded substance.

Platinum - Chemistry Encyclopedia

The first reports of the discovery of platinum were the papers of Antonio de Ulloa, who found an unworkable metal, platina (Spanish for "little silver"), in the gold mines of Colombia in 1736. Charles Wood provided the first samples in 1741.

Plutonium - Chemistry Encyclopedia

Plutonium was discovered by Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl in 1940. They prepared a new isotope of neptunium, 238Np, which decayed by β-emission to 238Pu.

Polonium - Chemistry Encyclopedia

Polonium is a silver-grey, radioactive metal. Discovered by chemist Marie Curie in 1898, polonium was named after her country of origin (Poland).

Polyesters - Chemistry Encyclopedia

Polyesters are long chain synthetic polymers that have ester linkages. Polyester materials are used as fibers, plastics, and films; in composites and elastomers; and as coatings.

Polymerase Chain Reaction - Chemistry Encyclopedia

The polymerase chain reaction (PCR) is used to make millions of copies of a section of deoxyribonucleic acid (DNA). Until the 1980s obtaining numerous copies of a section of DNA took one to two weeks and required isolation of the DNA, cloning the DNA into a viral or plasmid vector, growing the cloned DNA using living host cells, usually bacteria, and finally isolating the DNA again.

Polysaccharides - Chemistry Encyclopedia

Polysaccharides are long polymers of monosaccharides and their derivatives. Unlike proteins or nucleic acids, these polymers can be either linear or branched, and they can contain only one type of monosaccharide (homopolysaccharides), or more than one (heteropolysaccharides).

Potassium - Chemistry Encyclopedia

Potassium is a soft, silvery alkali metal that reacts strongly with water to produce hydrogen gas. The word "potassium" is derived from "potash" or "pot ashes," as Humphry Davy isolated the element in 1807 via the electrolysis of caustic potash, KOH.

Praseodymium - Chemistry Encyclopedia

In 1885 C. A.

Primary Structure - Chemistry Encyclopedia

There are four recognized levels of protein structure: primary, secondary, tertiary, and quaternary. The primary structure refers to the amino acid sequence of a protein.

Promethium - Chemistry Encyclopedia

The existence of promethium was first theorized in 1902 by Bohuslav Brauner, who predicted that an element between neodymium and samarium was missing from the periodic table. Because only minuscule amounts of promethium are naturally present in Earth's crust, full confirmation of this prediction was not made until 1945.

Protactinium - Chemistry Encyclopedia

An isotope of protactinium (having mass number 234 and a half-life of 1.1 minutes) was first identified by Kasimir Fajans and O. Gohring in 1913 as a short-lived member of the naturally occurring 238U decay series and was given the name brevium, meaning brief.

Max Planck - Chemistry Encyclopedia

Max Karl Ernst Ludwig Planck was born into a family of lawyers and clergymen, and he became the fourth generation of university professors from his family. As a child, he exhibited considerable talent in mathematics, music, and philology (the scientific study of language).

Natural Polymers - Chemistry Encyclopedia

The word "polymer" means "many parts" (from the Greek poly, meaning "many," and meros, meaning "parts"). Polymers are giant molecules with molar masses ranging from thousands to millions.

Synthetic Polymers - Chemistry Encyclopedia

Polymers are large molecules composed of repeated chemical units. The smallest repeating unit is called a mer.

Joseph Priestley - Chemistry Encyclopedia

Joseph Priestley was a dissenting Unitarian minister in England at a time when adherence to the established Church of England was of great importance. Preaching was a difficult career for Priestley—because his Unitarian views were unpopular and because he spoke with a stammer.